‘ LIBRARY Michigan Sate University '4' ‘3' Imam; IV 7 T HUAG & SONS’ 800K BINDERY ’lllli. LIBRARY [INDERS mm. a lets-222*: ABSTRACT THE EFFECT OF FATNESS, CHILLING RATE AND SEX GROUP ON QUALITATIVE PROPERTIES OF BOVINE CARCASSES By Hsiang Chia Lee Ten cows, 10 Holstein steers, 10 bullocks and 20 beef-type steers were included in this study. Each sex group of cattle was divided into two fatness groups. The right sides of each carcass were placed in a -10 to 1°C chilling cooler (fast chilling) immediately following the slaughter. Left sides from each carcass were placed in a 149 to 16°C chilling cooler (slow chilling). After 2# hr both sides were moved to a O0 to 2° cooler for the remainder of a 8 days storage period. At 2 and 8 days postmortem longissimus muscle samples were removed from the lumbar region for panel tenderness, Warner—Bratzler shear, sarcomere length, myofibrillar fragmentation, collagen, moisture and ether extract determinations. At 48 hr and 8 days postmortem, steaks from slow chilled carcasses of cows, Holstein steers, bullocks and beef-type steers were more tender than those chilled rapidly. However, the differences in chilling rate from the fat group of cows, bullocks and Holstein steers were not sig- nificant. The tenderness of steaks between fat and thin carcasses under the same chilling treatment showed a tendency for fat carcasses to be more tender than those from thin carcasses. This tendency was significant (P‘< .05), except for the cows, Holstein steers and bullocks chilled slowly and beef—type steers chilled at either rate. All steaks at 8 days postmortem were more tender than 2 days steaks. However, only fat cows, thin Holstein steers and thin bullocks were significant. The sarcomere lengths of myofibrils from slowly chilled carcasses were greater than those from rapidly chilled carcasses. After 8 days postmortem aging, sarcomeres were shorter than those at 2 days. Irrespec- tive of chilling rate and degree of fatness, sarcomere length was not significantly different in any of the treatments studied. Sarcomere length was not significantly correlated with tenderness. Myofibrils of longissimus muscles from slow chilled carcasses had more fragments than those from fast chilled carcasses. Significant diff- erences were observed between the carcasses at 2 days and 8 days post- mortem. Chilling treatment appeared to have a greater effect on myofi- bril fragmentation in beef-type steers than did postmortem aging. How- ever, none of these differences was significant (P-< .05). Fragmentation was highly correlated with tenderness (P‘< .01). Quantity of intramuscular collagen did not contribute significantly to meat tenderness. Moisture content was negatively correlated with panel tenderness (P‘< .05) but was not correlated with Warner-Bratzler shear value. Moisture content was highly associated with ether extract (P‘< .01). Degree of marbling and 12th rib fat thickness were not significantly correlated with tenderness. THE EFFECT OF FATNESS, CHILLING RATE AND SEX GROUP ON QUALITATIVE PROPERTIES OF‘BOVINE CARCASSES By Hsiang Chia Lee A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Animal Husbandry 1976 ACKNOWLEDGEMENT The author wishes to express sincere appreciation and thanks to his major professor, Dr. R. A. Merkel, for his guidance and support throughout this study and for his help in preparing this manuscript. Appreciation is also expressed to Dr. A. M. Pearson and Dr. W. G. Bergen for serving as members of the guidance committee. Special thanks are extended to Dr. W. T. Magee and Dr. J. L. Gill for their assistance with the statistical analysis and to Mrs. C. M. Yang for computing all the data. The author is grateful to Mrs. Dora Spooner for her assistance throughout this study and to Mr. J. R. Anstead fOr slaughtering all cattle used in this study. The author is appreciative of the guidance and discussions with all the members in the Meat Laboratory. The author is indebted to his wife, Jane, for her understanding, encouragement and typing of this manuscript. Lastly, the author expresses his appreciation to his parents, Mr. and Mrs. S. E. Lee, fer their continued support throughout his educational pursuits. ii TABLE OF CONTENTS PAGE INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . 1 LITERATURE REVIEW . . . . . . . . . . . . . . . . . . . . . . . 3 Post Mertem Change in Meat . . . . . . . . . . . . . . . 3 Chemical Changes . . . . . . . . . . . . . . . . . . . 3 Physical Changes . . . . . . . . . . . . . . . . . . . 5 Cold Shortening . . . . . . . . . . . . . . . . . . . 9 Thaw Rigor . . . . . . . . . . . . . . . . . . . . . . 11 Factors Affecting Tenderness . . . . . . . . . . . . . . . 13 Shortening Effect . . . . . . . . . . . . . . . . . . 13 Aging Effect . . . . . . . . . . . . . . . . . . . . . 14 Connective Tissue Effect . . . . . . . . . . . . . . . 16 Sex Effect . . . . . . . . . . . . . . . . . . . . . . 18 Fatness Effect . . . . . . . . . . . . . . . . . . . . 19 Ultimate pH . . . . . . . . . . . . . . . . . . . . . 20 Electrical Stimulation . . . . . . . . . . . . . . . . 21 MATERIALS AND METHODS. . . . . . . . . . . . . . . . . . . . . . 23 Experimental Animals . . . . . . . . . . . . . . . . . . . 23 Slaughter Procedure . . . . . . . . . . . . . . . . . . . . 24 Measurement of pH and Temperature . . . . . . . . . . . . . 24 Measurement of Body Composition . . . . . . . . . . . . . . 25 Fat Thickness . . . . . . . . . . . . . . . . . . . . 25 Marbling . . . . . . . . . . . . . . . . . . . . . . . 25 Cutting and Sampling Procedure . . . . . . . . . . . . . . 25 Measurement of Muscle Composition . . . . . . . . . . . . . 27 Moisture-Oven drying . . . . . . . . . . . . . . . . . 27 Ether Extraction . . . . . . . . . . . . . . . . . . . 27 Connective Tissue . . . . . . . . . . . . . . . . . . 27 Cooking Method . . . . . . . . . . . . . . . . . . . . . . 28 Measurement of Tenderness . . . . . . . . . . . . . . . . . 29 iii Measurement of Sarcomere Length . Fragmentation Determination . . Homogenization for Fragmentation . Measurement of Turbidity . . Kjeldahl Protein Analysis Statistical Analysis RESULTS AND DISCUSSION . . . . . . . Postmortem Temperature Changes . Postmortem pH Changes . . . . . . Panel Tenderness Warner-Bratzler shear . . . . . Sarcomere Length . . . . . . Fragmentation . . . . . . . . . Intramuscular Collagen . . . . . . Moisture, Marbling and Ether Extract SUMMARY . . . . . . . . . . . . . . . LITERATURE CITED . . . . . . . . . . . . APPENDIX . . . . . . . . . . . . . . . iv PAGE 29 3O 3O 30 31 33 34 34 36 47 50 56 60 61 64 74 77 90 TABLE 10 11 12 13 14 15 16 17 18 LIST OF TABLES Distribution of carcasses within sex and fat thickness groups C O O O O O O I O I O C I O O O O O O O O C O O 0 Means of panel tenderness of cows and Holstein steers . . Means of panel tenderness of bullocks and beef—type steers PAGE 23 48 49 Simple correlation coefficients between various palatability traits, physical and chemical analysis of pooled cows, Holstein steers and bullocks . . . . . . . . . . . . . . . . . . . 51 Simple correlation coefficients between various palatability traits, physical and chemical analysis of beef-type steers Means of Warner-Bratzler shear of cows and Holstein steers Means of Warner-Bratzler shear of bullocks and beef-type Steers I O O O O O O O O O O O O O O O O O O O O O I O O 0 Means of sarcomere length of cows and Holstein steers . . Means of sarcomere length of bullocks and beef-type steers Means of fragmentation of cows and Holstein steers . . . Means of fragmentation of bullocks and beef-type steers . Means of percentage intramuscular collagen of cows and Holstein steers . . . . . . . . . . . . . . . . . . . Means of percentage intramuscular collagen of bullocks and beef-type steers . . . . . . . . . . . . . . . . . Means of moisture of cows and Holstein steers . . . . . Means of moisture of bullocks and beef—type steers . . . . Means of ether extract of cows and Holstein steers . . . . Means of ether extract of bullocks and beef-type steers . Marbling scores . . . . . . . . . . . . . . . . . . . . . 52 53 54 58 59 62 63 65 66 69 70 71 72 73 LIST OF FIGURES FIGURE PAGE 1 Standard curve for adjusting myofibril fragmentation measurements . . . . . . . . . . . . . . . . . . . . . . . 32 2 Rate of temperature decline in beef-type steers . . . . . 35 3 Rate of pH decline in fat cows muscles with fast and slow chilling . . . . . . . . . . . . . . . . . . . . . . . . . 37 4 Rate of pH decline in thin cows muscles with fast and slow Chilling O I I O O O O O O O O O O O O O O O C I O O O I O 38 5 Rate of pH decline in fat Holstein steers muscles with fast and slow chilling . . . . . . . . . . . . . . . . . . 39 6 Rate of pH decline in thin Holstein steers muscles with fast and slow chilling . . . . . . . . . . . . . . . . . . 40 7 Rate of pH decline in fat bullocks muscles with fast and slow chilling . . . . . . . . . . . . . . . . . . . . . . 41 8 Rate of pH decline in thin bullocks muscles with fast and slow chilling . . . . . . . . . . . . . . . . . . . . . . 42 9 Rate of pH decline in fat beef-type steers muscles with fast and slow chilling . . . . . . . . . . . . . . . . . . 43 10 Rate of pH decline in thin beef-type steers muscles with fast and slow chilling . . . . . . . . . . . . . . . . . . 44 vi LIST OF APPENDIX TABLES APPENDIX PAGE I Raw data of temperature (QC) decline in fat beef-type steers at various postmortem hours . . . . . . . . . . . 90 II Raw data of temperature (00) decline in thin beef-type steers at various postmortem hours . . . . . . . . . . . 91 III Raw data of pH decline in cows at various postmortem hours I I I I I I I I I I I I I I I I I I I I I I I I I 92 IV Raw data of pH decline in bullocks at various POStmorI/em hours I I I I I I I I I I I I I I I I I I I I 93 V Raw data of pH decline in Holstein steers at various postmortem hours . . . . . . . . . . . . . . . . . . . . 94 VI Raw data of pH decline in beef-type steers at various Postmortem hours I I I I I I I I I I I I I I I I I I I I 95 VII Raw data of chemical and physical traits. A 1. Identification of variable number . . . . . . . . . . . 97 vii INTRODUCTION Refrigeration is the most widely used method of meat preservation. Fast and early refrigeration can reduce or limit microbial proliferation and enzyme and chemical reactions that cause deterioration and spoilage, lower the extent of moisture loss or shrink that results in a dry, shriveled, dark and unattractive surface and permits speedier and hence more economical processing. There is little doubt, however, that the rapid chilling treatments for beef, pork, lamb and veal probably cause some toughening as a consequence and shortening among beef and lamb carcasses, particularly. This is rec0gnized as cold shortening. Cold shortening was first observed by Locker and Hagyard (1963). They observed that excised and unrestrained beef muscle shortened more rapidly at 0°C than at any other temperature and the minimum shortening occurred at 14°C to 19°C. The shortening occurred while about 40% of the ATP still remained and the sarcoplasmic reticulum failed in retaining the Ca2+ ions and the Ca2+ ions are released from the sarcoplasmic reticulum. In the presence of Ca2+, the inhibitory effect that the regulatory complex (troponin and tropomyosin) has to prevent actin from activating the myosin ATPase is removed when calcium is bound to troponin. ATP is then split, actin combines with myosin and muscle contraction occurs. Cold shortening will decrease the tenderness and shorten the length of muscle. The Harner-Bratzler shear, taste panels, sarcomere length measurement were used in this research to determine the extent 1 of cold shortening and rigor resOlution. Fat is a relatively good insulator, and is capable of significantly retarding the rate of heat transfer from a carcass. The primary purpose of this research was to investigate whether subcutaneous and intra- muscular fat effects the tenderness of muscles by insulating the muscle fibers during postmortem chilling, as well as, the rate of temperature changes and pH reductions and their influence on cold shortening. Postmortem aging of meat, sometimes called conditioning, ripening, or hanging, is a common practice in meat merchandising to improve the tenderness of beef. The second purpose of this research was to deter- mine whether aging will nullify the effect of cold shortening. The third purpose of this research was to study the different effects of cold shortening on bullocks, steers and cows. Hestetler §t_§l. (1975) reported that muscle samples from bullock and steer carcasses did not differ in sarcomere length, and gave similar response in shortening during onset of rigor. However, muscles from steer carcasses were significantly more tender than those from bullock carcasses. A fourth purpose of this study was to elucidate whether connective tissue, ether extract and moisture content will affect the extent of cold shortening. Since most work with connective tissue has been concerned with tenderness, little information is available concerning chemical components related to the effect of cold shortening. LITERATURE REVIEW Postmortem Changes in Meat The death of an animal does not signal the death of its musculature. Many of the reactions and responses characteristic of the living material are able to continue relatively undiminished into the postmortem phase except as limited by the inability of the tissue to synthesis or to remove certain metabolites. Chemical Changes. The chemistry of postmortem changes in muscle is essentially anaerobic glycolysis. This is the conversion of glycogen to lactic acid and can be easily estimated by following pH decline (Bate-Smith and Bendall, 1949, 1956; Bendall, 1960 and Cassens, 1966). When adequate glycogen is present, postmortem glycolysis in mammalian muscle frequently results in the pH falling to an ultimate value of 5.4 to 5.5. However, in some muscles the ultimate pH is appreciably higher than this (lawrie, 1955; Howard and Iawrie, 1957; Lawrie stain 1959). Excessively low values (below 5.1) have also been noted by Iawrie §t_§l, (1958) in pig muscle. Bate-Smith and Bendall (1949) noted that an ultimate pH value of 5.3 appeared to be a limiting value, below which glycolysis was completely inhibited. They considered that the most probable explanation for this was that one or other of the enzymes involved in glycolysis was increasingly inhibited as the pH fell. Glycolysis ceased in some muscles at appreciably higher values. Briskey and lawrie (1961) suggested that in these muscles either the phosphorylase was inactivated more readily or the glycogen is less accessible to attack. The rate of pH fall postmortem varies considerably in certain skeletal muscles (ludvigsen, 1954; Wismer-Pedersen, 1959; Briskey and Wismer-Pedersen, 1961; McLoughlin, 1963; Elliot, 1965). The rate of pH and ATP change is significantly influenced by the muscle temperature (Bate—Smith and Bendall. 1949; Bendall, 1951; Marsh, 1954; Marsh and Thompson, 1958; Bendall, 1960; de Fremery and Pool, 1960; Cook and Langsworth, 1966; Cassens and Newbold, 1967). But the effect of tem- perature is not the same with all muscles and temperature will have very little influence upon the ultimate muscle pH. The greatest drop in pH and loss of ATP occurs during the first 2 to 3 hr postmortem (Kastner et. a1... 1973). Cassens and Newbold (1967) found that in the range 5°C to 37°C the pH of the ox stggngmandigglaris (neck) muscle fell more slowly at lower temperatures and there was a period of several hours during which the pH of muscle stored at 1°C fell faster than that of muscle at 5°C. The ultimate pH attained at 1°C or 5°C was significantly higher than that attained at 15°, 25° or 37°C. With rabbit p§9§§_muscle, Bendall (1960) reported that the lower the tem- perature in the range 0°C to 37°C the more slowly the pH fall. The extent of the pH fall may depend on the amount of glchgen present in the muscle at the time of slaughter. The glycogen content can be re- duced by starvation, exhausting exercise, the imposition of pre-slaughter stresses of various sorts, or by struggling at the time of slaughter (Lawrie, 1966). It can be reduced by the pre-slaughter injection of insulin (Bate-Smith and Bendall, 1947, 1949; Howard and Lawrie, 1956, 1957) or adrenalin (Radoucco-Thomas §t_al,, 1959 de Fremery and Pool, 1963; Klose §t_§1,, 1970; Khan and Nakamura, 1970; Bouton gt al,, 1971). Struggling at death will accelerate the rate of postmortem glycolysis because under such conditions phosphocreatine is depleted and the resynthesis of ATP is primarily dependent on the anaerobic breakdown of glyc0gen (Bendall, 1960). The release of adrenalin at death will contribute a postmortem biochemical environment conducive to an increased rate of anaerobic glycolysis (Cori, 1956). Adrenalin converts the inactive (8) form of phosphorylase to the active ((1) form. McIoughlin (1970) found that anoxia just before or at death and the release of adrenalin probably contributed appreciably less to the effect of the death reaction than did muscular contraction. Muscle contraction at death appreciably influenced the course of postmortem glycolysis. Bodwell g1; al- (1965) reported that the average initial pH value of 6.99 declined to 5.46 at 48 hr and was 5.57 at 480 hours. Glycogen appeared to be stoichiometrically degraded to lactic acid and reducing sugars. The sum of these constituents was approximately constant at all times postmortem, if expressed in terms of glucose equivalents. sic C es At the time of slaughter, muscle is plastic and highly extensible; from the time of death muscle plasma goes through a series of characteristic changes. This is rigor mortis, a condition of rigidity or contracture which deve10ps in a matter of hours after death (Wierbicki £1; a}... 1954). In full rigor it is firm and relatively inextensible. In addition to losing its extensibility, unrestrained muscle shortens during the deve10pment of rigor mortis. Various studies have established that postmortem shortening occurs by a sliding of the thick and thin filaments such as occurs during physiOIOgical contraction (Bendall, 1951; Stromer §t_§l., 1967; Stromer and G011, 1967) and that this shortening is the primary cause of carcass stiffening during the development of rigor (Okubanjo and Stouffer, 1975). Huxley (1964) found that during muscular contraction the interdigitation of myosin with actin filaments drew the Z-band together reducing the sarcomere length and increasing the cross-seetional area in inverse prOportion. Buck and Black (1967) studied seven pairs of muscle strips prepared from bovine loggissimus muscle in two degrees of stretch-tension during rigor and indicated that the average muscle fiber diameter was significantly smaller in stretched muscle strips. Onset of rigor mortis is defined as the period of increasing isometric tension deve10pment (Busch, 1967; Goll, 1968; Goll 949-91., 1970, 1971; Jungk gt a1” 1967). Attempted shortening (;,§,, isometric tension development) by muscles on opposing sides of the same bone would cause carcass stiffness or rigidity. These physical changes have been quantified during normal rigor deve10pment through the measurement of the isometric tension developed by Jungk 23 a1. (1967), Schmidt g1; al- (1968), Chrystall pp al- (1970) and Busch gt al.- (1972). The coincidence between the onset of rigor mortis an appreciable increase in the modulus of elasticity was reported by Bate-Smith (1939) who noted that new crossbonds were formed between the muscle contractile units following the loss of ATP. The duration of the rigor process depends on three things 3 the initial level of ATP, the initial glycogen reserve, and the initial reserve of phosphocreatine which acts as an important source of resyn- thesis of ATP (lohmann, 1935; Bendall, 1951). Newbold and Harris (1972) reported that shortening could occur only while ATP was present. When all the ATP was lost the rigor process was complete, and the muscle was ' fixed in whatever state of contraction it happened to be at the time. Kushmerick and Davies (1968) as well as Schmidt and Briskey (1968) have also shown that an appreciable degradation of both ATP and ADP is essential for the development of muscle inextensibility. Conversely, postmortem shortening requires ATP as an energy source. Goll gt _a_._l__. (1970) have stated that the reason rigor mortis does not occur until just before the complete loss of ATP is that the decline in ATP concentration lowers the ability of the sarcoplasmic reticulum to accumulate calcium ions against a concentration gradient, and this release of calcium ions is required to initiate tension development. Busch §t_al. (1967) and Jungk gt al. (1967) reported separately that after a given period of postmortem storage both rabbit and bovine muscle strips gradually develOped tension when suspended isometrically. Jungk et al, (1967) found that the time at which isometric tension deve10pment began depended on environmental temperature of the strips and on antemortem condition of the animal. Exhausted muscle containing little or no glyCOgen will pass more quickly into rigor than rested muscles. Rapid loss of extension has been reported to begin when the ATP level has fallen to about 30% of its initial level in horse muscle by Lawrie (1953) and in chicken muscle by de Fremery and Pool (1960), to about 25% and 50% in rabbit muscle at 17°C and 37°C, respectively, by Bendall and Davey (1957) and to about 67% in beef muscle by Howard and Lawrie (1957). Two different values 87% (lawrie, 1960) and 30% (Bendall g1; gl_., 1963) have been reported for pig muscle. Busch (1972) reported that tension deve10pment in rabbit and porcine longissimus muscle was minimal and similar at 2°, 160 and 25°C but increased greatly if the strips were incubated at 37°C. Bovine semitgndinosus muscle strips deve10ped most isometric tension when stored at 2°C, and least isometric tension at 160 to 25°C. Isometric tension development in bovine muscle, like rabbit and porcine muscle, reached a maximum sooner after death at 370C than it does at 2°, 160 or 25°C. Maximum isometric tension was usually attained within 3 to 16 hr after death. After maximum isometric tension had been reached, ability of the muscle strip to maintain this tension deve10pment in the absence of ATP gradually declined and isometric tension therefore also gradually de- clined. Decline of postmortem isometric tension occurred more slowly than isometric tension development, and 24 to 48 hr of postmortem storage were required for a 50% to 80% decline in isometric tension. Loss of ability to maintain this tension deve10pment would result in dissipation of rigidity, or in carcass softening.‘ The period of isometric tension decline is defined as resolution of rigor mortis (Busch 2:91;” 1967; Coll, 1968; Goll ggglw 1970, 1971; Jungk gpgl_., 1967). Busch 531; §._]_._. (1967) and Jungk gt 2.1. (1967) stated that postmortem isometric tension decline was most noticeable at environmental temperatures under 16°C and decline of isometric tension might not occur at environmental temperatures near 37°C. Busch gt g1, (1972) further examined the postmortem changes in isometric tension and reported that decline of isometric tension was most rapid at 37°C and is somewhat slower at 2°C or 16°C. Bovine muscle strips lost all isometric tension after 30 hr at 37°C and rabbit pgggg muscle usually lost all its isometric tension after 12 to 24 hr at 37°C. Cold Shortenigg, The shortening of excised muscle during onset of rigor increased with storage temperature from 17°C to 37°C was reported by Bendall (1951) with rabbit muscle and by Marsh (1954) with beef. However, Locker and Hagyard (1963) investigated excised unrestrained beef muscle which was stored at 0°C and found that while undergoing rigor mortis it displayed more rapid shortening than at any other temperature and observed that muscle stored at 14°C to 19°C had minimal shortening. The length change of ox neck muscle placed at 0°C to 200 within 2 or 3 hr postmortem, usually exceeded 50% and might attain 60% of the initial excised length. This phenomena is known as cold shortening. Cold shortening not only occurred in beef sternomandibularis muscle, but also was feund to occur for beef loggissimus muscle and to a lesser extent for beef p§9g§_mgjg;_muscle. Ovine (Cook and Langsworth, 1966; Marsh, 1968), porcine (Galloway and 0011, 1967; Henderson g§_gl., 1970; Hendricks gt 21.. 1971), rabbit red semitendinosus (Henderson gt_gl., 1970) and avian (Smith gp_gl,, 1969) muscle have also been shown to cold shorten. 10 Locker and Hagyard (1963) also pointed out that cold shortening could not be provoked at all in the white muscles of the rabbit. Jungk and Marion (1970) detected no cold shortening in turkey pegtoralis held at 4°C, but Smith gt_. _a__.l_. (1969) reported that excised pectoralis pgjgr muscles of chicken and turkey shortened significantly more at 0°C than 12°C to 18°C. Newbold (1966) reviewed the chemical changes involved in cold shortening and indicated that shortening occurred while about 40% of the ATP still remained. This demonstrated the observations of Marsh and Thompson (1958), Locker and Hagyard (1963) and Marsh and Leet (1966) that cold shortening decreases as the period between slaughter and exposure to cold or freezing conditions is extended. With phase microscOpy, Stromer gt_alp (1967) feund that the 16°C- 24 hour samples exhibited a marked thickening of the A—band, a shor- tening of the I-band, and a replacement of the H-zone by a dark line or band. The 2°C—24 hour samples showed only alternating light and dark bands of nearly equal width, which were described as a supercon- tracted pattern. In the same year, Stromer gt g1. (1967) studied the myofibril with an electron microsc0pe and found that myofibrils from muscle sampled 24 hr postmortem at 2°C were supercontracted with thick filaments pushed against or through the Z-line, and no trace of I-bands remained. Myofibrils from muscle sampled 24 hr postmortem at 16°C were contracted, but to a much lesser extent than 2°C-24 hour myofibrils. Voyle (1969) studied the histology of beef neck muscle shortened 11 at 20C using the light and electron micrOSCOpes. He found that less than half the fibers had actively shortened with a mean sarcomere length of 1.1 micrometers. The others were crimped, although these also had shortened substantially (mean, 1.6.xm). A control, allowed to go into rigor at 18°C restrained only by its own suspended weight, had only straight fibers (mean, 2.34am). Individual fibers among those actively shortened contained both contraction nodes and stretched areas as well as breaks. Thaw Rigor. Thaw rigor or sometimes called thaw shortening was first observed by Moran (1930) in frog muscle in a strip of pre—rigor muscle which was frozen fairly rapidly and thawed at a later time. Extensive shortening took place within quite a short period which was accompanied by copious " drip ". Marsh and Thompson (1958) studied thaw rigor in lamb, using excised loggisgimgs muscle and found that if lamb was frozen immediately and thawed at 16°C to 20°C, there was an average shortening of 72%, with a 27%.loss in weight as drip. Muscle frozen in rigor and then thawed, shortened by only 5% with 3% drip. If muscle was frozen pre-rigor, the drip increased with ambient thawing temperature, rising rapidly between 5°C and 10°C. Muscle thawed at -3.5°C for four days did not shorten or have any appreciable drip losses. Bendall (1960) noted that considerable thaw rigor occurred in rabbit muscle before the ATP level had fallen significantly and that after shortening had proceeded rapidly for a few minutes there was a 12 temporary increase in length of loaded strips followed by further relatively slow shortening. Newbold (1966) showed that the rapid and drastic physical events of thaw rigor precede the accelerated metabolic run down. The onset of thaw rigor occurred while the amount of ATP was relatively high (40%). The pH fall and disappearance of ATP were almost complete within an hour. Okubanjo gp,g;, (1975) reported that the development of thaw tension occurred at all thawing temperatures before the decrease in level of ATP. When thaw rigor occurred, the ability of the sarCOplasmic reticulum to accumulate Ca2+ ions was destroyed so that Ca2+ ions were released in the presence of ATP and muscle contraction had occurred. Thaw shortening in excess of 70% has been reported in rabbit p§2g§_ muscle by Lawrie (1968), ox neck muscle by Marsh and Leet (1966), ScOpes and Newbold (1968) and sheep loggissimus muscle by Marsh and Thompson (1958). Marsh and Thompson (1958) stated that thaw shortening in muscle frozen pre-rigor could be prevented by keeping the muscle at a temperature just below its freezing point for several days before allowing it to thaw. Under these conditions the chemical changes associated with the deve10p- ment of rigor mortis were completed while there was sufficient ice in the muscle to prevent shortening. 13 Factors Affecting Tenderness Tenderness is one of the most important palatability factors in the acceptance of beef and meat from other species. The tenderness of meat is notoriously variable. It varies not only among anatomically different muscles but also among corresponding muscles from animals of the same or different species. Factors that influence tenderness were roughly divided into three time-based groups by Marsh (1972): those which are determined before the birth of the animal (gpg, breed, sex), those modified by management during life (age, acidity, fat content, feed), and those affected by treatment before and after the musculature set in rigor mortis (hot boning, suspension methods, chilling rate, aging, cooking method, etc.). This review lists some of these factors and their relationships to tenderness. ShortenigggEffect. In 1960, Locker concluded that there was a relationship between postmortem shortening and tenderness. Recently, McCrae gt_gl, (1971) observed that the same relationship fer lamb muscles as that previously found for ox neck muscle. Pre-rigor excised breast muscle from chicken was considerably tougher than muscle that was left attached to the skeleton as reported by Lowe and Stewart (1946). Ramsbottom and Strandine (1949) removed the loggissimus muscle from beef carcasses before chill and reported that these samples were considerably less tender than paired non— excised muscles. Locker and Hagyard (1963) reported that the stimuli of l4 excision caused a small quantity of the contraction ultimately obtained. Using ox muscles excised soon after slaughter, Marsh and Leet (1966) and Davey gg gl. (1967) showed that shortening up to 20% of the excised length produced relatively small changes in tenderness, whereas further shortening.from 20% to 40% produced a several-fold increase in shear value. With further shortening there was a progressive decrease in toughness until at 60% shortening shear values were of the same order as those obtained at 20% shortening or less. Herring gg gl_. (1967) and Davey g§_gl, (1967) reported that stretching muscle and allowing it to go into rigor in this condition had little effect on tenderness. Utilizing isometric tension measurements, Jungk gt_gl, (1967) suggested that the increase and decrease in tension postmortem, probably corresponded to similar phases of decreasing and increasing tenderness. However, Busch gt_gl. (1967) reported that isometric tension measurements are not necessarily a valid method for determination of shear values. They concluded that shortening contributed to muscle tenderness, but probably was not the main contributor. Agigg Effect, Aging of carcass beef at refrigeration temperature for several days is regarded as a necessary procedure to obtain retail beef of satisfactory tenderness. Although research reports on aging effects appeared about 70 years ago (Lehmann, 1907), reasons that cause meat tenderness is still not well understood. Stanley gt_al. (1974) suggested that at least four separate me- chanisms might be at work during postmortem aging-specific chemical 15 changes at the Z-line and perhaps actin-myosin interaction site, catheptic activity, degradation of collagen cross-links and general microbial action. Davey g g. (1967) demonstrated that when the amount of shortening of ox neck muscle increased above 20% the tenderness improvement with aging became smaller. At 40% shortening or greater there was no improvement. However, Herring g§_al, (1967), using ox ggmitgpgip9§g§_ muscle, showed that during aging, muscle which had shortened to a sarcomere length of about 1.5 pm improved in tenderness. Busch gp,gl, (1967) and Sleeth gt al, (1957, 1958) reported ac- celerated tenderization with high aging temperatures. Henderson.gp,a;, (1970) found that Z-line degradation occurred more rapidly upon storage at 25°C or 37°C xgp§p§_storage at 2°C or 16°C. Goll gg gr. (1970), Hay gg gl. (1973) evaluated muscle with trans- mission electron microsc0py and pointed out that postmortem tenderization might be associated with ultrastructural changes in myofibrils including degradation of the Z-line and changes in the actin-myosin interaction. Hegarty 93 gl. (1973) reported structural deterioration in myofibrils from "normally" aged and rigor - stretched turkey and porcine muscle. Z-lines were diffuse and sometimes separated into clumps of Z-line material in samples examined 6 to 9 hr postmortem. Deterioration was more extreme after 24 hr aging and structural changes were more rapid in turkey than in porcine muscle. The tendency for myofibrils to fragment when mechanical stress is applied has been used to evaluate structural deterioration during aging. l6 Fragmentation may result from weakening of bonds between the actin filaments and the Z—line material (Johnson and Bowers, 1976). Dutson and Lawrie (1974) studied the effect of postmortem aging on bovine muscle tenderness and observed that as time postmortem increased, the protein content of the supernatant from homogenized muscle tissue increased and the muscle became more tender. Moller gp_gl. (1973) found a correlation coefficient of .78 between the light absorbance of a myofibril suspension and beef tenderness at 7 days postmortem. Stanley (1974) studied the effect of aging on beef pgggg and semitendinosus muscle by scanning electron micros00py and found that myofibrils immediately postmortem were unbroken and crossed by continuous transverse elements at the level of the Z-line. At six days postmortem, breaks were beginning to be seen in myofibrils and transverse elements were less pronounced. At 12 days postmortem these trends had intensified and a general deterioration in structure might be seen. Eino and- Stanley (1973) and Stanley and Eino (1974) found that catheptic activity reached its maximum activity between 4 and 6 days postmortem. Since sarcomere length decreased up to 2 day postmortem and increased thereafter while tenderness generally increased over the first 2 days, it might be other changes in the myofibril such as weakened actin - myosin interactions or Z-line degradation which caused the differences in tenderness. Connective Tissue Effects, The character and content of connec- tive tissue is one of the major contributors to muscle tenderness. 1? Lesser quantities of connective tissue result in greater tenderness, and consequently the shank muscles are not as tender as loggissimus or pgggg_ggjgg_muscles. Cover gt g1, (1962), Herring gt_gi. (1967) and Field gp_al. (1970) reported that some muscles had more collagen than others and the amount of collagen in various muscles had a negative relationship to tenderness. Goll gg,g;, (1963) McClain gt al, (1965) and Herring gt_al, (1967) showed that as tenderness decreased due to increased animal age there was essentially no change in the total amount of collagen present in the muscle, and that, although tenderness of muscle increased due to postmortem aging, there was little change in the total amount of collagen over the postmortem aging period. However, Goll gg,gl. (1964) and Carmichael and Lawrie (1967) showed that differ- ences in the character of the connective tissue could be observed in older, tougher muscle compared with more youthful, tender muscle. In addition, Coll gg,gl, (1963, 1964), Hill (1966) and Herring gt g1. (1967) also reported that the amount of heat labile or percentage soluble collagen decreased with increase in animal age over a wide range of ages. This decrease was associated with the decreased tenderness of aged animals. Changes in the molecular structure of collagen due to postmortem aging was reported by Kruggel and Field (1971), Pfeiffer.§t_al, (1972) and Stanley and Brown (1973). They found that there was an increase in the amount of smaller molecular weight subunits and a decrease in the amount of larger molecular weight subunits that could be extracted from muscles with increased postmortem aging. Kruggel and Field (1971) and Pfeiffer gt_gl. (1972) indicated that 18 the amount of extractable low molecular weight collagen subunits was increased by stretching a muscle. Pfeiffer gt_gl, (1972), Shimokomaki gp_§l, (1972) and Bailey (1972) reported that tenderness might be affected by the degree of cross-linking in intramuscular connective tissue. Sex Effect. The facts that bulls grow faster than steers or heifers, are leaner, more efficient and have larger loggissimus muscles and that steers are leaner than heifers and cows have been reported by many researchers. locker and Hagyard (1963) reported that muscles from steer carcasses sustained greater shortening than samples from cow carcasses when stored at 19°C and 310C. However, when carcasses were refrigerated at 2°C, the samples from cow carcasses shortened to a greater extent than the muscle sample from steer carcasses. Wierbicki gp,al. (1956) found that at 3 days the untreated steers were more tender than the diethylstilbestrol treated bulls. At 13 days postmortem the differences between heifers, bulls and steers were not significant. Hedrick gp_gl, (1969) showed no significant differences in Warner- Bratzler shear values of steaks from bulls less that 16 months of age and steers and heifers of comparable chronolOgical age. However, shear values of steaks from more mature bulls were greater than those from steers of heifers at the same age. Champagne g g. (1969) and Warwick gg gag. (1970) reported l9 nonsignificant differences in tenderness ratings between steaks from bull and steer carcasses. In contrast, Field gp,gl, (1966), Hedrick gggl. (1969), Arthaud gt_gg. (1970), Hunsley gg a_l_. (1971), Reagan 23.21: (1971) and Hostetler gt_gl, (1975) reported that muscle samples from bull and bullock carcasses were less tender than those from steer and heifer carcasses. When animals were slaughtered at a reasonably young age there is little consumer discrimination against corresponding muscles of any sex group in tenderness. Fatness Effectgr It is generally believed that fatter animals produce meat that is more tender than that from leaner animals. Fatter animals also tend to deposit greater quantities of marbling and the increased deposition of intramuscular fat is associated, although not very highly, with increased palatability of cooked meat. McBee and Wiles (1967) found significant differences in tenderness, juiciness and flavor among carcass grades of Prime, Choice, Good and Standard. Dryden and Marchello (1970) reported a significant correlation between muscle fat content and taste panel tenderness. However, Henrickson and Moore (1965), Walter gg gl_. (1965), Breidenstein gg a_l_. (1968), Norris gt_ a_l_. (1971) and Parrish gg a_l_. (1973) emphasized that tenderness was not significantly affected by marbling over a wide range of marbling scores. Cover gt al, (1956) and Campion and Grouse (1975) found that although correlations between ether extract, marbling and tenderness were positive, none was very high. Field §p_al, (1966) used roasts from the longissimus muscle of bulls, steers and heifers, which contained 20 marbling degrees ranging from traces to moderate, and fOund that warner-Bratzler shear scores were not significantly affected by marbling when age was held constant. Significant correlations were found between marbling and palatability for steers and heifers, but not for bulls. Cross gp_gl, (1972) and Reagan (1974) reported significant (P«< .01) correlations between intramuscular fat content and sarcomere length in lamb and beef loggissimus muscles, respectively, suggesting that marbling might also be related to tenderness via its insulatory effect in reducing the severity of cold shortening induced by low tem- perature chilling. Ultimate pHI Mackey g3_§;, (1952) used pork with a pH range of 5.57 to 6.39 and found no relationship between pH and tenderness. However, Bouton £3.91, (1957) reported a curvilinear relationship be- tween taste panel scores and the ultimate pH of beef muscles (range 5.4 to 6.4) with a maximum toughness at pH 5.9. Penny gt gl. (1963) and de Fremery (1963) induced high ultimate pH by pre-slaughter injection of epidephrine and/or iodoacetate and f0und that meat with a high pH was more tender and juicy than that with a low pH. Miles and Lawrie (1970) reported that shear force values decreased linearly as the pH of rabbit muscles increased from 5.4 to 7.2. Investigating changes in the ability of muscle proteins to retain water and in mechanical properties as the pH of sheep muscle varied from 5.4 to 7.0, Bouton pg _a_._l_. (1971, 1972) considered that although 21 ultimate pH influenced both myofibrillar strength and adhesion between muscle fibers, those measurements reflecting myofibrillar toughness were most affected. Using 20 Hereford steers, Bouton gg_g;. (1973) reported that the taste panel and shear force measurements are linearly and significantly related to pH for both the normal and stretched samples from lo issimus, adductor and pggtg§_femoris muscles and tenderness increased with in- creasing ultimate pH. Electrical Stimulation, Electrical stimulation was first used to accelerate aging of beef by Harsham and Deatherage (1951). They observed that stimulation of beef carcasses at 3000 volts produced a fall in the pH of muscle to 6.1 in 1 hour. The meat was as tender after 2 days at 1°C as that from unstimulated controls after 18 days at 1°C. de Fremery and Pool (1960) found that electrical stimulation of chicken breast muscle for 15 min increased the initial rates of fall in pH and ATP content. Hallund and Bendall (1965), Forrest and Briskey (1967), McLaughlin (1970) and Tarrant gp_gl. (1972) reported that, in pigs with a naturally slow glycolytic rate, 30 sec of stimulation approximately doubled the rate of pH fall. Carse (1973), Chrystall and Hagyard (1976) reported that glycolysis of freshly slaughtered lambs was accelerated by the high voltage (3600 V) electrical stimulation. Loggissimus muscle pH in stimulated carcasses fell to below 6 within 1 hr of slaughter, compared with the 14 hr 22 required by unstimulated muscle. Shear force values for muscles from leg and loin cuts of stimulated carcasses roasted from the frozen state were about half of those from unstimulated carcasses and there were no deleterious effects due to stimulation. Davey, Gilbert and Carse (1975) stimulated beef sides for a 1 to 2 min period with high-voltage ( 3600 v) electric stimulation immediately after carcass dressing and found that the time for rigor deve10pment was reduced from 24 hr to about 5 hours. The stimulated carcasses even though chilled rapidly were still warm at rigor entry. Cold shortening and toughening would not develop under these conditions and the meat could be aged to a high degree of uniform tenderness. MATERIALS AND METHODS Experimental Animals This study was divided into two separate experiments. Experiment 1 consisted of a study to observe the effect of cold-shortening on bovine muscle and its relationship to sex, fatness, postmortem aging and rate of postmortem pH decline. Ten cows, ten bullocks and ten Holstein steers were used in the first experiment of this study. Each group of cattle was equally divided into two fatness ranges according to fat thickness at their 12th rib and this breakdown is shown in table 1. TABLE 1. DISTRIBUTION OF CARCASSES WITHIN SEX AND FAT THICKNESS GROUPS Fat thickness (12th rib) a Experiment Sex Fat group Thin group 1 b Cows .91 (.76 - 1.27) .18 (.01 - .25) Hgizzgin .69 (.32 - 1.02) .18 (.13 - .25) Bullocks .48 (.41 - .51) .18 (.01 - .38) 2 ° BgifigigPe 1.65 (.89 - 2.16) .47 (.25 - .64) aFat thickness in centimeters measured 3/4 lateral length of loggiggimug muscle. bFi ve carcasses per group. c Ten carcasses per group. 23 24 Experiment 2 emphasized the effect of cold shortening of beef-type steers with wide differences in fatness. Twenty steers were used in the second experiment of this study and divided into two fatness ranges according to their 12th rib fat thickness (table 1). Slaughter Procedures All cattle were slaughtered at the Michigan State University Meat Science Laboratory. They were fasted approximately 17 hr prior to slaughter. Two cattle were slaughtered each slaughter day. The cattle were stunned with a captive bolt pistol, exsanguinated and dressed within 60 min following death. All carcasses were split into right and left side and the right side of each carcass was placed in a -1°C to 1°C chilling-cooler. The left side was placed in a 1490 to 16°C cooler. After 24 hr, both sides were moved to a 0°C to 2°C holding cooler for the remainder of the eight day storage period. Measurement of pH and Temperature Internal temperature and pH of the loggissimu§ muscle were monitored during chilling by inserting a thermocouple and a Type 7GR231/100L combination electrode, with a Type 36101 portable pH meter (Kerotest Manafacturing Corp., Pittsburg, Pennsylvania), respectively into the muscle at a point opposite the sixth lumbar vertebra of each side. Temperature and pH measurements were taken on both sides 25 before the carcasses were moved into the respective chilling coolers, at one, two, three, feur, six, eight, 12 and 24 hours. In addition, readings were taken after 48 hr and 8 days postmortem. Measurement of Body Composition Fat ThicknessI The carcasses were ribbed 48 hr postmortem and single fat thickness measurement of subcutaneous fat was made at the twelfth rib. The measurement was made perpendicular to the outer fat surface at a point 3/4 the lateral length of the loggissimus muscle from the vertical process of the twelfth thoracic vertebra (American Meat Science Association, 1967) on the exposed twelfth rib surface of the forequarter. MarbliggI Intramuscular fat was scored in the exposed loggissimus muscle at the twelfth rib based on the standard photOgraphs of the Official United States Department of Agriculture Standards for Grades of Carcass Beef (USDA, 1973). Cutting and Sampling Procedure In experiment 1, the whole shortloin (13th thoracic through the sixth lumbar vertebra) was removed from each side of the carcass at 48 hr postmortem. One 3.8 cm steak was obtained from the 13th thoracic and first lumbar vertebrae region of each shortloin for moisture, ether 26 extract, connective tissue, sarcomere length and fragmentation deter— minations. In addition, two 3.2 cm steaks were removed from the first to third lumbar region for taste panel and Warner-Bratzler shear deter- minations. The remainder of the shortloin was wrapped in parchment paper and stored at 000 to 2°C for an additional six days. After 8 days storage, one 2.5 cm steak was removed from the third lumbar vertebra region of the shortloin and discarded to avoid dessication and any microbial contamination. Then one 3.8 cm and two 3.2 cm steaks were removed from the fourth and fifth lumbar vertebra region of the short- loin for the same determinations as those previously described for the 48 hr samples. In experiment 2, the same procedure for remoVing steaks from the shortloin was followed, except one 1.6 cm steak was removed for shelf life study posterior to where the first three steaks were taken at 48 hr postmortem and again following the removal of steaks after the 8 days storage period. A 2.5Lt cm diameter core was taken from the center of the 3.8 cm thick steak frozen stored at -30°C for sarcomere length and fragmen- tation study. The remaining portion of each of these steaks was ground (Model T215GA, Hobart MFG. Co., Troy, Ohio) twice with a coarse plate (3.0 mm) and twice with a fine plate (1.5 mm). After grinding it was stored in a freezer at -30°C until moisture, ether extraction, and total hydroxyproline determinations could be performed. 27 Measurement of Muscle Composition Moisture - Oven drying. Prior to analysis, the frozen, finely ground samples of the longissimus muscles were thawed in the 0°C cooler fOr 24 hours. After thawing, samples were mixed by stirring with a spatula. A 5 g sample was weighed into a previously dried and weighed aluminum foil moisture dish. The dishes were placed on‘a shelf in an electrically heated oven (Model 18, Precision Scientific Co.) at 100°C. At the end of a 24 hr drying period, the dishes were removed to a desiccator to cool at room temperature, weighed and then kept for ether extraction. The moisture was determined on duplicate samples to insure a difference within .25%. Ether Extraction, The A.0.A.C. (1970) ether extraction method (Goldfisch Method) of the dried sample was used. The dried samples were transfered from the moisture determination dishes to alundum extraction thimbles and placed on ether extraction apparatus and extracted for 4 hr with anhydrous diethyl ether. Duplicate samples were determined and .5% differences were allowed. Connective Tissue. The connective tissue was determined using -the modified procedures of Parrish gg_g;, (1961). The dried, fat free samples were powdered in a mortar and mixed thoroughly. Five hundred mg samples were weighed and placed in ampules containing 5 ml of (distilled water and then 5 ml of 12 N HCl were added. The ampules 28 were sealed and hydrolyzed for 16 to 24 hr at 110°C for hydroxyproline analysis. Standard gelatin samples were also hydrolyzed with each group of meat samples examined. The samples were cooled and neutralized with 24% NaOH, filtered, and diluted to 50 milliliters. Duplicate aliquots of these samples were analyzed for hydroxyline. One-tenth ml of .1 M phosphate buffer pH 7.0 and .1 ml of hydrolyzed sample were pipetted into 10 ml volumetric flasks. Two and one half ml of benzene were added, and the flask was placed in a carrier basket. Two-tenths ml of cold (5°C) .3 M ninhydrin in prersolve (ethylene glycol monomethyl ether) was added and the flasks were transfered to the water bath at 71:10C. The samples were shaken 5 min at 100 strokes per minute and immediately cooled to room temperature in an ice-water bath. The contents of the flasks were diluted to 10 ml with benzene and thoroughly shaken. The organic layer was poured into 20 ml test tubes containing 200 mg of anhydrous sodium sulfate and the mixture was shaken vigorously. The dried solutions were transfered to cuvettes and their absorbancies read in a Spectrophotometer (Model 24, Beckman Instruments Inc. Fullerton, California) at 570 nm and 550 nanometers. The equation derived by Wierbicki and Deatherage (1954) was applied to convert hydroxyproline content to connective tissue content of the samples. Cooking Method Two 3.2 cm thick steaks cut from the loggissimus muscle were cooked for the tenderness determination. A thermometer was inserted 29 into the geometric center of steaks and then cooked in a 138°C deep fat fryer (lard) to an internal temperature of 62°C. The cooked steaks were stored over night at 4°C and used for the panel taste and Warner- Bratzler shear value determinations the following day. Measurement of Tenderness A nineepoint hedonic scale was used by the twelve tasteepanel members consisting of Meat Laboratory faculty, staff and graduate students at Michigan State University to evaluate tenderness of cores (2.5 cm) taken from the steaks. Three 2.5 cm cores were removed from each steak, their browned surfaces removed and each core was cut into two pieces perpendicular to the myofiber axes for tasting. Shear measurements were determined on the same steaks used as those used fOr taste panels. Twelve to 15 - 1.25 cm cores were removed from one steak and shear force (kg) determined with a Warner- Bratzler shear device. Measurement of Sarcomere Length The frozen lopgissimus muscle 2.5 cm core was thawed at 0°C to 490. Approximately 1 g of muscle was placed in 14 ml of .25 M sucrose and blended at low speed in a Virtis homogenizer (Type Super 30 Virtis, New York) for one minute. Sarcomere length was measured by use of a phase-contrast 30 photomicrosc0pe III (Carl Zeiss, Oberkochen, West Germany) equipped with a filar micrometer at a magnification of X2000. The mean length of 10 sarcomeres from each of 25 myofibrils per sample was determined. Fragmentation Determinations Homogenizgtion for Fragmenta_t_i£rg,_ Moller (1973) developed the homogenization procedure for myofibril fragmentation as used in this study. A 2 g sample of the 2.5 cm core of the loggissimus muscle used for sarcomere length was homogenized by a Virtis homogenizer (a blade homogenizer) for 30 sec at medium speed in 12.5 ml KCl-phosphate buffer consistingof .06 M KCl and .05 M potassium phosphate (pH 7.0). The homOgenate was poured through a stainless steel mesh to remove connec- tive tissue and other gross material. The suspension was centrifhged in a Sorvall centrifuge (Model RC 2-B, Sorvall, Inc.) for 3 min at 1800 rpm using a 83-34 rotor. The sediment was washed with three cycles of 12.5 ml KClephosphate buffer solution followed by centrifugation for 30 min at 4000 rpm in the same rotor and centrifuge. Measurement of Turbidity, Partical size of suspended homogenized myofibril fragments was determined essentially as described by Davey and Gilbert (1969). The myofibril sediment was dispersed in 25 ml KCl- :phosphate buffer solution under standard conditions. The suspension solution was stirred for 5 min at 0°C to 4°C using a multiple magnetic 31 stirring apparatus (Lab-Line Instruments, Inc. Melrose Park, Ill.). One ml of homogenized myofibril suspension was pipetted to a cuvette containing approximately .1 mg protein / milliliter. Turbidity readings (colorimeter transmittance units) were made with the Spectronic 20 calorimeter (Bausch and Lomb) at 520 nm immediately after gentle inver- sion of the cuvettes containing the suspensions. The measurements were adjusted to equivalent nitrogen concentration from a standard curve. A linear relationship between turbidity reading and nitrogen concentration was obtained for suspensions containing approximately .08, .10, .15, .20 and .25 mg (figure 1). Total nitrogen concentration of the myofibril suspensions was determined by the Kjeldahl method. Kjglfl Protein Analfiis, The American Instrument Company (1961) Micro-Kjeldahl method was used with modifications. The myofibril suspension was transferred to a Kjeldahl flask with a small amount of distilled water. Glass beads and approximately 1 g of sodium sulfate, 1 ml of 10% copper sulfate, and 7 ml of concentrated sulfuric acid were added to the flask. The mixture was digested over electric coils for 2 to 4 hr with occasional shaking until a light green color deve10ped and then for about 1/2 hr more. The flask and its contents were cooled after digestion and approximately 15 ml of deionized water were added. Nitrogen was distilled into 10 ml of 2% boric acid and three drOps of bromocresol-green indicator solution added to the 125 ml Erlenmeyer collection flask. Fifteen ml of 40% cold sodium hydroxide were added 25 35 A O Transmittance % h \J'I 55 32 I I . I I I I I I I I . . I I I I I .07 .09 .11 .13 .15 .17 .19 .21 .23 .25 .27 ng/ml Figure 1. Standard curve for adjusting myofibril fragmentation measurements 33 to the digestion flask. Steam was directed from the boiling water flask through the closed system so as to enter the sample, the condenser and the Erlenmeyer flask. After 7 min distillation, the collection flask was lowered and the condenser was flushed for 3 minutes. The 2% boric acid solution was titrated to the green end point with .0094 N sulfuric acid. The percentage protein was determined from the nitrogen analysis by using the factor of 6.25 X nitrogen. Statistical Analysis The statistical analysis was done by a CDC 6500 computer at the Michigan State University Computer Laboratory. Simple correlation coefficients were determined as described by Snedecor and Cochran (1969). Data were analyzed by three-way double split plot analysis of variance within each sex group. Where significance was indicated, individual comparisons were performed with t-test to determine which means were significantly different in both experiments (Rohlf and Sokal, 1969). RESULTS AND DISCUSSION Postmortem Temperature Changes Internal loggissimus muscle temperatures were monitored to determine relative chilling rates (figure 2). The data presented in ’figure 2 are those from experiment 2. The fat carcasses had higher initial internal temperature than the thin carcasses. The average initial internal temperature of fat carcasses was 39.2500 and that of thin carcasses was 38.1500. The normal cattle body temperature is approximately 38. 3°C to 39.1°C (Hafez, 1968). The internal temperature of fat carcasses exceeded the range of normal live cattle body tempera- ture. Struggling at death as well as the exothermic effect of post- mortem metabolism led to an increase in heat production and this heat increment probably caused high carcasses internal temperature. The fat carcasses had thick subcutaneous fat that is a good heat insulator and could keep a high internal temperature fbr a long time. Consequently, fat carcasses had higher internal temperatures than thin carcasses. Significant temperature differences could be found after the carcasses were in the chilling cooler for 2 hours. Slow chilling causes slower temperature decline than did fast chilling and temperature decline in fat carcasses was slower than thin carcasses. Muscle temperatures of fat carcasses that were fast chilled were considerably lower than those of thin carcasses that were chilled slowly. Thus, carcass fatness had an effect on chilling rate. 34 TEMPERATURE (°C) 35 25 15 10 35 FAT FAST CHILLING FAT SLOW CHILLING THIN FAST CHILLING THIN SLOW CHILLING DIOI s 0 2 4 6 8 IZI tI//// SI 1/ I732 TIME POSTMO RTEM (hr) Figure 2. Rate of temperature decline in beef-type steers 36 Postmortem Changes of pH The postmortem pH decline is the easiest way to estimate the conversion of glycogen to lactic acid (Bate-Smith and Bendall, 1949; 1956; Bendall, 1960; Cassens, 1966). In experiment 1 the rates of pH decline during the first 4 hr were similar for cows, bullocks and Helstein steers. The fat carcasses had faster pH fall than did the thin carcasses and the fast chilling rate (0°C to 1°C) caused the pH to drop more slowly than did slow chilling (15°C to 16°C) (figures 3 to 10). As indicated in the figures 5 and 6 the fastest mean pH decline of Holstein steers was those in carcasses with the thickest fat and chilled in the 15°C to 16°C cooler. It took only 2 hr to attain a constant pH level. The slowest mean pH decline was found in the carcasses with thin fat and chilled in the 0°C to 1°C cooler. It took almost 12 hr to reach a constant pH level. After 44hr postmortem, the lepes of all curves for cows, bullocks, fast chilling, slow chilling, fat and thin groups decreased gradually until they reached their lowest pH values. The patterns for Helstein steers were similiar to those for cows and bullocks, except that no further pH decline was noted in the fat group with slow chilling after 41hr postmortem. This suggests that the fatter the carcass is and the higher the chilling temperature, the more rapid the glycolytic rate. On the other hand, the thinner the carcass is and the lower the chilling temperature, the slower the glycolytic rate. When all the ATP or glycogen is depleted, the ultimate pH is reached or very closely 6.8 6.6 6.4 6.2 6.0 5.8 5.6 5.4- 5. 2 37 0 FAST CHILLING .\ 0 SLOW CHILLING O I O O ’>\ H H H - 0 2 4 6 8 12 24 48 192 TIME POSTMO RTEM (h r) Figure 3. Rate of pH decline in fat cows muscles with fast and slow chilling 38 7.0 6.8 6.6 6. 4 6.2 6.0 5. 8 5. 6 5.4 o FAST CHILLING o SLOW CHILLING \X 51 I 02468 12'24'48192 TIME POSTMORTEM (hr) Figure 4. Rate of pH decline in thin cows muscles with fast and slow chilling I —P —— 6.8‘ 6.6 6.4 6.2 6.0 5.8 5.6 5.4 5.2 39 0 FAST CHILLING 0 SLOW CHILLING :1 X If JL M 1 o 2 4 6 8 12"24I'48fl192 TIME POSTMORTEM (hr) Figure 5. Rate of pH decline in fat Holstein steers muscles with fast and slow chilling pH 40 6.8 ' . FAST CHILLING o SLOW CHILLING 6.6 6.4 6.2 6.0 5.8 - 5.6 “#4ng \rn—a 5.4 5.2 '|-—||———1|——— 02468 1212448192 TIME POSTMO RTEM ( h r) Figure 6. Rate of pH decline in thin Holstein steers muscles with fast and slow chilling 41 6.8 ' . FAST CHILLING . SLOW CHILLING 6.6 Eb K 5.2 ” ' o 2 4 6 8 12 ” 24 ' 48 I792 TIME POSTMORTEM (hr) ' Figure 7. Rate of pH decline in fat bullocks muscles with fast and slow chilling --T- .11.. 6.8I 6.6 6.4 6.2 6.0 5.8 5.6 5.4 5.2 42 - FAST CHILLING 0 SLOW CHILLING . I/° ° . ape-lee; 12i 24 WI— 0 2 4 6 8 192 TIME POSTMORTEM (hr) Figure 8. Rate of pH decline in thin bullocks muscles with fast and slow chilling 43 6.8’ 0 FAST CHILLING 0 SLOW CHILLING 6.6 5.2 llf II J o 2 4 6 8 12H 24 ll487l192 TIME POSTMORTEM (hr) Figure 9. Rate of pH decline in fat beef-type steers mscles - with fast and slow chilling 6.8I 6.6 6.4 6.2 6.0 o FAST CHILLING 0 SLOW CHILLING 5.8 5.6 m / A ‘N/ 5.4 5'20 2 4 6 8 12I|24H48II92I Figure 10. TIME POSTMORTEM (hr) Rate of pH decline in thin beef-type steers muscles with fast and slow chilling 45 approached. The ultimate pH of the carcasses will be maintained fOr a period of time. At this point the carcass is considered to be in full rigor. After this period the pH rose slightly. In the study of Cassens and Newbold (1966) the rate of pH decline postmortem at 1°C was not slower than that at 15°C until several hours postmortem. In their later work, Cassens and Newbold (1967) reported that the rate at 1°C was faster than that at 5°C and close to the rate at 15°C. In the present experiment it appears that fatness provided an insulatory effect by retarding temperature fall and thus it had an important effect on the rate of pH decline. The mean ultimate pH values of the five fat cows with fast chilling and slow chilling treatments were 5.54 and 5.43, respectively, and those of the five thin cows were 5.60 and 5. 59, respectively. For the ten bullocks, the mean ultimate pH of the five fat sides with fast chilling and slow chilling treatments were 5.46 and 5.42 and those of the five thin bullocks were 5.47 and 5.46, respectively. For the ten Holstein steers, the mean ultimate pH of the five fat sides with fast chilling and slow chilling treatments were 5.5 and 5.46, respectively and those of the five thin sides were 5.46 and 5.46, respectively. These data are in agreement with those of Cook and.Iangsworth (1966) and Cassens and Newbold (1967). They reported that the ultimate pH attained at 1°C or 5°C was significantly higher than that attained at 15°, 25° or 37°C. The rates of pH decline in experiment 2 (figures 9 and 10) had the same pattern as that in experiMent 1. During the first 2 hr postmortem pH dropped very rapidly and then the rate decreased gradually until 4 hr postmortem. After 4 hr post— mortem the pH remained quite constant until 24 hours. Nest of the mean pH values at 24 hr postmortem were higher than those at 12 hours. There was little difference in the rate of pH decline between fat and thin steers, fast chilling and slow chilling in experiment 2. This observation could be due to the beef-type steers that we used in experiment 2 which had thicker muscles than the cattle in experiment 1. The mean ultimate pH in experiment 2 was similar to that in experiment 1. The thicker muscles showed a slower heat transfer rate and probably provided somewhat the same insulatory effect as carcasses with a high fat covering. The fat steers chilled at 15°C to 16°C had the lowest ultimate mean pH values, on the other hand, the thin steers chilled with the low temperature had a highest ultimate mean pH values. The mean ultimate pH values of the lean steers with slow chilling were higher than those of the fat steers with fast chilling. These results indicated that the insulatory effect of fatness caused a higher ultimate pH than the effect of chilling temperature. These data of experiment 1 and 2 once again confirm the statement of Cassens and Newbold (1967) that temperature affects not only the rate but also the extent of glycolysis. It is interesting to note that the mean pH of the five fat bullocks with fast and slow chilling reached their lowest pH value at 6 and 8 hr, respectively, and rose to a higher level pH respectively, (5.55 and 5.53) at 12 hr postmortem. After 12 hr the mean pH dropped gradually to 5.5 and 5.46, at 24 hours. 47 Panel Tenderness In experiment 1, steaks from either fat or thin carcasses treated with slow chilling had higher panel tenderness scores than those treated with fast chilling (tables 2 and 3). The same observation was reported by Locker and Hagyard (1963), Herring gt_ a_l_. (1965), Marsh and Leet (1966), Smith gt_ g1. (1971), Coll gt_ a_l_. (1964), Hostetler gt_ _a_._l_. (1970), Bouton gt_ g_l_. (1973), Hostetler gt_ gl_. (1975) and Field gt_ gl_. (1976). However, the differences in panel tenderness between fast and slow chilling of the fat group were not significant. These results indicate that fat carcasses with thick insulatory subcutaneous fat apparently eliminated the cold shortening effect. The differences of panel scores of steaks between fat and thin carcasses under the same chilling treatment showed a tendency for steaks from fat carcasses to be more tender than those from thin carcasses. These data agree with those of Bell (1939) who reported that leg roasts from fatter lambs were more tender than those from lean lambs. The differences between fat and thin carcasses were not significant except for the Holstein steers with fast chilling (P < .05, table 2). Comparisons of panel tenderness for steaks aged 8 days indicate that all 8 day steaks had higher panel tenderness scores than did the 2 day steaks. Steiner (1939) reported that rate of aging was dependent on sex, age and other factors, rate being faster in younger than in older animals and slower in steers than in cows. However, in experiment 1 only fat cows, thin bullocks and thin Holstein steers showed significant TABLE 2. MEANS OF PANEL TENDERNESS 0F cows AND HOLSTEIN STEERS a'b'c COWS Days Fat Thin postmortem Slow Fast Slow Fast 2 4.37 3.36 5.07 2-45 8 6.99 5.51 6.31 3.77 aStandard errors of bMean significant difference differences among treatment combination means P < '05 P < '01 Fat vs thin i .955 2.008 3.204 Fast vs slow i .603 1.391 2.203 2 vs 8 days i .669 1.543 2.244 HOLSTEIN STEERS Days FELI, Thin postmortem Slow Fast Slow Fast 2 6.17 5.14 5.55 2.98 8 6.87 5.60 6.61 4.72 3’Standard errors of bMean significant difference differences among treatment combination means P < '05 P < '01 Fat vs thin i .690 1.591 2.315 Fast vs slow i .688 1.588 2.308 2 vs 8 days :_.442 1.018 1.483 CA score of 9 == extremely tender, and 1 = extremely tough. 50 aging differences. In experiment 1, the simple correlation of tenderness on a pooled cows, bullocks and Holstein steers basis gave a highly negative (r = - .64, Pv< .01) correlation between panel tenderness and Warner- Bratzler shear (table 4). Similar correlation (r = - .68, PI< .01) was obtained in experiment 2 (table 5). These results would tend to lead to the conclusion that either the Warner-Bratzler shear or the panel tenderness could be used to estimate the tenderness of cooked samples. In exepriment 1, the initial pH and 4 hr postmortem pH were sig- nificantly correlated with panel tenderness, although the correlation coefficients were low (r = - .27 and - .30). Hewever, this relationship was not found in experiment 2. WarnereBratzler Shear In experiment 1, steaks from either fat or thin carcasses, 2 or 8 days postmortem aging, that were chilled slowly always had lower Warner-Bratzler shear values than those chilled rapidly (tables 6 and 7). These results indicate that steaks from slow chilled carcasses were more tender than those from fast chilled carcasses. Only the differences between slow and fast chilled thin carcasses were significant (P;< .05). TPhese data confirm the results of panel tenderness scores in that (differences between fast and slow chilled fat carcasses were not sig- Ixificant. However, in experiment 2, the differences in fast vs slow (shill of both fatness groups were significant. Thus, fatness did not 51 one. I S.Wm ”ram. umo.w.H o .03 .I. s a H. I 3. I 1:. I re. rm. 8. I S. 8. I 3. I use r rs mm. I he. I as. I am. As. mo. I so. me. ca. I as re so as. I oo. I mo. I mm. am. as. I am. no. NH. I as am rs NH. I ma. I rs. I mm. .ss. no. I as. so. on. I as e re OS. I ca. I rs. I mm. mm. as. I so. mo. we. I as 0 rs oo.e mm. we. cs. I mo. I so. I he. no. I OL. unassoesp one saw some oo.e mm. mm. I as. I . no. I mm. mo. I as. cosmos reasons: oo.H no. I as. I so. mm. so. I ma. eocwewo worse oo.e as. me. am. mo. am. I onswneoz oo.e me. I as. mo. I so. I someaaoo weasousaaaess oo.s mo. on. me. I soeecesosmwss oo.e we. I as. senses owosoowmm oo.a so. I sense mIs OO.H mmmgmfiflmv HmfidnH mmosxoaep seamed poespxo osspwdoz someaaoo soapmpsos nvmsoa “more muesHoosop o m as one our some reasons: noses seasonsscwese Irena ouosoosnm mrs Hosea as e s caresses o.o mMoQHHDm Q24 mmmmam ZHHBmHom .mzoo QHHoom mo mHmMA zmmzamm mezmHonhHOU ZOHBRAHmmOo mamsz .d mqm szzEm EmHonhmoo ZOHBamMOU Ema—Em .m @349 53 TABLE 6. MEANS OF WARNER-BRATZLER SHEAR (kg/cmz) OF cows AND HOLSTEIN STEERS a'b COWS Days Fat Thin postmortem Slow Fast Slow Fast 2 3.06 3.54 2.95 4.10 8 2.37 3.34 2.59 3.43 aStandard errors of differences among treatment bMean signifiigagt difference < combination means P '05 P‘< '01 Fat vs thin 1 .418 .965 1.404 Fast vs slow 1 .364 .839 1.221 2 vs 8 days i .336 .774 1.127 HOLSTEIN STEERS Days Fat Thin postmortem Slow F t Slow Fast 2 3.17 3.58 3-18 3-80 8 2.84 3.34 2.48 3.40 aStandard errors of bMean signifiicant giffgrence differences among treatment combination means ___P‘< '05 ?:E_'01 Fat vs thin i’.279 .644 ~93? Fast vs slow :_.291 .671 .977 2 vs 8 days i_.200 .462 .671 54 TABLE 7. MEANS OF wARNER—BRATZLER SHEAR (kg/0mg) OF BULIOCKS AND BEEF-TYPE STEERS a'b BUIlOCKS Days Fat Thin postmortem Slow Fast Slow Fast 2 3.18 3.71 3.54 4.13 8 2.92 3.22 2.66 3.10 aStandard errors of bMean significant difference differences among treatment combination means P'< '05 P‘< °Q£__ Fat vs thin :_.411 .949 1.381 _ Fast vs slow i .297 .685 .998 2 vs 8 days i .382 .881 1.283 BEEF—TYPE STEERS Days Fat 4__ Thin postmortem Slow Fast Slow Fast 2 2.93 3.46 2.99 3.40 8 2.50 2.85 3.23 3.51 8‘Standard errors of bMean significant difference differences among treatment . combination meanS' P‘< '05 P‘< '01 Fat vs thin :_.245 .514 .705 Fast vs slow i .122 .256 .351 2 vs 8 days i .226 .476 .650 55 have much effect on warner-Bratzler shear values in the beef-type steers. Within the same chilling treatment, steaks from the fat carcasses almost always had lower Warner-Bratzler shear values, than those from thin carcasses, but none of the differences was significant. This indicated that fatness has some effects on meat tenderness but the effect is not as great as temperature treatment during postmortem chilling. Steaks from carcasses aged 8 days postmortem always had lower shear values than those from carcasses with 2 days postmortem aging. In experiment 1, significant postmortem aging effects were observed in steaks from thin cows chilled rapidly, thin Holstein steers and thin bullocks from both the fast and slow chilling treatments (table 6). These data suggest that postmortem aging effectively improved the adverse tenderness effects of cold shortening. In experiment 2, steaks from carcasses chilled slowly had lower warner-Bratzler shear values than those from fast chilled carcasses and the differences from both the fat and thin carcasses were significant (table 7). This observation once again demonstrates that fatness did- not have a marked effect on cold shortening in beefhtype steers. There is one interesting fact that after 8 days postmortem aging, steaks from fat carcasses with either slow or fast chilling, were more tender than those from thin carcasses (p.< .01). However, at 2 days postmortem, steaks from the same chilling treatment regardless of carcass fatness had almost identical shear values. POStmortem aging did not improve the 56 tenderness of steaks from thin carcasses, in fact they became tougher. This observation suggests that postmortem aging was more effective on fat beef-type steers than on thin beef-type steers. Sarcomere Length Sarcomere length is a measure of the contraction state of the muscle (Herring gt,al,, 1967). In 1960, Locker concluded that there was a relationship between postmortem shortening and tenderness. Using ox muscles excised soon after slaughter, Marsh and Leet (1966) and Davey gt_al, (1967) reported that shortening by up to 20% of the ex- cised length produced relatively small changes in tenderness, whereas further shortening from 20 to 40% produced a several-fold increase in shear value. With still further shortening there was a progressive decrease in toughness until at 60% shortening shear values were of the same order as those obtained at 20% shortening or less. The sarcomeres of freshly excised ox muscle are about 2.5 pm long (Davey gt al,, 1967), so that 20% and 40% shortening corresponds to a sarcomere length of about 2.0 pm and 1.5 pm, respectively. In experiment 1, the sarcomere of the lgggissigg§_muscle from the slow chilled carcasses were longer than those chilled rapidly (tables 8 and.9). These results agree with those of'locker and Hagyard (1963). ‘However, the mean sarcomere lengths from the slow chilled carcasses were not significantly different from those of the fast chilled carcasses. These results are contrary to the observation of Welbourn gt a_l_. (1968) 57 and Smith 239. a_l_. (1969) but confirm the data of Hegarty and Allen (1975). Stromer and Coll (1967) examined the muscles of seven heifers using phase microsc0py at various times and temperatures and reported that the myofibrils held at 2°C and sampled 24 hr postmortem were super- contracted and exhibited a pattern of alternating light and dark bands. In contrast, the myofibrils held at 16°C and sampled at 24 hr exhibited a marked thickening of the A-band, a shortening of the I-band, and a replacement of the H—zone by a dark line or hand. There were no sarcomere length differences between fat and thin carcasses or among the sex groups (tables 8 and 9). Smith gt_ a_l_. (1976) studied 40 lambs with thick, intermediate and thin finish and reported that increased ' quantities of fat sustained less shortening of sarcomeres. Perhaps different species of animals may differ in their response to the effect of fatness on sarcomere length. Postmortem aging did not have a sig— nificant effect on sarcomere length between fat or thin carcasses or between fast and slow chilling rate. Samples obtained after 8 days postmortem aging did not have as distinctive A-bands and I-bands as those from the 2 day samples and numerous short fragments were observed in the 8 day myofibril suspension. These findings confirm the data of Stromer and G011 (1967) in that variability in appearance was greater in 'the samples removed 312 hr postmortem and most of the myofibrils isolated Iaiter 312 hr postmortem storage at 2°C were supercontracted, thereas ‘those isolated after 312 hr postmortem storage at 16°C were only slightly contracted. No significantly different sarcomere lengths were fOund between cows, bullocks and Holstein steers (tables 8 and 9). 58 TABLE 8. MEANS OF SARCOMERE LENGTH (pm) OF cows AND HOLSTEIN STEERS a'b COWS Days Eat. Thine postmortem Slow Fast Slow Fast 2 1.97 1.81 2.04 1.78 8 1.87 1.75 1.91 1.77 3‘Standard errors of bMean significant difference differences among treatment < < combination means P '05 P '01 Fat vs thin :_.126 .292 .423 Fast vs slow i .141 .326 .473 2 vs 8 days :_.008 .188 .027 HOLSTEIN STEERS Days Fat Thin postmortem Slow Fast Slow Fast 2 1.95 1.86 2.05 1.85 8 1.83 1.75 1.92 1.81 aStandard errors of bMean significant difference differences among treatment P‘< .05 P‘< .01 combination means ___ ______ Fat vs thin :_.050 .130 .168 Fast vs slow :_.O50 .130 .168 2 vs 8 days i .050 .130 .168 59 TABLE 9. MEANS OF SARCOMERE LENGTH (pm) OF BULIDCKS AND BEEF-TYPE STEERS a'b BUIlDCKS Days Fat Thin_ postmortem Slow Fast §lgw_ Fast 2 1.94 2.02 1.92 1.89 8 1.86 1.88 1.84 1.82 aStandard errors of bMean significant difference differences among treatment P‘< .05 P‘< .01 combination means ___ Fat vs thin : .100 .250 .336 Fast vs slow i .060 .150 .201 2 vs 8 days 1 .090 .210 .302 BEEF-TYPE STEERS Days Fat Thin postmprtem Slow Fast Slow Fast 2 1.85 1.81 1.84 1.86 8 1.69 1.75 1.75 1.76 a'Standard errors of bMean significant difference differences among treatment combination means P1< '05 .___ P‘< '01 Fat vs thin + .045 .095 .130 ‘Fast vs slow .045 .095 .130 l+l+l 2 vs 8 days .055 .116 .158 60 In experiment 2 chilling treatments did not cause any differences in sarcomere length of myofibrils from either fat or thin carcasses (table 9). Sarcomeres from fat carcasses, irrespective of chilling rate had almost the same length as those from thin carcasses. These data indicate that cold shortening does not have any effect on beefetype steers regardless of fatness. POStmortem aging results in myofibrils shortening similar to that observed in experiment 1 (tables 8 and 9). In experiment 1, sarcomere length was not significantly correlated with either Warner-Bratzler shear (r = - .18, table 4) or the panel tenderness score (r = .19)o In experiment 2, similar correlation coefficients were obtained except the sign of the coefficients were reversed (table 5). Fragmentation Myofibril fragmentation was read spectroPhotometrically as percent transmittance thus the more myofibril fragments there are, the lower the percent transmittance reading. Myofibril fragmentation is associated with meat tenderness and as fragmentation increases, tenderness generally increase also. Thus myofibril fragmentation was determined in this study to assess the effect of cold shortening on the extent of fragmen- tation. In experiment 1, the fragmentation readings obtained from .loggissimus muscle samples from slow chilled carcasses were almost always Slower than those from fast chilled carcasses. Then 8 day postmortem samples were lower than those from the 2 day postmortem samples 61 (tables 10 and 11). These findings indicate that elevated chilling temperatures and postmortem aging increased myofibril fragmentation. Olson gt_gl, (1976) reported that fragmentation during postmortem aging was muscle and temperature dependent. In experiment 2, longissimus muscles from slow chilled carcasses had lower transmittance readings (more fragmentation) at 2 days postmortem, but at 8 days postmortem these same samples did not always have lower transmittance readings than fast chilled carcasses. Chilling treatment appeared to have a greater effect on myofibril fragmentation in beef-type steers than postmortem aging, however, none of these differences was statistically significant (P > .05). In experiment 1, fragmentation was highly associated with panel tenderness (r = - .45, PI< .01, table 4) and Warner-Bratzler shear (r = .50, P < .01). Comparable correlations were observed in experiment 2 (table 5). Intramuscular Collagen In experiment 1, neither chilling temperature, nor postmortem aging differed significantly (I’< .05) in percentage intramuscular collagen in the longissimus muscle of fat and thin carcasses of cows, bullocks or Hbdstein steers (tables 12 and 13). The percentage collagen of the Emssimus muscles of cows, bullocks and Holstein steers essentially did not differ and these results agree with those of G011 pt p1. (1963), McClain at al. (1965) and Herring gt_ a1. (1967) in that as tenderness dLecreased due to increased animal age there was essentially no change in 62 TABLE 10. MEANS OF FRAGMENTATION OF cows AND HOLSTEIN STEERS a'b'c COWS Days Fat Thin postmortem Slow Fast Slop Fast 2 38.73 38.00 36.20 43.77 8 28.98 22.68 29.70 38.01 aStandard errors of bMean significant difference differences among treatment P‘< .05 P'< .01 combination means Fat vs thin i_7.963 18.362 26.716 Fast vs slow i 2.827 6.519 9.485 2 vs 8 days i_2.503 5-771 8-398 HOLSTEIN STEERS Days Fat Thin postmortem Slow Fast Slow Fast 2 32.18 39.07 39.94 51.62 8 33.22 37.38 31.62 41.35 3Standard errors of bMean significant difference difference among treatment ‘< combination mepns P '05 P:E_101 Fat vs thin :_8.388 19.343 28.144 Fast vs slow :_5.836 13.457 19.580 2 vs 8 days i_5.046 11.636 16.929 cPercent transmittance per mg nitrogen. 63 TABLE 11. MEANS OF FRAGMENTATION OF BUIlDCKS AND BEEF-TYPE STEERS a'b'c BUIlDCKS Days Fat Th_in postmortem Slow Fast Slow Fast 2 39.93 48.05 38.40 45.46 8 38.14 34.48 33.61 35.75 aStandard errors of bMean significant difference differences among treatment < < combination means P '05 __ P '9: Fat vs thin i 8.055 14.982 27.025 Fast vs slow :3; 2.351 4.373 7.888 2 vs 8 days 1', 7.137 13-275 23-945 BEEF-TYPE STEERS Days Fat Thin postmortem Slow Fast Slow Fast 2 28.51 35.60 32.55 34.29 8 27.79 28.61 33.34 32.20 aStandard errors of bMean significant differenge differences among treatment combination means P < '05 __ i< ‘01 Fat vs thin : 3.285 6.902 9.14514. Fast vs slow i 2.311 4.855 6.651 2 vs 8 days i 2.324 4.883 6.688 cPercent transmittance per mg nitrOgen. 64 total amount of collagen present in muscle. These authors also observed that although tenderness of muscle increased due to postmortem aging, there was little change in the total collagen during the postmortem aging period. The results of experiment 2 were similar to those in experiment 1, however, the percentage intramuscular collagen of beef-type steers was much lower than that of the cattle studied in experiment 1. This obser- vation indicates that constitution of beef-type steers muscles differs from cows, bullocks and Holstein steers. These data also Show that the differences in tenderness were due to factors other than quantity of intramuscular collagen. In both experiment 1 and 2 (tables 4 and 5), the intramuscular collagen percentage was not correlated with panel tenderness, warmer» Bratzler shear or sarcomere length and fragmentation. Thus connective tissue content did not have an effect on muscle tenderness, extent of contraction or postmortem aging. Moisture, Marbling and Ether Extract At 4Ihr and 8 days postmortem, pH was correlated with moisture content in experiment 1 (r = .32 and .28, p.< .05, table 4) and in experiment 2 (r = .34 and .36, PI< .05, table 5). In experiment 1, percent moisture content was negatively correlated with panel tenderness (r = - .27, p.< .05) but was not significantly correlated with Warner-Bratzler shear (table 4). In experiment 2 the 65 TABLE 12. MEANS OF PERCENTAGE INTRAMUSCULAR COLLAGEN OF COWS AND HOLSTEIN STEERS 8“” COWS Days Fat gThin postmortem Slow Fast gig; Fast 2 6.77 6.75 7.26 7.18 8 6049 7033 7021+ 7031+ aStandard errors of bMeap significant difference differences among treatment P-< 05 P‘< 01 combination means ' ' Fat vs thin i_.996 2.297 3.241 Fast vs slow 3; .385 .887 1.292 2 vs 8 days i .460 1.062 1.543 HOLSTEIN STEERS Days Fat Tpin postmortem Slow F t Slow Fast 2 7.33 7.11 6.88 7.25 8 7.05 7.29 6.99 6.90 3’Standard errors of bMean significant differpnce differences among treatment compination means __P < :95 _ P< '01 Fat vs thin i_.611 1.408 2.050 FaSt vs 510“ i 0399 .920 1.339 2 vs 8 days 1; . 1.029 1.496 QPercent of fresh tissue. 66 TABLE 13. MEANS OF PERCENTAGE INTRAMUSCULAR COLLAGEN OF BULIOCKS AND BEEF-TYPE STEERS a'b'c BULLOCKS Days Fat Thin postmortem Slow Fast Slow Fast 2 5.94 5.62 6.80 6.77 8 6.70 5.98 6.27 5.91 aStandard errors of bMean significant difference differences among treatment P‘< .05 P‘< .01 combination means Fat vs thin i 1.231 2.838 4.130 Fast vs slow 1, .487 1.123 1.634 2 vs 8 days i, .634 1.462 2.127 BEEF-TYPE STEERS Days Fat Thin postpprtem Slow Fast Slow Fast 2 5.19 4.99 5-49 5.35 8 5.28 5.42 5.52 5.80 aStandard errors of bMean significant differencg differences among treatment combipption means P ::_'05 P‘< '01 Fat vs thin : .514 1.080 1.479 Fast vs slow 1_.255 .536 .734 2 VS 8 days i 0286 .601 .823 ‘ 9Percent of fresh tissue. 67 same results were obtained (table 5). These data indicate that organo- leptic determination of tenderness was better than mechanical shear to determine meat tenderness. In experiment 1, there was a low correlation between moisture content and sarcomere length (r = .21) but no relation- ship between moisture content and fragmentation was observed. However, in experiment 2, no relationship was shown between moisture content and fragmentation. As expected, ether extract was highly associated with moisture content in both experiments (r = - .93 and - .95). Thus fat animals had lower water contents than thin animals. The high correlation in experiment 1 (r = .85) and experiment 2 (r = .74) between marbling degree and percent ether extract agree with the results of others (WOoten pp_§;,, 1974; Dikeman §p_§l., 1972). Degree of marbling was highly negatively associated with percent moisture in experiment 1 (r = - .76) and experiment 2 (r = - .79). In both experiments, degree of marbling showed nonsignificant correlations with panel tenderness and warner-Bratzler shear value which agreed with Tuma _e_1_:_ a_l_. (1962), Romans gt_ a. (1965), Breidenstein .ei a_l_. (1968), and Berry 21 21.. .(1974). ' Twelfth rib fat thickness was highly correlated with ether extract, marbling degree and moisture content in experiment 1. Hewever, in experiment 2 marbling was correlated with twelfth rib fat thickness, but the correlation was low. This indicated that beef type steers with thick subcutaneous fat did not always have more intramuscular fat. In both experiment 1 and 2, chilling treatment and postmortem aging 68 did not have a significant effect on the percent moisture (tables 14 and 15) and ether extract (tables 16 and 17) of the lopgissimus muscle. In experiment 1, the percent moisture and ether extract from cattle differing in fatness were widely different, however, in experiment 2 there was little difference between fat and thin carcasses, and the marbling scores of the cattle in experiment 2 were also very similar (table 18). The latter observation may possibly explain why the cold shortening response was similar in fat and thin beef-type steers, even though the extent of fat thickness differed widely. 69 TABLE 14. MEANS OF MOISTURE OF cows AND HOLSTEIN STEERS a'b'c COWS Days Fat Thin postmortem Slow Fast Slow Fast 2 72.67 72.57 73.31 75-39 8 72.74 72.17 75.16 75.29 8’Standard errors of bMean significant difference differences among treatment combination means P < '02; P < '01 Fat vs thin 1; 1.153 2.659 3.868 FaSt vs 510" i 0290 .669 0973 2 vs 8 days i .241 .555 .809 HOLSTEIN STEERS Days Fat Thin postmortem Slow Fast Slow _F_‘a_s_p 2 70.90 71.54 75.12 75.18 8 70.54 70.54— 74.75 75.09 8'8th errors of bMean significant diffprgnce differences among treatment combination means __ P < '05 __ __ P < ‘01 Fat vs thin 1; 1.744 4.021 5.851 Fast vs slow 3; .947 2.183 3.177 2 vs 8 days i .977 2.252 3.278 C:Percent of fresh tissue. 70 TABLE 15. MEANS OF MOISTURE OF BULLOCKS AND BEEF—TYPE STEERS a'b'° BULLOCKS Days Fat Thin postmortem Slow Fast Slow Fast 2 73-53 73-63 73.85 73-43 8 _72.82 72.87 73.98 73.96 8‘Standard errors of bMean significant difference differences among treatment combination means P‘< '05 __p P‘< 'O¥__ Fat vs thin i_1.000 2.307 3.355 Fast vs slow i_ .430 .992 1.443 2 vs 8 days i_ .547 1.261 1.835 BEEF-TYPE STEERS Days Fat Thin__p postmortem Slow Fast Slow Fast 2 72.03 72.21 72.54 72.70 8 72.16 72.00 72.24 72.30 aStandard errors of Mean significant difference differences among treatment combination means _ P < '05 P < '01 Fat vs thin :_1.460 3.067 4.202 Fast vs slow i_ .315 .662 .907 2 vs 8 days :_ .405 .851 1.166 CPercent of fresh tissue. 71 TABLE 16. MEANS OF ETHER EXTRACT OF cows AND HOLSTEIN STEERS a'b'° COWS Days Fat Thin postmortem Slow F t Slow Fast 2 3.78 3.91 1.52 1.60 8 3.65 4.16 1.47 1.28 aStandard errors of bMean significant difference differences among treatment combination means P < '05__ P < '9: Fat vs thin + 1.265 2.917 4.244 Fast vs slow i .297 .684 .996 2 vs 8 days i .036 .438 .121 HOLSTEIN STEERS Days Ea; Thin Pp stmortem Slow Fast Slow Fast 2 6.03 5.80 1.03 1.26 8 6QM9 6.83 1.13 1.1+1 3’Standard errors of Mean significant difference differences among treatment P < . 05 P < . 01 combination means __ __ Fat vs thin _-I; 2.325 5.361 7.800 Fast vs slow i .973 2.243 3.264 2 vs 8 days _-|; .953 2.197 3.197 CPercent of fresh tissue. 72 TABLE 17, MEANS OF ETHER EXTRACT OF BULLOCKS AND BEER-TYPE STEERS a'b'° BULLOCKS Days Fat __Thin postmortem Slow Fast Slow Fast 2 2.31 2.16 1.62 1.58 8 2.77 2.67 1.54 1.71 8‘Standard errors of bMean significant difference differences among treatment P <:.05 PI< .01 combination meapp, ___ Fat vs thin i_1.064 2.453 3.570 Fast vs slow i .436 1.005 1.463 2 vs 8 days i .509 1.174 1.708 BEEFBTYPE STEERS Days Fat Thin postmortem Slow F t Slow Fast 2 3.73 3.41 3.17 3.17 8 3.79 4.19 3.51 3.89 aStandard errors of bMean sigpificant difference differences among treatment combination means P < '05 P < '01 Fat vs thin _-|_-_ 1.816 3.815 5.226 Fast vs slow i .504 1.059 1.451 2 vs 8 days i .456 .958 1.312 _— °Percent of fresh tissue. 73 TABLE 18. MARBLING SCORES a Fat Thin Cows 13ou' 502+ Bullocks 6.2 5.8 Holstein steers 15.2 4.8 Beef-type steers 25.4 20.8 a1 = practically devoid", 2 = practically devoid ° etc. SUMMARY This study consisted of two separate experiments to investigate the effect of cold shortening on bovine muscle and its relationship of sex, degree of fatness, postmortem aging and postmortem pH and tempera- ture decline. Ten cows, 10 bullocks and 10 Holstein steers were used in experiment 1, 20 beef-type steers were used in experiment 2. All cattle were slaughtered and divided into two groups (fat and thin) based on their fat thickness at 12th rib. All carcasses were split into right and left sides and placed in a -10 to 1°C chilling cooler (fast chilling) and 149C to 15°C chilling cooler (slow chilling), respectively. Internal temperatures and pH of the lopgipsimus muscle were monitored. At 2 and 8 days postmortem samples were removed from the lopgissimus muscle in the lumbar region for tenderness, sarcomere length, myofibrillar fragmen- tation, moisture, ether extract and collagen determinations. Tenderness was determined using Warner-Bratzler shear device and by taste panels. Sarcomere length was measured by use of a phase-contrast photo-microscope to detect the extent of muscle contraction. Myofibril fragmentation was read spectr0photometrically as percent transmittance. Postmortem temperature changes were fatness and chilling rate depen- dent. Fat carcasses had higher initial postmortem temperatures than thin carcasses. Slow chilling rate caused slower postmortem temperature de- cline than did fast chilling rates. Temperature decline in fat carcasses ‘was slower than thin carcasses. Carcasses fatness had an effect on cflrilling rate but could not overcome the effect of different chilling 74 75 temperatures. The fat carcasses had faster pH decline than did the thin carcasses and fast chilling rate caused the pH to decline more slowly than did the slow chilling rate. The ultimate pH attained in the fast chilled carcasses was significantly higher than those chilled slowly. There were no significant differences in postmortem pH decline among cows, bullocks and Holstein steers. The beef-type steers had the same pH decline pattern as the cattle in experiment 1 but there was little difference in the rate between fat and thin steers as well as between fast and slow chilling rates. Steaks from carcasses chilled slowly had higher panel tenderness scores and lower Warner-Bratzler shear values than those from fast chilled carcasses. Steaks from fat carcasses tended to be more tender than those from thin carcasses but only the differences in the thin group were significant. All 8 days steaks had higher panel tenderness scores and lower shear values than did the 2 days steaks. However, only fat cows, thin bullocks and thin Holstein steers showed significant aging effects in panel tenderness scores and only thin cows chilled rapidly, thin Holstein steers and thin bullocks differed significantly. In experiment 2, steaks from eitherche fat or thin carcasses chilled slowly had lower (PI< .05) shear values than those chilled rapidly. Fatness did not have much effect on shear values in the beef-type steers. After 8 days postmortem aging, steaks from fat carcasses had lower shear values than those from thin carcasses (p.< .01). Pestmortem aging did not improve the tenderness of steaks from thin beef-type steers. The sarcomere of lopgissimus muscles from the slowly chilled carcasses were 76 longer than those chilled rapidly. However, the differences were not significant in either experiments 1 or 2. Steaks after 8 days post- mortem aging tended to have shorter sarcomere lengths than those after 2 days aging. Cold shortening did not have an effect on beef-type steers. Sarcomere length was not significantly correlated with panel tenderness or shear values in this study. Myofibril fragmentation was highly correlated with tenderness (PI< .01). Sample from slow chilled carcasses almost always had more myofibril fragmentation than those from fast chilled carcasses. Frag- mentation was not different among fatness groups. P0stmortem aging did not cause any significant change in myofibril fragmentation. No sig— nificant fragmentation differences were observed in beef-type steers. Neither chill temperature, nor postmortem aging differed significantly in percentage intramuscular collagen in the lopgissimus muscle of fat and thin carcasses of cows, bullocks or Holstein steers and beef-type steers. Intramuscular collagen percentage was not correlated with panel tenderness, shear or sarcomere length and fragmentation in either experiment. 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APPENDIX 9O m.H N.n m.sfi 0.0N m.eN e.NN m.om m.mm 0.0m o.mm onenese N s 3H as NN mN Nm mm mm mm Hm H n m« we mN mN Hm an on an on N m NH mN mN mN on em am on as N e NH HN mN mN mN an an an we N m on ON eN mN Nm mm mm mm as N m NH HN mN mN Hm mm mm mm we m a NH ON 2N mN on an an on m: N N 0H eN en fin mm mm an mm as N 8 en mfi HN mN on an mm mm m: n.fi 8 ma ON mN 0N on em mm mm H: mesaaano sees o.m o.ON m.MN m.eN o.mN N.Hm m.mm e.mm m.am m.mm emnnesa m ON eN NN om mm mm an mm mm Hm e HN mN eN NN Hm mm mm an an on m ON mN NN on em mm an on H: m: m mH sN mN on on mm mm mm as me 0 ON :N NN on Hm mm mm an o: as a ON nN NN Hm Nm em mm an an we m «N HN 0N on en en an an on me n HN mN 0N NN em mm mm mm mm es s ON mN nN aN mN Hm mm mm mm m: s we HN :N NN mN Hm mm mm mm H: wsaaafino seam we sN NH N m e m N H 0 sense: musednmgsop edema: ddsdq< .mnzon Eopnospmom msoanm> em whoovm omhplmmop ps9 ca madaoov Aoov ondenomeop mo spas :mm .H Ndvcmmm< 91 o.H N.N H.HH N.NH N.NH e.eN N.NN N.om m.sm o.Nm oNsHm>< H.H N NH NH 0N mN n.NN m.om NN NN em m.H N NH NH NN NN on em NN mm mm H.H N 0H NH 0N eN n.NN Hm n.2m Nm mm H N HH NH NH NN NN mm NN mm NN o N HH NH 0N eN NN NN om NN N: N N NH NH 0N NN NN mm on an Nm m. N N sH NH NN m.NN Hm em mm NN H m NH NH NN NN NN Hm mm NN NN H m.H N NH NH 0N NN m.om mm NN mm H 2 NH NH ON eN NN NN mm NN on NeHHHHNo Heme N.N N.NH o.HN N.NN N.NN N.NN n.HN N.em N.mm N.NN eNene>< N NH HN 2N NN m.NN m.om em m.nm NN em e NH HN eN NN on mm mm NN mm an N NH NN mN n.NN NN em Nm NN on mm m NH NN NN NN Hm em NN NN mm NN N NH 0N NN mN NN NN mm NN Nm Na 3 NH NN NN NN Hm mm NN NN NN NN N NH ON NN mN NN on n.Nm NN NN Nm m NH HN eN NN om NN em em NN NN N NN 0N NN mN NN NN NN em NN mm m NH NN NN NN NN om mm mm Nm on NeHHHHNo :eHN m: .#N NH .m. “N. s m N H o Hogans mudpwHNQSNp odomsz Hmsds< .mnzo: sopH05pmom macanm> pm mHomam mmhpnmwop case as seaflood Aoov endpsnogaop Ho memo :Nm .HH xfiosmmm< Raw data of pH decline in cows at various postmortem hours. Appendix III. Muscle pH Animal 192 24 12 number Fat group, slow chi ling O\N\O M\O WWWWW «JUN:f:icm UNUNUNUNUN GDHrUNUNm> UNUNUNUNUN \03; N30 WWWWW \0 WWWW Noses \0 WWWW \OCDOOCD \OW\OWW \OOCDCDD— I o O I I \0th"\ \ONONrio \O\OW\O\O \O-fl'NQ-fl' \0\O\O\O\O l 6 6 6. 6 6 2 1 3 2 4 Fat group, fast chi ling 92 O\N\Om\q WWWWW \o U'N-d'd' m O I O O I UNLrNLrNuNuN “NEWER UNUNUNUNUN \Od' (\d‘m WWWWW "390?. "3‘9 «)UNUNUNUN users \0 WWWW \OCDO\O® \OWWWW \OOCDCDB o o o o o \OQWWW \ONO\1-IO \0\OW\O\O \Od‘NM-fl; \6\O\O\O\0 2 1 3 2 4 Thin group, slow 0 03“.“.‘9"? UNUNuNUNUN CO\O\O\O\O WWWWW ‘9“?“2‘20‘2 UNUNHNUNUN (1') W00 W WWWWW coma “3°? WWWWW aeeew \O WWW\O "302850.“‘5 uauNuauNw> ch>0JCQHi O O O I O (\WCDQH “909% WWWWW {\\0 WWW) WWWWW \o WW\OCD O O O O O Inmu'unxn °§°9°.‘“3°§ UNUNHNUNUN seems \0 WWW\O MO O\O\€'\ \O\O WW\O \ONNNv-l \O\O\O\O\O sense \0\O\O\O\O nasaa \O\O\O\O\O (\VNCwa-f Raw data of pH decline in bullocks at various postmortem hours. Appendix IV. 192 24 12 Muscle pH Animal number Fat group, fast chi QQQQE UNUNUNUNUN sssss UNVNUNUNUN 0ssss WWWWW \O\Od'\OW WWWWW wees“ UNUNUNUNUN \O W-fl'NO W WWWWW (\WWH W WWW\O W QQWQH UNUNuNuNUN «>UNoxoau3 UNUNUN«SUN ON\OOW\O WW\O\OW W 30 w 20 m Fat group, slow chilling % sssss WWWWW \O-zl; WdWO WWWWW essss WWWWW \ONO WW\O WWWWW \OUquWO UNUNUNUNUN \0 "NM: UN WWWWW figflifi UNUNUNUNUN (I) WCD (\W WWWWW (xerDGDUN I O O O O UNVNU'NVNUN eases WNO WWW O O O C . \O\O\O\O\O W w B 20 w Thin group, fast chilling sssms WWWWW 999*“ UNUNUNUNuN *mssss WWWWW ssssm WWWWW sesse UNUNUNUNUN WWWWW (BBQ W\0 WWWWW ONO'NWD- o o o o o \OWWWW ONO N NO W\O\OW\O HONHH . . C C . \O\O\O\O\O fiiflqm «DVDUNVDWD 16 W 18 28 31 Thin group, slow 0 hilling 999i? UNUNUNUNUN Q§QQ§ UNUNUNUNUN WWW-3'4? WWWWW C'N-d‘d' WW O O O O I UNUNUNUNUN O'NVNN'T UNVN UNUNUNUNUN WW WWW WWWWW sense WWWWW "re see WWWWW QQ§§Q UNu>UNUNvN ONmNH \OVSU‘NNONO NOMBN O O O C 6 7 & 6 6 m N m 8 m Raw data of pH decline in Holstein steers at various postmortem hours. Appendix V. 192 24 12 Muscle pH Animal number Fat group, fast chilling sssss WWWWW \O WNO WW WWWWW \O\O\ON W O I D C . UNUNUNUNUN \O\O\O\o UN 0 O O O O uNuNUNuNuN \O\O\O\O L\ O I C O O uNuNLrNtnuN C\\O\O\0\O O C C O . UNLrNLrNUNuN C120 {\.\C2C\ O O O UNUNUNUNUN N “(D {\ON C O O C . \nxnu'NUNLrN ONOO (\‘O W\O\OW\O HQNB—N o o o o o \OWWWQ L\.\O (\N L\ \O\O\O\O\O 14 10 12 23 26 Fat group, slow chilling 9# UNWJWDUNUN UNUNUNUNUN NONO (\d' In G O O I I uNuNuNUNvN \0 (\-\L2 WW . I I . UNVNuNuNuN O C C C O uNuNtrNuNuN (D WL\L\L\ . O C O O mmmmm (I)\O (\NONO . C C C C UNUNNAU'NUN ON\O L\\O(I) WWWWW N\OCD\O(\ \OWWWW ficxoooooo \OVNVNUNU'N M\O®\O O \O WWW\O (\Wd'N {\ \O\O\O\O\O 14 1o 12 23 26 Thin group, fast chilling \Od’\0 0'): WWWWW WWWWW \0\O (\Wd‘ WWWWW “3‘99“.‘1 UNUNUNUNUN \O\O WL\\O WWWWW O O C I O UNUNUNUNUN CD [\\0 LEN WWWW\O WWWW\O 0(1)qu '\OW\OW\O smsss \OW\O W\O N\OC\£L\ C O I \O\O\O\O 7.0 13 11 9 25 15 billing Thin group, slow 0 WWWWW \O\O\Od' N WWWWW 9.0.9.3.". UNUNUNNNUN (\00 UNC'N . C I C O uNtrNuNu'NuN 0000 M WWWWW I O O O O Lnxntntnxn \O\O {\L\.(D O C I . \nu'NLrNUNuN O\O L\WO \O WWW\0 O\O (\ONs-l \OWWW\O dome: o o o o o WWWWO 6 6 6. 6 6 Raw data of pH decline in HOlstein steers at various postmortem hours. Appendix V. Muscle pH Animal 192 24 12 number Fat group, fast chilling snows “WWW“ \O “\0 WW “WWW“ sens“ “WWW“ \0\0\0\O 1n O O O I O mmtrwmn 0000 L\. C C C O I mmxntnm L\-\O\O\O\O O C O O . \nvntntntn CD\O L\\0 L\ “WWW“ ssssm “WWW“ O\OOL\O o o o o o “\O\OW\O r-IO\NL\.N \OW\OW\O L\\O (\NL\. \O\O©\O\O 14 1o 12 8 % Fat group, slow chilling 94 “\00 WW “WWW“ 00 [\d‘ W O O O . . mmmmm \O L\\O WW I C C I . unnxnxnxn (I)\OL\L\.\0 o o o o o mmnmm sssss “WWW“ CI)“ {\\O\O “WWW“ O\\O L\\O(D “WWW“ N\OCO\OC\. \OWWWW fi§QQQ v>ususuxvx onooxo O C O O C \oxnxnxnxo (\W-Q'N L\ \O\O\O\O\O 1h 10 12 8 % wasss “WWW“ “ssss “WWW“ \O\O {\W-fi' WWWWW Qfigfii uxuxuwusus \0\Oo “(\‘0 “WWW“ L\-\O\O L\-O\ “WWW“ C1) B0 (\N WWWW\O (1) {NW (:01 G I C I minnxnxo O®N\OC'\ '\OW\OW\O E9 :1 hil Thin group, fast 0 ('30?! O\N \OW\O “\O ON\ONL\ O. O I 7 6 fl 6 6 B 11 9 % U ng 3 hi Thin group, slow 0 (\\0 “3:3; “WWW“ “WWW“ \o\ooo:r-:r “WWW“ . o o o o tnxntntnxn \O\0\O\O("\ “WWW“ \O\O\O\O\O “WWW“ 00 {\BQ WWWWW 00 “We . . . O . \0 “WWW 99§Qfi «>U\U\U\u3 essos \O ““00 6 6 & 6 6 U 11 9 25 U Raw data of pH decline in Beef-type steers at various postmortem hours. Appendix VI. 192 % 12 hDH 8 Mass AMml mMa fwtwflhm Fat group, % “:93 ““3 W300 fifimfifimfifififi 3 1‘\333 “DVDUNQQ “RV-\VK‘AUR‘AVRWAW meeeeeieee mmmmmmnmmm 3 WWW\O\O WWW“ . C C C O . . C C . QQQQQQQQQQ C O O O O . QQQQQQQQQQ 33 ““003 WW“) WWWWV‘V‘URAVRW "3:5. ")‘Q‘E‘Q "3‘9 "3"! QQQQQQQQQQ \03 Qrozxo “\0 "DUN Half-\VRUKVR‘R‘AVKVKW QdemeQQQ QQQQQQQQQQ QQoooQOmQ QQQQQQQQQQ “)3; (\\0 ‘03 MN (\3 \O\O\O\O\O\O\O\O\O\O M w M s % w w w W fl H Fat group, slow chi ling \O\0 Qdeo-a-dd ‘n fifififififififififi (“W-3' memo-:1- mm: WWWWURWVKWVR"; “)Q-ifiiwzistfii QQQQQQQQQQ QQdQQwéQQQ QQQQQQQQQQ 3 WHEN“) “WWW“ O O I O I O O C O QQQQQQQQQQ WN\O\O\O3 “\3 “\O V‘fi‘fifimV‘m‘A‘fi‘fi "3")‘9 99999.")? QQQQQQQQQQ “"30 meo ”)0 “WW QQQQQQQQQQ “300 MO (1300 NW") M'\\O “NV-\W QQQQQ CDNs-IH3O “\O\O\O UR\O\O\O\O\OV.\V\‘AV\ \O3\OCD33OOV\3 \O\O\O\O\O\O\O\O\O\O M 43 M #5 % 47 w 49 50 51 (continued) Raw data of pH decline in beef-type steers at various postmortem hours. .Appendix VI. Muscle pH 192 M 12 Amml mma % 999Q{{:{93 QQQQQQQQQQ éifigiqiiiq QQQQQQQQQQ «\me O Q3'3' mm 0 O O O O O O O O O QQ‘OQQ QQQQQ “NOW ('23 InInInIn QQQQQQQQQQ 3 (nInInInIn3'3 InIn O C O O O C O O O I QQQQQQQQQQ swaeaénwna InInI-nnInI-nI-nI-nInI-n “meeeewsea InInInInInInWI-nI-nI-n m999999§9§ QQQQQQQQQQ QmmmdéQQQm QQQQQQQQQQ O O (\(\.O\O\O\O\\O (\- \O\O QQQQQQQQ QQiimfiifliQ 3 M 5 32 % W 38 W 40 a2 fiQQiiQQfiQQ QQQQQQQQQQ m3 InIn33' (nah!) QQQQQQQQQQ QQQQ3333QQ QQQQQQQQQQ 333 I93 «\er In\0 QQQQQQQQQQ O C O O O O . QQQQQQQQQQ 3 InInIn3 In\O “In“ I O C O C O . O . . QQQQQQQQQQ QQQQ3Q33QQ QQQQQQQQQQ In\O\O\O InInInI-nInIn QQQQQQQQQQ QQQQ33QQQm QQQQQQQQQQ HomaQQomQH QQQQQQQQQQ E" 303 Cnm33®33 E\O\O\O\O\O\O\O\O\O\O 3 O r... (I) § E, 5 m3 In\0 w 0 97 Appendix VII. Raw data of chemical and physical traits. A 1. Identification of variable number. Variable Variable Decimal number item places 1 Animal number 0 2 Sex a O 3 Chilling rate b O 4 Postmortem aging C 0 5 Fatness group d O 6 Panel tenderness e 2 7 ma shear, kg/cm2 2 8 Sarcomere length, pm 3 9 Fragmentation f 2 10 Moisture % 2 11 Ether extract % 2 12 Collagen % 2 13 12th rib fat thickness, cm 2 '14 Marbling score g 0 a 1 = cow. 2 = bullocks. 3 = Holstein steer. 4»: beef-type steer b 1 = slow chilling. 2 = fast chilling. C 1 = 2-day postmortem. 2 = 8-day postmortem. d 1 = fat group. 2 = thin group. e 1 = extremely tough. 9 = extremely tender f 1 = percent transmittance per mg nitrogen. g 1 = practically devoid -, 2 = practically devoid 0 etc. 98 Appendix VII. Raw data of chemical andgphysical traits. A 2. Raw datgg_5 Variable number 1 2 _3, 4 5 6 7 8 9 10 11 12 13. 14 02 1 2 2 1 533 351 1664 3910 7346 0364 736 076 10 21 1 2 2 1 367 429 1832 3035 7266 0256 648 076 11 03 1 2 2 1 580 283 1598 2568 7220 0420 843 076 11 22 1 2 2 1 700 285 1958 4072 7078 0585 596 102 18 04 1 2 2 1 575 323 1675 3254 7176 0454 843 127 17 07 1 2 2 2 350 261 1910 3850 7595 0042 635 001 01 05 1 2 2 2 334 346 1820 3177 7675 0042 796 013 01 08 1 2 2 2 275 400 1621 4725 7514 0152 670 025 09 06 1 2 2 2 458 337 1904 3342 7440 0136 719 025 07 01 1 2 2 2 466 369 1580 3910 7422 0266 849 025 09 27 2 2 2 2 567 280 1676 3372 7356 0157 656 038 07 30 2 2 2 1 550 294 1960 3134 7072 0486 545 051 08 19 2 2 2 1 575 325 1865 1905 7436 0086 689 051 02 20 2 2 2 1 692 285 2014 3654 7359 0118 703 051 06 29 2 2 2 l 367 375 1703 4339 7357 0282 507 051 08 16 2 2 2 2 484 358 1861 3315 7466 0140 687 025 05 17 2 2 2 2 650 312 1948 2970 7472 0112 534 025 04 18 2 2 2 2 500 328 1902 4902 7458 0124 601 025 04 28 2 2 2 2 642 267 1717 3314 7226 0324 477 025 09 31 2 2 2 1 333 ~332 1870 4210 7210 0361 545 038 07 14 3 2 2 1 675 327 1695 2952 7123 0624 726 038 11 10 3 2 2 1 659 267 1705 2430 7162 0366 766 051 18 12 3 2 2 1 417 366 1751 3862 7404 0398 756 051 11 23 3 2 2 1 542 349 1778 5492 6656 1144 698 102 21 26 3 2 2 1 508 364 1820 3952 6926 0882 648 102 15 13 3 2 2 2 383 396 1771 5150 7542 0094 621 013 04 11 3 2 2 2 359 304 1919 5170 7550 0124 694 013 04 O9 3 2 2 2 409 372 1859 3577 7566 0176 668 013 04 25 3 2 2 2 658 292 1692 3887 7383 0206 668 025 07 15 3 2 2 2 550 334 1792 2890 7504 0104 798 025 O5 33 4 2 2 2 542 351 1706 3734 7483 0076 639 025 05 32 4 2 2 2 442 387 1708 3964 7372 0156 567 025 O7 42 4 2 2 2 358 397 1789 3764 7488 0106 560 025 04 35 4 2 2 2 467 409 1684 3355 7377 0176 542 038 09 34 4 2 2 2 508 342 1708 ' 2982 7352 0161 590 051 07 40 4 2 2 2 430 308 1911 2861 7239 0419 528 051 08 36 4 2 2 2 708 294 1640 2631 6381 1444 661 064 15 37 4 2 2 2 558 360 1885 .2897 7213 0360 608 064 09 38 4 2 2 2 625 313 1726 2226 7238 0535 515 064 10 39 4 2 2 2 475 348 1838 3790 7159 0458 592 064 08 50 4 2 2 1 533 292 1734 2715 7104 0545 667 089 08 51 4 2 2 1 467 320 1995 3356 7112 0559 628 102 09 44 4 2 2 1 442 270 1784 2906 7224 0463 488 140 09 41 4 2 2 1 500 287 1613 3129 7214 0413 363 165 09 45 4 2 2 1 500 281 1701 3068 7130 0432 482 178 11 49 4 2 2 1 600 279 1651 2510 7163 0453 683 178 11 43 4 2 2 1 642 256 1990 2122 7201 0464 435 203 10 47 4 2 2 1 558 261 1648 2804 7343 0273 453 191 08 46 4 2 2 1 542 286 1711 3448 7260 0344 556 216 10 48 4 2 2 1 467 315 1711 2556 7245 0248 661 216 11 99 Appendix VII. Raw data of chemical andgphysical traits. A 2L Raw data Variable number 1 2 3 4 5 6 .7 8 9. 10 11 12 13 14 02 1 1 1 1 433 360 1759 4000 7330 0301 896 076 10 21 1 1 l 1 633 329 2276 3597 7356 0209 561 076 11 03 1 1 1 1 317 220 1904 2358 7254 0400 766 076 11 22 1 l 1 1 583 279 2019 4820 7188 0500 519 102 18 04 1 1 1 1 217 343 1893 4588 7207 0482 645 127 17 07 1 1 1 2 442 328 1992 3715 7553 0082 754 001 01 05 1 1 1 2 475 302 1804 2912 7706 0058 654 013 01 08 1 1 1 2 458 276 2256 4770 7510 0211 729 025 09 06 1 1 1 2 616 272 2179 3434 7481 0225 628 025 07 01 1 1 1 2 543 297 1974 3270 7406 0186 864 025 09 27 2 1 1 2 475 397 1681 2849 7424 0142 668 038 07 30 2 1 l 1 583 319 1752 3235 7301 0260 500 051 08 19 2 1 1 1 625 281 2071 3142 7412 0110 724 051 02 20 2 1 l 1 517 378 2027 5272 7374 0218 743 051 06 29 2 1 1 1 467 362 1878 3455 7294 0318 507 051 08 16 2 1 1 2 608 246 1957 3315 7380 0129 857 025 05 17 2 1 1 2 575 335 2082 4605 7404 0096 812 025 04 18 2 1 1 2 384 372 2037 5220 7489 0102 554 025 04 28 2 1 1 2 550 419 1839 3212 7230 0340 507 025 09 31 2 1 1 1 525 252 1961 4860 7383 0248 496 038 07 14 3 1 1 1 700 265 2120 2343 7234 0384 871 038 11 10 3 1 1 1 709 250 1992 2335 7138 0378 791 051 18 12 3 1 1 1 625 320 2139 2992 7382 0374 717 051 11 23 3 1 1 1 558 432 1774 4792 6723 1068 608 102 21 26 3 1 1 1 492 316 1736 3630 6972 0810 680 102 15 13 3 1 1 2 550 356 2177 4384 7608 0068 645 013 04 11 3 1 1 2 467 324 2091 4352 7556 0122 722 013 04 09 3 1 1 2 542 332 1954 3480 7559 0080 608 013 04 25 3 l 1 2 592 278 2068 3560 7378 0174 617 025 07 15 3 1 1 2 625 298 1975 2695 7460 0070 850 025 05 33 4 1 1 2 675 277 1791 3270 7421 0065 615 025 05 32 4 1 1 2 450 373 1785 4403 7321 0170 694 025 07 42 4 l 1 2 475 392 1959 2626 7458 0169 510 025 04 35 4 1 1 2 642 237 1768 3258 7335 0329 602 038 09 34 4 1 1 2 642 244 1789 3119 7361 0085 541 051 07 40 4 1 l 2 630 271 1809 3419 7306 0362 402 051 08 36 4 1 1 2 775 282 1895 2858 6837 0812 527 064 14 37 4 1 1 2 633 239 1853 2887 7253 0261 458 064 07 38 4 1 1 2 560 294 1849 3005 7200 0473 567 064 11 39 4 1 l 2 417 384 1927 3700 7049 0445 576 064 10 50 4 1 1 l 683 241 1903 3061 7310 0319 519 089 08 51 4 1 1 1 658 252 1824 2925 7083 0564 494 102 12 44 4 1 1 1 550 288 1532 2562 7251 0302 656 127 11 41 4 1 1 1 660 286 1721 3126 7256 0354 426 165 09 45 4 1 1 l 650 286 1926 2600 7118 0392 465 178 09 49 4 1 1 1 600 298 1872 3116 7251 0346 548 178 12 43 4 1 1 1 708 269 1841 2604 7147 0447 450 191 07 47 4 1 1 1 692 318 2013 2850 7214 0267 526 191 10 46 4 1 1 1 567 344 1903 2935 7224 0338 556 216 11 48 4 1 1 1 525 349 1974 2726 7173 0403 550 216 11 Appendix VII. 100 Raw data of chemical and physical traits.4rA 2., Raw dat§_f Variable number 1 2 3 4 5 6 7 8 9. 10 11 12 13 14 02 1 1 2 1 683 228 1818 3534 7435 0294 791 076 10 21 1 l 2 1 767 237 1973 2773 7373 0232 547 076 11 03 1 1 2 1 670 203 1842 2476 7292 0301 628 076 11 22 1 1 2 1 733 228 2061 3092 7122 0479 631 102 18 04 1 1 2 1 640 288 1679 2614 7149 0521 647 127 17 07 1 1 2 2 697 261 1981 3197 7551 0052 733 001 01 05 1 1 2 2 542 248 1905 2310 7638 0020 740 013 01 08 1 1 2 2 609 308 1915 3430 7510 0194 661 025 09 06 1 1 2 2 717 205 1936 2884 7457 0186 719 025 07 01 1 1 2 2 592 277 1788 3030 7424 0284 766 025 09 27 2 1 2 2 567 280 1672 3379 7353 0193 649 038 07 30 2 1 2 1 558 285 1893 2910 7114 0436 596 051 08 19 2 1 2 1 718 238 1761 3731 7452 0135 917 051 02 20 2 1 2 1 715 261 1992 3814 7315 0222 724 051 06 29 2 1 2 1 542 334 1740 4079 7281 0298 556 051 08 16 2 1 2 2 667 244 1822 3015 7402 0124 789 025 05 17 2 1 2 2 783 218 2015 2880 7512 0078 575 025 04 18 2 1 2 2 633 328 1906 3720 7458 0120 642 025 04 28 2 1 2 2 733 259 1784 3812 7266 0258 482 025 09 31 2 1 2 1 433 344’ 1904 4538 7248 0293 556 038 07 14 3 1 2 1 700 282 1924 2313 7121 0576 715 038 11 10 3 1 2 1 750 239 1794 2533 7124 0348 633 051 18 12 3 1 2 1 625 296 1817 3052 7368 0374 810 051 11 23 3 1 2 1 692 277 1782 4962 6650 1164 649 102 21 26 3 1 2 1 667 324 1821 3752 7007 0784 717 102 15 13 3 1 2 2 633 228 1908 3028 7544 0072 645 013 04 11 3 1 2 2 617 265 2002 3147 7468 0078 743 013 04 09 3 1 2 2 733 228 1874 2690 7568 0136 724 013 04 25 3 1 2 2 642 243 1878 4285 7325 0216 587 025 07 15 3 1 2 2 683 279 1934 2658 7472 0064 798 025 05 33 4 1 2 2 667 284 1758 4400 7359 0171 626 025 _05 32 4 l 2 2 567 347 1995 5553 7264 0183 584 025 07 42 4 1 2 2 416 331 1679 3268 7488 0103 510 025 04 35 4 1 2 2 517 366 1708 2660 7189 0529 597 038 09 34 4 1 2 2 517 302 1779 2777 7392 0100 580 051 07 40 4 1 2 2 508 314 1690 3121 7267 0285 398 051 08 36 4 1 2 2 783 237 1653 2313 6662 0979 565 064 14 37 4 1 2 2 683 310 1722 2753 7310 0159 495 064 07 38 4 1 2 2 560 360 1717 2686 7022 0670 572 064 11 39 4 1 2 2 430 380 1794 3812 7284 0334 590 064 10 50 4 1 2 1 671 249 1696 2635 7223 0326 650 089 08 51 4 1 2 1 633 292 1776 2871 7137 0428 577 102 12 44 4 1 2 1 592 211 1775 2568 7224 0307 470 127 11 41 4 1 2 1 592 285 1632 2735 7110 0548 421 165 09 45 4 1 2 1 500 219 1594 3132 7331 0269 505 178 09 49 4 1 2 1 558 310 1628 3074 7080 0561 686 178 12 43 4 1 2 1 758 222 1708 2318 7298 0356 428 191 07 47 4 1 2 1 600 229 1651 2923 7302 0244 539 191 10 46 4 1 2 1 542 229 1711 3112 7237 0385 467 216 11 48 4 1 2 1 617 257 1692 2422 7219 0363 541 216 11 101 Appendix VII. Raw data of chemical and physical traits. A 2l Raw data Variable number 1 2 3 4 5. 6 7_ 8 9 10 11 12 13 14 02 1 2 1 1 317 473 1669 4605 7377 0336 817 076 10 21 1 2 1 1 367 419 1825 4132 7279 0282 648 076 11 03 1 2 1 1 196 297 1762 3358 7291 0390 726 076 -11 22 1 2 1 1 583 339 1849 4460 7127 0520 580 102 18 04 1 2 1 1 217 235 1966 2444 7210 0426 604 127 17 07 1 2 1 2 200 408 1759 4180 7638 0086 733 001 01 05 1 2 1 2 241 409 1823 3480 7560 0076 759 013 01 08 1 2 1 2 233 397 1645 6185 7452 0208 670 025 09 06 1 2 1 2 275 460 2021 4072 7534 0146 638 025 07 01 1 2 1 2 275 378 1668 3970 7510 0386 791 025 09 27 2 2 1 2 375 526 1732 3477 7409 0123 673 038 07 30= 2 2 1 1 425 356 1803 3893 7214 0336 477 051 08 19 2 2 1 1 409 454 2186 5310 7441 0120 668 051 02 20 2 2 1 1 533 383 2159 5722 7420 0155 668 051 06 29 2 2 1 1 492 372 1987 3845 7366 0222 500 051 08 16 2 2 1 2 442 375 1781 3758 7472 0160 812 025 05 17 2 2 1 2 433 381 2064 4768 7536 0098 747 025 04 18 2 2 1 2 408 410 1984 7114 7532 0096 621 025 04 28 2 2 1 2 542 372 1867 3612 7266 0317 533 025 09 31 2 2 1 1 500 291 1989 5254 7375 0249 496 038 07 14 3 2 1 l 659 336 1989 3252 7305 0342 775 038 11 10 3 2 1 1 517 387 1774 2847 7158 0491 729 051 18 12 3 2 1 1 454 369 1950 4380 7410 0331 763 051 11 23 3 2 1 1 583 350 1800 5580 6756 1074 628 102 21 26 3 2 1 1 358 345 1800 3477 7140 0662 662 102 15 13 3 2 1 2 250 396 2024 5668 7540 0112 668 013 04 11 3 2 1 2 233 405 1779 5602 7500 0138 694 013 04 09 3 2 1 2 250 398 1797 5520 7616 0110 766 013 04 25 3 2 1 2 400 323 1803 3933 . 7432 0142 654 025 07 15 3 2 1 2 358 378 1848 5085 7504 0130 843 025 05 33 4 2 1 2 525 321 1720 2903 7429 0159 491 025 05 32 4 2 1 2 350 382 1685 2839 7312 0231 530 025 07 42 4 2 1 2 275 394 1865 3218 7551 0144 476 025 04 35 4 2 1 2 600 257 1893 3741 7312 0295 624 038 09 34 4 2 1 2 575 264 1767 3318 7393 0088 509 051 07 40 4 2 1 2 450 338 1806 3541 7214 0354 537 051 08 36 4 2 1 2 475 393 1997 3506 6799 0917 600 064 15 37 4 2 1 2 458 323 1904 3672 7281 0212 491 064 09 38 4 2 1 2 492 339 1847 3355 7221 0371 555 064 10 39 4 2 1 2 442 384 2102 4195 7186 0401 541 064 08 50 4 2 1 1 425 299 1869 3146 7292 0291 457 089 08 51 4 2 1 1 425 312 1845 3843 7229 0360 519 102 09 44. 4 2 1 1 425 384 1852 3368 7133 0436 497 140 09 41 4 2 1 1 425 420 1959 4205 7247 0237 405 165 09 45 4 2 1 1 460 353 1693 3810 7151 0427 517 178 11 49 4 2 1 1 542 327 1711 3476 7119 0533 632 178 11 43 4 2 1 1 442 327 1726 2808 7210 0396 422 203 10 47 4 2 1 1 592 308 1747 3452 7281 0284 508 191 08 46 4 2 1 1 542 360 1835 3854 7287 0188 504 216 10 48 4 2 1 1 442 366 1859 3640 7263 0253 530 216 11