EFFECT OF COLD STORAGE AND
FROZEN STORAGE ON THE

PALATABIUTY AND HISTOLOGICAL
APMARANCE OF THE LONGISSIMUS

DORSI MUSCLE OF BEEF

Thesis fer fhe Degree of M. S.
MICHIGAN STATE COLLEGE

Kathryn June Orr
1949

This is to certify that the

thesis entitled

Effect of Cold Storage and Frozen Storage
on the
Palatability and Histological Appearance
of the
Longissimns Dorsi Muscle of Beef
presented by

Kathryn June Orr

has been accepted towards fulfillment
of the requirements for

_M.:_§.:_ degree mm Nu‘brition

 

 

EFFECT OF GOLD STORAGE AND FROZEN STORAGE
ON THE
PALATABILITY AND HISTOLOGICAL APPEARANCE
OF THE
LONGISSIMUS DORSI MUSCLE OF BEEF

By
KATHRYN JUNE ORR

ATHESIS

Submitted to the School of Graduate Studies of Michigan
State College of Agriculture and Applied Science
in partial fulfillment of the requirements
for the degree of

MASTER OF SCIENCE
Department of Foods and Nutrition
School of Home Economics
1919

fi-KMA’STRY DEF“ r.

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ACKI‘JOWLEDGLE NTS

The writer wishes to acknowledge her sincere gratitude to
Dr. Pauline Paul for her guidance in choice of the problem and
her counsel throughout the study; to Er. Lyman Bratzler, Animal
Husbandry, for furnishing the animals and preparing the meat
for use; to Dr. William.Baten, Agricultural Experiment Station,
for statistical analysis of the data; to Hrs. Maura Bean for her
able assistance while writing the thesis; and to each member of

the taste panel for her aid in scoring the cooked meat.

INTRODUCTION . . . . . . .
DISCUSSION OF LITERATURE .
Beef'Muscle . . . . . .
Structure. . . . .
Composition . . .

Cold Storage Studies. .

TABLE

Definition and purpose

Palatability changes .

Flavor and aroma

Juiciness. . .
Texture. . . .

Tenderness . .

Histological changes

Chemical changes .

Oxidation of fat

Free fatty acid.

pH 0 O O O O O

Tenderness studies .

Shear values . . .

Tenderness variation

Cooking studies .

Freezing Storage Studies. .

Definition and purpose

Palatability changes .

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General palatability

Tenderness . . . .
Histological changes .
Chemical changes . . .
Tenderness studies . .

Shear value . . .

Tenderness variations

Cooking studies . . . . . .

EJCPERDAENTAL PROCEDURE . . . .
Description of meat . .
Preparation of samples
Method of cooking . . .
Chemical methods . . .

pH . . . . . . . .

Peroxide number. .

Free fatty acid .
Histological studies .
Statistical methods . .
DISCUSSION OF RESULTS . . . .
Palatability Changes . . .
Definition of terms . .
Appearance . . . . . .
Aroma . . . . . . . .
Flavor . ......
Lean . . . . . .

Fat . . . . . . .

Texture . ......
Tenderness . . . . . .

Juiciness . . . . . . .

Page
. 13

. 1h
. 16

. 17

. 20

. 20

. 21
. 22

. 22
. 22
. 2h

. 27
. 27

. 27
. 27
. 27
. 28

. 29

. 29

. 30

. 31
. 31

. 32

General conclusion . . . . . . .

Shear Measurements . . . . . . . . .
Cooking Changes . . . . . . . . . . .
Chemical Changes . . . . . . . . . .
Peroxide values of fat . . . . .

Free fatty acids in fat . . . . .

pH . . . . . . . . . . . . . . .
Histological Changes . . . . . . . .
EXplanation of descriptive terms

Rigor node . . . . . . . . .

wave . . . . . . . . . . . .

Others . . . . . . . . . . .
Disintegration . . . . . . .

Storage changes . . . . . . . . .

Cold storage . . . . . . . .

Frozen storage . . . . . . .

Breaks in fibers . . . . . . . .
SUNI‘ARY AND CONCLUSIONS . . . . . . . .
LIST OF REFERENCES . . . . . . . . . . .
APPENDIX . . . . . . . . . . . . . . . .

Page
. 36

. 38

55

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.59

. 67

Number Title re;
’1. As ‘u uwmsry of aging and s' rage treatments on steaks 22
for Animll I and Am ma

aranae of longissimus dorsi steaks 29

r’ ' n1. .\,~ a , . P a.
C. ILUL'U1 Shdltb nor Cl
’ frozen storage

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in cold storage “rd

3. Lean scores for aroma of lon-is sinus dorsi steaks in 30
cold storage ar1d frozen stor: ge

h. Le 1 sm ores for flavor of loan of longissimus dor31 ' 30
stea 1.3 in cold stox rage and fro «in store;

5. Keen sooxes for flavor of fat of longi'sinus dorsi 31
ates {s in cold stor: go and frozen storage

6. Kean scores for texture of longissimus dorsi steaks 32
in cold storIge and frozen storage

7. Lean scores for fenderness of longiss Lmus dorsi 33

steaks in cold storage and fzozen storage
8. Significant F values I: om an.a is of variance of 3S

tenderness scores

9. Kean scores for juiciness of longissimus dorsi steaks 30
in cold storage and frozen storage

13. been scores for general conclusion of longissimus 37
dorsi steaks in cold stcrsgc and frozen storage

11. Sig_iflcant F values from analysis of variance of 37
veneral cor; “in ion score

q ‘a 9 as. v ~ 1 _ ‘_' C‘
id. Correlation COefllClenLS bethen smear force readings Bo
and judges' scores on tenderness and texture of cooked

steaks

13. Summary of ave ges of combined Wvlbdqs of lonrissimus hO
ClOI‘bi buwflLS, OJ. COCLMii.g bible, a-ld COUl'tiIlg 10385 £1051
Animal I and Animal II

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ero: ‘de values of urfrm an and frozen raw fat from
ougISCIJus dorsi m soles of beef

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Title

Diagram of division of longissimos dorsi muscle inLo
Eu one-inch sieaks

Freezing rzurves for loxlgi sinus do rsi s;':ks aged at
no F. prior to freeziilg

htnges duling cold store ge of lonbissiius dorsi
fibers. (longitudind SGCoiOHS of uncoonod samples)

Chfinges during cold storage of longissimus dorsi
fibers. (lonbitudinal sections of uncooked samples)

HiL‘ or changes in cold storage of longissimus dorsi
fioexs. (longitudinal sections of uncooked samples)

.Lrege heat rigor produced
a;:lle of ion is:inus dorsi
es -ions of cooked samxles)

in cooked, cold storage
iiber (longioddinei

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Ciznges during frozen storage of longissimus dorsi
fibers. (lonoioidinii sections of uncooked samples)

Changes daring frozen storage of lorgiS'imus dorsi
fibers. (longitudinal secoions oi uncooLed samples)

Changes during freezing storage of longissimus dorsi
fibers. (iowéitvdinai sections of cooked samples)

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INTRODUCTION

Adequate preservation of meat is necessary to the economy of the
commercial packer, the locker Operator and to the individual.. Heat is
a highly perishable product and subject to alteration by enzymes, yeasts,
molds, and bacteria which.may render it unfit for human consumption.
The earliest preservation of meat was by salting and drying, but the
growing desire fOr the superior flavor of fresh meat, and a method fer
its preservation, led to the development of cold storage - first by the
use of ice and later by mechanical refrigeration. 'Within the past 25

years great progress has been made in the freezing preservation of meat.

For some meats, particularly beef, the practice of a limited
period of holding under refrigerated conditions (3h to 36°F.) improves
the tenderness and flavor of the meat. A period of aging from one or
two days to several weeks has been used in previous studies. In general,
it has been customary to age beef prior to freezing. fielding periods,
however, are not necessarily indicated for the freezing preservation of
beef. Gortner, et al.(l9h8) suggest that freezing may, and often should
be carried out shortly after slaughter. He further states, that during
the war Argentine beef destined for England was boned immediately after
killing and frozen while still warm. The resulting product was given

a high quality rating.

Many recent investigations on beef’muscle have indicated that the
freezing process itself’makes meat more tender and influences other
palatability factors. Thus it‘was deemed'worthwhile to study the effect
of both cold storage and freezing storage on the palatability and histo-

logical appearance of the longissimus dorsi muscle of beef.

- 2 -

The specific objectives of this problem were:

1.

2.

h.

S.

Tb compare rate of tenderization of beef held at hO-h5°F.
and at 00F.

Tb note palatability changes, especially in tenderness
and flavor, occurring in beef during ripening at hO—hSOF.
and at 00F.

To ascertain the percent cooking losses and cooking time
of unfrozen and frozen steaks.

To determine histological changes during storage of beef
and attempt to relate these with palatability.changes.

To determine peroxides and free fatty acids in the raw
fat during storage as an indication of development of
rancidity of the fat.

DISCUSSION OF LITERATURE
Beef Muscle
Structure

Sceletal muscle is made up of striated muscle fibers held
together by connective tissue and surrounded by a sheath of heavier
connective tissue. The fibers are arranged parallel to each other
in bundles called fasciculi. Each fiber is elongate, cylindrical and
nmltinucleated with elliptical shaped nuclei; some fiber ends are
tapered; others rounded. The fiber may terminate in a. tendon; one
end of the fiber may terminate in a tendon and the other end within
a muscle; or both ends of the fiber may terminate in the muscle. Each
fiber is encased in a thin, colorless, elastic membrane, the sarco-
lemma. The connective tissue around the fasciculi is called the
perimysium, and the sheath of connective tissue around the entire

muscle the epimysiumwaximow and Bloom, 19118 ).
Composition

The principal proteins within the muscle are mosin and myogen.
They are present in the colloidal state. The connective tissue consists
mainly of collagen which softens and swells in the presence of'dilute
acid. It is converted into gelatin by boiling or heating with super-
heated steam, the conversion being assisted by dilute acid(Ewell, 19140).
Elastin is also present in connective tissue, but it is resistant to
heat and breakdown by Inrdrolysisflowe, 191:3).

The prOportion of connective tissue present in a muscle is
considered by Lowe(l9h3 ), and other investigators, as a measure of
muscle tenderness. Mitchell, et a1. (1928) examined different retail

_ h -
cuts of beef for collagen content. The eye muscle(longissimus dorsi)
for calves showed the lowest content of collagen, expressed as total
nitrOgen. In studying the reliability of four comparable cuts from
one animal for obtaining palatability scores, Satorius and Child(l938)
concluded that the longissimus dorsi muscles of beef and pork possessed
homogeneous physical prOperties. The longissimus dorsi muscle was
chosen for the experimental work in this problem. Sisson and Grossman

(1938) have presented a concise, anatomical description of the longiss—

imus dorsi muscle.

Cold Storage Studies
Definition and purpose
Cold storage is generally defined as the holding of fresh beef
at 3h - 36°F. for varying periods of time. The primary intention of
aging meat after slaughter is to make it more tender(Bate-Smith, l9h8).
Numerous studies have reported palatability, histological and chemical

changes in beef held for various time periods.
Palatability changes

The chief factors of palatability of beef are flavor, aroma,
juiciness, texture and tenderness.

Flavor and aroma: Flavor and aroma scores follow similar patterns

 

from analyses of judges' scores. Harrison(19h7) and Paul, et al.(l9hh),
feund the greatest improvement in flavor and aroma of beef occurred
during the first 10 days of storage at 3h - 36°F. Further storage
brought about a "high" or "gamey" flavor in the lean, rancidity in the
fat, and a musty odor. Heagland, et al.(l9l7) reported that flavor

changed in two to four weeks cold storage. Whether or not the change

.. 5 -
in flavor was in the nature of improvement or deterioration was
subject to individual tastes. Lowe(l9h3) reported that maximum
deve10pment of desirable flavor in beef roasts was achieved in 20

to to days at temperatures a little above freezing.

Juiciness: Juiciness scores from various meat studies showed
a gradual increase with aging(Lowe, 19h3; Paul, at al., 19kt; Anon.,
1939b).

Texture: Texture is determined by the size of the bundle
fibers and the amount of connective tissue. The larger the fiber
bundles the more coarse the texture; conversely, small amounts of
connective tissue and indistinct bundles of fibers denote fine texture
(Ramsbottom, et al., 19h5; Brady, 1937). In a study on cooked
longissimms dorsi and other beef'mmscles aged.10 days, Brady(1937)
found that texture was an indication of tenderness and gave a high

positive correlation with the tenderness palatability factor.

Tenderness: One of the principal desirable effects of aging

 

on the organoleptic preperties of beef is usually considered to be a

marked increase in tenderness.

A comprehensive review of the principal studies pertaining to
storage and aging of beef has been made by Bate-Smith(l9h8). Particular
emphasis is placed on the tenderness of beef at temperatures above
freezing. All of the investigators whose work has been reviewed
agreed that the process of ripening in cold storage brought about the

desired tenderness effect.

Deatherage and Harsham(l9h7) found that tenderness did not

increase linearly with.postmortem age of'meat. "From tenderness curves

-6-
for each animal it is apparent that not all carcasses increase in
tenderness with age throughout the period of observation. The de-
crease in tenderness during the aging period in some carcasses appears
to be quite real as the data are outside the realm of experimental
error." Steaks from the loins of some carcasses tested at various
periods were found to be more tender than others. The meat of some
became less tender at times while meat from others increased progress-
ively in tenderness throughout the aging period. In general, tender-
ness increased until 17 days; from.l7 to 2h days there was no improvement
or a slight drOp in tenderness. At 2h to 31 days some improvement
beyond the 17 day tenderness level was noted. It was concluded that
unless beef is to be aged beyond approximately four weeks, it need
be aged only two and one-half weeks. Harrison(l9h7) also found that

increase in tenderness during aging was not linear.

Two Opposing theories relative to the effect of cold storage
and ripening of beef have evolved from.the numerous studies presented
herein:

1) Tenderness is due exclusively to an effect upon
muscle fibers(Hammond, l9hO; Steiner, 1939;
Winkler, 1939).
2) Tenderness is based-upon the swelling and
hydrolysis of collagenous tissue(Ramsbottom,
et al., 19h5; Lowe, l9h3; Ewell, l9h0; Anon.,
1939b; Moran and Smith, 1929).
Contrary to the findings of most investigators, Mohler(l939)
observed little difference in the palatability factors of high grade

beef either at 10 or 50 days storage(3h°F.).
Histological changes

The histological appearance of muscle has been studied extensively.

-7 -
Hewever, it has not been reviewed from the particular angle of quality
of meat, or the relation of the histological picture to tenderness or

toughness of muscle(che, 1932).

Paul, at al.(l9hh) found freshly killed beef fibers were poorly
differentiated, and straight to slightly wavy. After one day storage,
the fibers were more distinct, with contracture nodes, kinks and
crinkles. The nodes were still evident as late as 18 days storage,
but in feur to nine days the kinks and crinkles had disappeared. Normal
rigor produced more dense nodes than those caused by heat. Breaks or
disappearance of cross-striae appeared on the second day and increased
as storage time progressed. Two types of disintegration occurred:
sharp fractures across the fibers and disintegration areas within the
fibers. Paul, at al.(l9hh) found that cooking increased the micro-
scopic evidences of the rigor stages seen in the uncooked meat.
Harrison(l9h7) did not find that cooking intensified the microsc0pic
characteristics of the fibers. The semitendinosus muscle of beef
examined showed pronounced macroscOpic waves. These waves were present
fer four days but disappeared by the ninth day of storage. It was
postulated that the waves might be evidence of an appreciable amount

of elastin in the muscle.

Harrison(l9h7) feund the most outstanding characteristic of the
longissimus dorsi muscle to be the prominence of the longitudinal
striae in the fibers. Cross-striae of these fibers were evident only
under high power. Her conclusion.was that it was probable that histo-
logical structure of muscle fibers was related to tenderness of beef
since there was histological disintegration of the fibers during
aging at 3h.- 36°F.

Chemical changes

Chemical changes in fat during aging may be a limiting factor in

the storage life of chilled meat.

Oxidation of fat: In a series of studies on the chemical changes
in the fat of chilled beef, Lea(l931, 1933, 1935) followed the chemical

 

and palatability changes in beef fat stored in the chilled state for
various lengths of time. These experiments involved either: a) storage
at 0°C. for [:2 days, followed by hanging for four days at 10°C., or

b) storage at 0°C. for 60 days. In none of these experiments was atmos-
pheric oxidation of fat sufficient to render it unpalatable, if pre-
cautiom were taken against exposure to strong sunlight or artificial
light.

Free fatty acid: Lea(l931) found that wherever the unpleasant
flavor of taint occurred in fat, a correspondingly high value was always
found for free acidity(percent oleic acid). Although subsequent Low
Temperature Research Station investigations at Cambridge, England have
shown that free fatty acid is not itself responsible for taint, it was
suggested that free acidity might be taken as an index to the degree of
attack by microorganisms capable of splitting fats. Lea(1935) concluded
that the life of chilled beef, as determined by absence of unpleasant
taste in fat, was limited by the growth of microorganisms. Oxidation
(formation of peroxides) played a subsidiary, but still important part.
Moran(l929) agreed on these findings.

Scott and Vickery(1939) in the Australian investigations on chilled
beef found that a slight hydrolysis of fats occurred during chilling,
and that hydrolysis in loin fat was almost invariably greater than in
abdominal fat.

.9-
Both Lea(l939) and.fioran(l935) Stated that beef and mutton fats
were relatively resistant to oxidation except when frozen and stored
for long periods(longer than 18 months at -10°C.). Rockwood, et al.
(19h?) reported that free fatty acids and.peroxide values had a tendency

to increase with increasing storage time and temperature.

RE: The role of pH and its place in the aging of beef during
cold storage is a subject not yet clearly defined.

Bate-Smith(l9h8), Ramsbottom, et.al.(l9h5), Smorodintsev(l936),
and Moran(l935) all stated that the pH value of chilled beef muscle
averaged 5.6 to 5.7, and.might range from pH 5.3 to 7.0. Winkler(l939)
studied therelation between pH and tenderness and reported the maximum
toughness of beef occurred about pH 5.0. The pH at which maximum
toughness occurred was more variable between different animals in beef

than in pork.

Drosdov and Drosdov(l936) found that a rise in.pH to 6.2 - 6.3
was an early indication of decomposition. Harrison(l9h7) in her study
of aging in beef roasts concluded that there was an acidification of
beef’muscle postmortem. During storage at 3h - 36°F. the pH of uncooked

muscle decreased slightly and then slowly rose.

Bate-Smith(l9h8) in his comprehensive revieW'of beef muscle
activity and special consideration of the problem of ripening, stated,
"A.common factor in all aspects of the subject is the predominating
influence of the acidity of the flesh on its immediate prOperties and
future behavior. This influence is seen in the dependence of the
activity of the enzymes responsible for autolysis on pH, this factor

in turn, it is presumed, affecting the rate of increase in tenderness

during the ripening process."

- 10 -

Tenderness studies

Shear values: Several investigators have found a high correlation

 

between palatability tenderness and shear force(Mackintosh, et al., 1936;
Brady, 1937; Satorius and Child, 1938; Ramsbottom, et al.,l9h5). The

modified Warner—Bratzler shear apparatus(warner, 1928) has been generally
accepted as a reliable measure for the objective determination of tender—

ness in meat.

Tenderness variation: Ifiany authors have discussed the factors
that contribute to tenderness of beef’muscle. The sex, age, and grade
of the animal, size of the muscle fiber, amount of connective tissue
and amount of fat have all been studied in relation to tenderness. The
literature on these subjects has been reviewed by Bate-Smith(l9h8).

Tenderness differences of beef in cold storage between right and
left sides of the same animal have not been observed as long as comp
parable muscles were tested, nor were there observed differences in
tenderness from end to end of the longissimus dorsi muscle in the same
animal(Deatherage and Harsham, l9h7). However, Paul and Eratzler(19h9)
observed differences between adjacent steaks and between anterior and

posterior portions of the same muscle.

Ramsbottom,et al.(l9h5) in studying the comparative tenderness of
representative beef muscles stored at 3h.S°F., found.most.mmscles uniform
in tenderness throughout. However, the longissimus dorsi muscle was

somewhat less tender from posterior to anterior end of the muscle.
Cookinggstudies

McLachlan (1937) and Cline, et al.(l930) fbund that'the‘weight of

- 11 -
a steak determined the rate of cooking; the heavier the steak the
less time per pound required fer broiling. Total cooking time was
determined by'weight and thickness of the steak.

Tenderness in cooked meat is the total effect of aging before
cooking, heat coagulation of the nmscle fiber protein, and changes
which take place in connective tissue. Nbble, et al.(l93h) perform-
ing tenderness tests on cooked beef, found by means of the N.I.
Testing Laboratory Penetrometer that the difference between averages
of penetrometer values for corresponding right and left sides of
wholesale rib cuts were negligible when the cuts were treated in the

same manner.

Ramsbottom, et al.(l9h5) compared tenderness of 25 muscles from
each of three heifer carcasses. Tenderness was based on shear readings
before and after cooking the 25 muscles. The muscles were ranked
according to decreased tenderness in the raw samples. After cooking,
shear values showed that 17 of the 25 muscles decreased in tenderness,
four did not change significantly, and four became more tender. The
longissimus dorsi muscle was ranked as the fifth most tender muscle,
and showed a significant decrease in tenderness on cooking as indicated
by shear value. Similar findings were noted by Satorius and Child (1938)
in beef cooked to an internal temperature above 67°C. This decrease
'was attributed to the toughening effect of heat in coagulating and
hardening the muscle proteins. Coagulation caused the longissimus
dorsi muscle to become more tender up to 58°C. In a study made on
objective measurements for tenderness, Lowe(193h) found that longissimus
dorsi muscle cooked well done was less tender than uncooked muscle when

measured by penetrometer and shear stress apparatus. The difference in

e 12 -
the stage of coagulation of cooked muscle may have caused the dis-

crepancy in the results.

Increased internal temperature of muscle, prolonged storage
at 3h-- 36°F., and too lbw an initial cooking temperature of the
meat all brought about increased cooking losses as reported.by'Moran
and Smith(l929), Satorius and Child(l938), and Craghead(l938).

Freezing Storage Studies

Definition and purpose

Lean meat(muscle) contains 75 percent water. ‘When.musc1e begins
to freeze at -l°C., the water present is gradually converted to ice as
the temperature is reduced. In fresh meat this process is still not
quite complete at ~20°C. Separation of ice increases the hardness of
the frozen carcass. Meat held at -S°C. and below is usually referred
to as "frozen“, while at -2°C. and above it is classed as "chilled"
(Lea, 1939).

Freezing has long been believed to do “something” to meat. But
with limited information available on the subject, the effect of
freezing was generally regarded as unfavorable. The reputation of
frozen.meat was not good. It is only in recent years that more extensive
research has established the fact that, when preperly carried out,
freezing may be an asset(Hankins and Hiner, l9hh). One major benefit
indicated by recent studies on freezing appears to be a tenderizing
effect on beef. In general, the lower the freezing temperature the

greater the effect, according to these same workers.
Palatability changes

Major palatability factors involved in freezing meat are identical

, 13‘.
'with those of chilled beef: aroma, flavor, juiciness, texture and

tenderness.

Elgggr; Hankins and Hiner(19hl) stated that flavor of meat was
difficult to evaluate in frozen meat quality. However, in the few
studies mentioning flavor, the general consensus seemed to be that
flavor deteriorated in frozen storage(Lowe, l9h5). Off—flavor
deve10ped more rapidly when beef aged past the chill period was frozen
than when beef was frozen immediately after being chilled 2h.- hB hours
(Hiclonan, 19246). Tressler and Murray(l932) found sirloin steaks aged
four days at 33 — 37°F., then quick frozen and stored at 0°F. for one
month or longer, had better flavor than adjacent steaks aged at 33 -
37°F. for six to seven days and tested immediately without freezing.

Contamination and rancidity are probably the most common complaints

in the develOpment of off-flavors(Brady, l9h5).

Juiciness: Iowe(l9h5), Anon.(l9h6a), and Beard and Nelson(l9h0)
found that juiciness as well as flavor decreased in storage. McClurg
(l9h0) concluded that steaks frozen at 0°F. received a higher score

for juiciness than those frozen at ~lO°F.

General palatability: Brady, et al.(l9h2) determined the effect
of freezing rate on the quality of two pairs of U.S. Commercial beef
rounds. No significant difference was found between steaks quick
frozen(-15°F.) and slow frozen(0°F.) with respect to palatability
scores. Ebard and Nelson(l9h0) reported that palatability was little
affected by temperature or period of freezing when roasts and steaks
‘were frozen at 0°F. and - 0°F. and stored fer periods of 30, 60, 90,
120, 2h0, and 365 days before examination. Child and Paul(l937) found
palatability of beef was unaffected by freezing and by use of different

-m-

thawing temperatures. Artyokh(l9h0) presents similar results.

Tenderness: Tenderness is generally recognized as one of the

 

most important characteristics of meat. "When meat has a low degree
of tenderness, to many peOple it is quite unsatisfactory, although it
may be thoroughly desirable with respect to other characteristics.

Therefore, any factor that has an effect on tenderness is of definite

concern to the consuming public" (Hankins and Hiner, 19b0).

Three approaches have been made to the study of tenderness and
freezing of beef: 1) influence of low temperatures; 2) the effect of
length of frozen storage; and 3) the effect of aging and subsequent

freezing.

In a study on six Hereford steers, Bray, et al.(l9h2) indicated
that little or no change in tenderness of aged beef was due to freez-
ing. This is contrary to other findings in later studies.

AHankins and Hiner(l9h0, 19hl) found that freezing appeared to
make meat more tender. Four pairs of beef shortloins were stored 96
hours at 3h°F. They were then cut into steaks and frozen at -6.7°C.
(20°F. ), ~23.3°C.(-10°F.) and ~ho°c.(-ho°F.). A control was held at
3h°F. the steaks frozen at the two lower temperatures were more tender
than those frOZen at 20°F., and showed a definite increase in tenderness

over the unfrozen steaks.

The effect of length of frozen storage time and influence of low
temperatures upon beef was investigated by Miller, et al.(19h7) and
Beard and Nelson(l9h0). The steaks from beef shortloins were frozen
at -10° and 0°F. and held in storage at 0, l0 and 15°F. Miller and
his associates found that freezing at -8°F. and storing at 0°F. in-

.. 15 -
creased tenderness. Beard and Nelson concluded that tenderness
increased during the first 120 days of storage and then remained
constant.

McClurg(19luO) presented the following results on tenderness
from his study on steaks and beef roasts held in storage at subfreezing
tenmeratures. The roasts frazen at ~10°F. were more tender than the
roasts frozen at 0°F. However, these results did not apply to the
steaks in the study. The major changes noted in the steaks were
evident in other palatability scores.

Several large studies have been made on tenderness of beef as
affected by aging with subsequent freezing. Hiner and Rankine (19h7,
191th, 19141) aged beef short loins five days at 3h°F. and froze them
in still air at +18, 0, --18, 440, and -llh°F. The samples were thawed
at h5°F. and cooked to 138°F. internal temperature in an electric oven.
Cooked santples were tested for tenderness by shear cores. Samples
frozen at +18°F. were more tender than the unfrozen sample; while beef
frozen at -1lh°F. was the most tender. At temperatures between -18°F.
and -llh°F. tenderness was intermediate, increasing with decreasing
freezing temperatures. Similar results have been presented from other
studies using different aging and freezing tauperatures(Anon., l9h6b;
Brady, 191:5; Tressler and Murray, 1932; Miller, et al., 19147).

Miller, et al. (19h?) and Tressler and Murray(l932) noted that
lower grades of steaks diaplayed a more pronounced tendering effect
than tap grade steaks. Tressler found Grade C sirloin steaks after
five weeks of aging plus quick freezing, as tender as Grade A steaks
prior to freezing. He concluded that the process of tenderizing
quick frozen meat continued during frozen storage.

- 16 -
Herne(l937) questioned the reasons for increased tenderness in
quick frozen meat. It was his belief that tenderizing of meat was an
enzymatic process. This process had been shown to proceed more rapidly
at high temperatures than at low temperatures. Tressler and.Murray(l932),
in agreement with other investigators, acknowledged the fact that tender-
izing of beef at temperatures above freezing was brought about by the
action of enzymes contained in the tissues. They also pointed out that
such activity continued, but at a greatly reduced rate, at temperatures
slightly below freezing and more slowly as the freezing temperature was
lowered. In addition, Tressler remarked that hammering of meat changed
it physically so that it was more easily masticsted. Presumably'quick
freezing acted in a somewhat similar physical manner in conjunction with

continued slow enzyme activity to increase tenderness in meat.
Histological changes

Microscopic or histological approach to the effect of freezing on
beef has been entirely from.the viewpoint of ice crystal formation.

Richardson and Scherubel(l908) examined longitudinal and cross-
sections from frozen beef knuckle histologically as an aid in determining
the deterioration of flesh foods. Ice crystal formation indicated the
effect of fast and slow thawing on the tissue. They concluded that the I
slow thawing produced nearly normal tissue while tissue thawed rapidly
at high temperature showed distortion of fibers.

Beard and Nelson(l9h0) stated that the microsc0pic structure of
frozen meann was similar under the influence of both 0°and -10°F.
freezing temperatures and holding for various storage intervals. 'Where
freezing was delayed in the deep layers, the crystal size of the ice

increased.

.. 17 ..

A series of studies by Hiner and Hankins(19h7, 19146) and Hiner,
et al. (1916). with reference to the effect of temperature of freezing
on histological characteristics of longissimus dorsi muscle, brought
forth the following conclusions :

Sections from muscle frozen at 18°F. showed large
interfibrillar ice crystals which had pushed the
fibers into distorted groups. No intrafibrillar
ice crystals were visible. As freezing temperatures
were lowered, ice crystals became smaller and more
numerous. The first intrafibrillar ice was visible
as the result of 0°F. freezing. Fiber splitting
was observed in longitudinal sections at -10°F.,

and became more and more extensive as freezing
temperatures were lowered to -1lh°F.

A series of longitudinal and cross-section samples
were sectioned at 25 mm. intervals from the emosed
surface to the center of the round, a distance of
approximately 150 mm. Photomicrographs showed the
largest crystals were near the surface and smaller
more numerous crystals near the center. This was
true for each temperature studied. In general,
crystals in rounds frozen at 18°F. were larger than
those frozen at 0°F., and so forth for decreasing
temperatures. No fiber splitting or intrafibrillar
ice crystals were observed in rounds frozen at 18°F. *
At lower freezing temperatures, fiber splitting was
found in longitudinal sections, and became increas-
ingly extensive as temperatures were lowered to the
extreme of -llh°F.

Hiner, et al.(l9h5) observed that, as freezing temperatures were
lowered, the fibers became more nearly paralle1(less bunched) and were

fewer per group.

Hiner and Hankins(l9h7) believe that the increase in tenderness
observed in freezing beef was probably due to increased fiber rupture
by intrafiber ice formation, and stretching and rupturing of inter-
stitial connective tissue.

Chemical 011393893

The development of rancidity in fat tissue has been shown to have
considerable influence over the storage life of chilled meat(Lea, 1931 ).
The keeping quality of fat tissue in frozen storage is not much improved

-18-

over that found in fat tissue maintained in cold storage.

Kiermeier and Heiss(l939) stored beef quarters and half pork
carcasses up to 18 months at -8.5, -15, and -21°C. to ascertain the
keeping quality of beef and pork fat at low temperatures. The higher
storage temperatures were unsatisfactory for periods of even five
months, since the fat tissues became rancid; -21°C. was the preferred
storage temperature for the product, as the odor at this temperature
was better after one year's storage than at the higher temperatures.
These men concluded that for long periods of storage, fat tissues
should not be Subjected to air currents, as the fat becomes rancid
more rapidly. Peroxide and aldehyde values increased in the presence
of atmoSpheric oxygen. Storp(1913) found fatty tissues of frozen

meat suffered no appreciable change in two months storage.

Brady(l9h5) remarked that meat stored for long periods in the
frozen state became subject to rancidity develOpment. This development
‘was progressive and resulted in a marked diminution of palatability of
ithe product. He attributed this rancidity to 1) the atmospheric
oxidation of unsaturated fats and subsequent development of offeflavor
and aroma; 2) the action of microorganisms which.result in extensive
hydrolysis accompanied by unpleasantly flavored metabolic products;

3) the presence of tissue enzymes which led to deveIOpment of free
' acidity; h) picking up of objectionable fereign flavors. Brady con?
cluded that temperature, length of storage, and previous handling all

appeared to have a very important effect on the develOpment of rancidity.

Ramsbottom(l9h7) found that frozen beef, lamb, and pork stored at

—10 F., for a period of seven years,was markedly changed in appearance

- 19 -
and flavor of the fatty tissue. After a storage period of one year,
there was no significant change in the free fatty acid content of
chOps. However, the development of peroxides in the fat was a function
of time and temperature. Brady(l9h5), Shrewsbury, et al.(l9h5) and
McClurg(l9h0) revealed similar findings. Hankins and Hiner(l9hl)
reported little difference in free fatty acid content between freezer-
stored.meat samples previously chilled at 33°F. and 50°F.

Most investigators of the keeping quality of fat in.meat have
agreed that beef and lamb fats are more resistant than pork fat to
oxidative changes(Moran, 1929; Rankine and Hiner, l9hl; Lea, 1939).

pH: In similar studies conducted at a six—year interval,

Ramsbottom(l9h7) and Ramsbottom and Koonz(l9h1) found no significant
change in the pH of'beef stored for one year at -10°C. to -30°C. The
pH values were given as 5.h to 6.2, and it was suggested that there
was no real relationship between storage condition and pH; McClurg
(l9h0), however, found the difference in pH values between storage
periods fer steaks were highly significant. Steaks stored at -lO°F.
were more acid than those stored at zero or 15°F. Both steaks and

roasts were more acid after 365 days storage than after 30 days storage.

Beard and Nelson(l9h0) found the pH value of frozen beef held in
storage for different intervals dropped from.6.2 to 5.7 in a 60 to 90
day period; then suddenly rose to 6.6 on the 120th day; McClurg(l9h0)
noted the same rise in alkalinity at 120 to 250 days frozen storage.

Heiss(l936) stated that the pH value influenced freezing altera-
tions in meat and that oxidative changes were accelerated by decreasing
pH values. He suggested that freezing of meats should take place as

soon as possible after the kill to prevent pH reactions.

- 20 _
Tenderness studies

Shear value: Samples of beef from several freezing studies have

 

shown a decrease in shear values which represented an increase in

tenderness of the meat.

Rankins and Hiner(l9h0) reported that steaks held at 3h9F. had
higher shear strength and were less tender than steaks frozen at 20,
—10, or -bO°F. Steaks frozen at 20°F..showed a 12 percent decrease in
shear value below the steaks held at BupF. The -lO°F. and ~h00F.
samples each showed an 18 percent decrease in shear below the unfrozen
steaks. The shear values for each animal reflected the variability
within each carcass. .A similar study made in 19h1 by these same men
indicated that length as well as temperature of storage was reflected
in a decrease in shear values for frozen short loin steaks.

In 19hl and 19hh, Rankine and Hiner concluded that the most
rapid tenderizing effect on longissimus dorsi steaks occurred during
the first 15 days of storage at BhQF. when the shear value at five days
was 25.8, and at 15 days 20.7. Aging for 15 days at 3h9F. fellowed by
freezing at -lO°F. produced the most tender product.

Tenderness variations: Steiner(l9hl) Pointed out that the age
and sex.of the animal as well as other factors affect the speed of
aging of beef'mmscle during frozen storage. As in normal aging,
toughness increased at first, then decreased to a point under the
initial value.

Bray and cadworkers(l9h2) found indications that the change in
toughness of aged beef'might vary with the animal. Considerable variation
was found between animals. The posterior section of the short loin
was noted to be more tender than the anterior section. Bankins and

v 21 -
Hiner(19h0) and.Miller, et al.(l9h7) drew the same conclusions.

Bray, et al.(l9h2) found considerable variation among the cores
taken from.the longissimus dorsi muscle, the greatest variation
occurred in the lateral core. These investigators also found the
right side of the animal to be significantly more tender than the
‘left side. Hankins and Hiner(19h0) and others have shown there were
no important differences between left and right sides of’carcasses
in their studies.

Cookinggstudies

Tenderness in cooked, frozen meat covers the some factors

involved in chilled, cooked beef.

McClurg(l9h0) in a study on quality and palatability of beef
after storage in sub-freezing temperatures, fibund that cooking losses

decreased as storage losses increased.

Brady(l9h5) and Brady, et al.(l9h2) concluded that steaks cooked
from.the frozen state had a smaller cooking loss than when thawed
first. But palatability scores were not significantly different on
either method of thawing.

EXPERJIENTAL PROCEDURE -

Description of meat

The longissimus dorsi muscles from both the right and left sides
of two beef animals were obtained immediately after slaughter from the
Animal Husbandry Department. Animal I was a four-year old Shorthorn
cow and Animal II was a two-year old Shorthorn heifer. Both animals
were U.S. Commercial grade.

Preparation of samples

 

Each muscle was divided into 214 one-inch steaks. These were
numbered from the posterior or sirloin end to the anterior or rib end
of the muscle as shown in Figure 1, page 23. The following table was
set up for determining methods of treatment and for analysis of the data.

Table l. A summary of aging and storage treatments on steaks for
Animal I and Animal II

 

 

Aged hours Samples
Treatment at OF. Animal I 1115111211 II
Unfrozen O )4 steaks-If h steaks*
5 I! u I! u
2h :1 u u u
167 I! II N I!
Frozen - 1 week 0 14 steaks* h steaks-'1'
5 ‘3 II II 3!
2h 1: u n n
167 u u :1 fl
Frozen — )4 months 0 h steaks'K- )4 steaks-K-
" II I! ll
2?; :3 ll 3| I!
167 H II N I.

 

i I; steaks from each arfimal as follows:
2 pairs (left and right): 1 steak of each pair for palatability scores
1 steak of each pair for other analyses

- 23 -

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mm

m

 

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w

 

mm;

 

L

sothmm,om

 

 

 

J.

 

 

m

 

m

 

0H

 

 

NH

 

_--— -— -

 

vH

 

 

 

mH

donned ea

 

 

 

 

5H

dew

 

Iwhoaumpnd

 

ma

mH

 

 

V

C

 

ON

meadow nematode em opmfi saunas “mace mdsammamooa mo soamfi>ae Mo asumsfin

 

aw mm mm—mWV

 

.H madman

.. 2h _.
The cold storage periods employed for the 96 steaks were 0,
5, 211, and 167 hours at 1:601? . Iielve steaks from each animal were
aged at each cold storage period, (Table 1, page 22). At the end of
each holding period the 12 steaks received the following treatment:
1) Four steaks. (2 left and 2 right) were removed
from the refrigerator and cooked immediately
for palatability and tenderness scores.

2) Four steaks (2 left and 2 right) were frozen
at -26°C. (-150F.) and stored for one week at 0°F.

3) Four steaks (2 left and 2 right) were frozen

at -26°C.(-15°F.) and stored for four months

at 0°F.
The steaks for freezing were wrapped with a drugstore wrap in cello-
phane (MEAT 300), sealed with transparent tape, labeled, and frozen.
Capper-constantan thermocouples connected to a Brown Electronik Record-
ing Potentiometer recorded the rate of freezing for one pair of steaks
from each group. The freezing curves are shown in Figure 2, page 25.

The frozen steaks were over-wrapped with stockinette, tied
securely at each end. The one week storage samples were held in a deep-
freeze box; the four months storage samples were packed in a corrugated
paper carton, sealed, and placed in a comercial locker plant.

At the end of their respective frozen storage periods, the steaks
were removed from the stockinette wrapper and placed on the bottom shelf
of the laboratory refrigerator to thaw. This required approximately 16
hours at h6°F.

llethod of cooking
Each steak was weighed on removal from the refrigerator. The two

pair of steaks from each set of four (left and right) were then handled
in the following manner: one steak of each pair was tested organo-
leptically; the second steak of each pair was divided as follows: a
portion of the lean was reserved for pH determination, the raw fat set

-25..

Figure 2. Freezing curves for longissimus dorsi
steaks aged at h6°F. prior to freezing

 

 

1,2 - aged 0 hours h6°F.
33h "' aged 5 hours ’46017.
5 6 - aged 21: hours 1:601“.
7,6 - aged 16? hours h6°F.

 

 

 

— 26--
aside for peroxide and free fatty acid analyses, and the remainder of
the lean cooked for shear tests.

Thermometers were inserted into the thickest portion of lean
tissue to record internal temperatures of each steak before and during
cooking, and maximum.temperature reached after cooking. All steaks
'were deep-fat fried in vegetable shortening at a temperature of 150°C.
(302°F.) to an internal temperature of 63°C.(lh5.h°F.)(medium rare).

On removal from the fryer, each steak was drained for 30 seconds per
side on brown.paper toweling to remove excess fat, and allowed to come
to maximum.temperature at which time the cooked weight was recorded.

Data recorded for each steak were: 'weight before cooking, weight
after cooking, cooking time, temperature before cooking, internal cook-
ing temperature, maximum.internal temperature after cooking, cooking
loss in grams, and percent cooking loss.

Palatability;§cores

 

A panel of five experienced judges from the Foods and Nutrition
Department scored the cooked steaks for appearance, aroma, flavor of
fat.and lean, juiciness, tenderness, texture,and general conclusion.
Any comments the judges wiShed to make on the steaks were recorded. A
possible high score of seven and a low score of one covered the range
for each factor. A sample score sheet is shown on page 67 in the
appendix.

Each steak was cut into five one-inch strips the width of the
steak with the grain. The judges scored strips from the same position
in each steak at each taste period. A piece of fat was included in
each strip wherever possible so that the flavor of both the fat and
(the lean could be tested. All steaks were coded for impartial judging
by the panel, and from.two to four steaks representing both left and

right sides of the animal were scored at one time. Glasses of cold

.. 27 ..
water were provided each judge. The 0, 214, and 167-hour samples from
each treatment were scored at 10:30 A.l[., and the 5-hour samples for
each treatment at 2:30 P.M.
ace

Seven cylindrical cores one-half inch in diameter were taken from
one left and one right steak in each group at each scoring period.
Cores were sheared on a modified Warner-Bratzler shear stress apparatus.
The seven readings from each steak were averaged.

Chemical methods

 

p_H_: .A five gram sample of raw lean tissue was minced with a sharp
knife, mixed with ’45 ml. of distilled water, and allowed to stand 20
minutes. The liquid portion was decanted and the pH of the liquid de-
termined by a Beckman pH meter. Duplicate readings were made on each
steak.

Peroxide number: Determinations of the peroxide number of the raw
fat were made by a slight modification of the method described by Watts
(19147). The original method was adapted to the problem of raw fat .
analysis by substituting two grams of minced raw fat plus four grams of
anhydrous sodium sulfate for 25 grams of pork sausage meat and 50 grams
of anhydrous sodium sulfate. The remainder of the Watts procedure was
not altered. Duplicate determinations were made on each sample. Rock-
wood, et al. (19h?) followed essentially the same procedure in determining
peroxides in fresh pork loin fat.

Free fatty acid: Free fatty acid content of the raw fat was
determined from a portion of the sample used for determining the
peroxide number. The method described by Halliday and Nob1e(19h3) was
used. Duplicate determinations were made on each sample.

Histological studies

 

Histological studies were made to determine the changes in the

.. 28. ..

muscle fibers during both cold storage and freezing storage of the
steaks. Samples from both the raw and cooked meat were preserved,
in 10 percent formalin and were later embedded in gelatin. The em-
bedded samples were frozen with carbon dionde, and longitudinal
sections cut 10 to 15 microns thick on a Spencer Freezing Microtome.
The sections were stained with Harris hematoxylin and mounted in
glycerine jelly. This treatment yielded blue muscle fibers while
the gelatin frame was a pale blue.
Statistical methods

Correlation coefficients were calculated, and analysis of
variance made, according to the methods recommended by Snedecor(19h6).

DISCUSSION OF RESULTS
Palatability Changes

Definition of terms

Cold storage in this studyr prefers to the holding of fresh beef
at the temperature of 146°F. Frozen storage refers to steaks frozen
at -26°C.(-15°F.) and held in storage at 0°F. {for periods of one week
or four months. "Aging" or "aging period", refers to the 0, 5, 2b,
and 167-hour time intervals that the steaks were held at h6°F. Treat-
ment applies to frozen steaks in contrast to unfrozen steaks.

Appearance

Little or no difference in scores for appearance of the steaks
(Table 2.) resulted from cold storage or frozen storage treatment of
the Steaks.

Table 2. Mean scores for appearance of longissimus dorsi steaks
in cold storage and frozen storage

 

 

Aged, hours fil'reatment
at h6°F. Unfrozen Frozen - 1 week Frozen - 1; months
0 5-7 5.5 5-7
215; g? 3?! fig
167 5:6 5:6 5:5

 

The judges described the frozen storage steaks for both storage times
as dark and dry on the surface.

Aroma

The aroma of the steaks(Table 3, page 30) appeared to increase
slightly during aging. The aroma score increased within each treatment,

.. 3o ..
becoming more desirable with frozen storage. Ramsbottom(l9h7) found
aroma of steaks did not deteriorate unless held in frozen storage at
~10°C. or lower for long periods of time.

Table 3. Mean scores for aroma of longissimus dorsi steaks
in cold storage and frozen storage

 

 

 

Aged, hours Effluent
at 146°F. Unfrozen Frozen - 1 week Frozen - 1; months
0 502 50h 50,4
5 5.2 5.7 5.1
2h 5.0 5.5 5-9
167 5024 508 5.9
Flavor

_I£a_r_1: The flavor score for lean tissue increased slightly at
167 hours aging in cold storage(Table 14.). The set of four steaks
aged 0, 5, 21;, and 167 hours, and subsequently held in frozen storage
for one week at 0°F., followed the same trend of increasing flavor

Table )4. Mean scores for flavor of lean of longissimus dorsi steaks
in cold storage and frozen storage

 

 

Aged, hours _ 1I‘IETEatment '
at héoF. Unfrozen Frozen - 1 week Frozen - )4 months
0 14.7 14.6 5.1
.5 t2 a»; a
167 5:2 <5I1 5:2

 

score as the cold storage steaks. The steaks held in frozen storage
four months at 0°F. show little change resulting from the four aging
periods within the treatment. But the increased length of frozen

storage appeared to develop a flavor in the lean tissue slightly more
desirable than that found in either the steaks held in frozen storage

-31..

one week or in cold storage.

One judge consistently commented on a metallic flavor in the
lean tissue. "Indistinct" and “lack of flavor" were comments made
on the unfrozen and froaen for one week samples. Beard and Nelson
(1910) stated that the flavor of lean beef tissue in steaks did not
appear to be noticeably affected by low temperature storage(0 and
-—lO°F. ) except at periods beyond 120 days.

333: The flavor scores for fat on the longissimus dorsi steaks
remained unchanged in cold storage, but increased in desirability in
both frozen storage periods; however, the trend of the scores was
different within each of the frozen storage periods(Table S). The
score for flavor of fat decreased in value for 167 hours aging and

Table 5. Mean scores for flavor of fat of longissimus dorsi steaks
in cold storage and frozen storage

 

 

lged Tours 1Itreatment *—
at [1601“. Unfrozen Frozen - 1 week Frozen - 1; months
0 hos ho3 5.3
5 ho6 h-9 5.2
21: ms h.6 [5:3
167 14.5 i0 .9

 

freezing for four months. This lessened desirability of the fat flavor
in the latter part of the four-months frozen storage period may be
indicative of develOpment of incipient rancidity in the fat.

Texture

Texture scores(Table 6, page 32) showed considerable variation
within treatments. In unfrozen storage, the scores drOpped consistently
from O to 5 hours, and from S to 21; hours aging, but increased again to

the original score after 167 hours aging. The scores for the group

Table 6. Mean scores for texture of longissimus dorsi steaks '
in cold storage and frozen storage

 

 

Tgecf hours fiea'hnent
at L60F. Unfrozen Frozen - 1 week Frozen - LLmonths
o h.h h.2 3.2
S 3.6 3.8 3.1
2’. 3.3 h-O 3.14.
167 m5 luS h-l

 

of steaks frozen one week fluctuated for the first three periods within

the group, but increased at the 167-hour period to equal the comparable

score(167 hours) in the cold storage group. The scores for four months

frozen storage were the lowest of the three storage periods, but again,

the last aging period within the group showed improvement over the three
earlier periods in the same group. The judges commented on the stringy

texture of the steaks throughout the test period.

The texture scores in cold storage and four months frozen storage
appeared to follow the same pattern as the tenderness scores. Brady
(1937) found that texture of longissimus dorsi beef muscles aged 10
~ days gave a high positive correlation with tenderness scores.

Tenderness

In Table 7, page 33, the tenderness scores were the most variable
of any of the individual palatability factors. The unfrozen steaks
were quite tender at zero storage time, but decreased sharply in tender-
ness during the next 2).; hours of cold storage. By the time 167 hours
of aging had been completed, the steaks had again increased in tenderness

to a score comparable to the tenderness score of the zero storage sample.

- 33 -
This tenderness pattern is believed to parallel onset and height
of rigor mortis in the meat within the first 2h.hours after slaughter
of the animals, and the dissolution of rigor after 167 hours aging

Table 7. Mean scores for tenderness of longissimus dorsi steaks
in cold storage and frozen storage

 

 

Aged ’hours Treatment
at 36°F. Unfrozen Frozen - 1 week Frozen - h.months
0 h.0 2.8 2.5
E 2.9 2.8 2.3
2 2.2 3.5 3.1
167 h.1 h.5 h.0

 

at temperatures above freezing(h6°Fo)o

The tenderness of the steaks held in frozen.storage fer one
week at 0°F. presented a different pattern from.that found in the
cold storage group. The mean scores for the 0 and 5-hour samples
in this group were comparable to the 5-hour samples held unfrozen.
The 2b and 167-hour samples in one week frozen storage showed increased
tenderness scores over the zero and 5-hour samples within the same
treatment. The 167-hour sample scored the most tender and surpassed
the tenderness rating of the comparable steak in the cold storage
group.

The four months' frozen storage steaks presented a tenderness
pattern which.paralleled the samples frozen for one week. But all
values were consistently lower throughout this storage period. The
zero and 5-hour samples in extended frozen storage had tenderness
scores comparable with the 2hrhour cold storage sample. These were
the lowest tenderness scores received in the study. The 2h and 167-

hour samples frozen four months were more tender than the steaks

- 3h -
tested at the early aging periods receiving the same treatment. The
167-hour sample was comparable in tenderness value to the O and 167-
hour unfrozen samples.

The steaks held in frozen storage for four months had apparently
reached the same degree of toughness in the O and 5-hour samples as
the 2h~hour sample held in cold storage. This comparable degree of
toughness in the two treatments at different aging periods would indicate
that the process of aging found in cold storage samples is continued in
the frozen meat. Freezing storage periods intermediate between one
week and four months would probably clarify the pattern of tenderness

deve10pment in frozen storage.

The judges commented on the lack of tenderness in the steaks
throughout the study, particularly where the lowest tenderness scores

are shown.

Extensive work by several investigators(Hankins and Hiner, l9h7;
l9hh; 19hl; Miller, at al., 19h7; and Tressler and Murray, 1932) has
shown that the freezing of meat makes it more tender. This study has
shown a definite increase in tenderness in frozen storage at the 2hr
hour cold storage interval, a slight increase in tenderness during
freezing at the 167-hour period, but a decided decrease in tenderness
at the 0 and 5-hour aging periods. Extended frozen storage treatment
did not increase the tenderness of the steaks in this study; one week
frozen storage showed tenderness improvement in the two later aging
periods.

Gortner(l9h8) suggested that the tenderizing action of freezing
could take over at least a part of the functions of aging. He stated

that where meat was to be frozen, the aging period could be shortened by

.. 35 ..
approximately 50 percent, with resultant increased storage life,

decreased shrinkage from moisture loss, and reduced trimming losses.

Tenderness is considered to be one of the more important
palatability factors in meat, and one greatly influenced by cold
storage and frozen storage treatment. Therefore, a statistical
analysis of the tenderness data was made to separate variation due to
animals, treatment, hours of aging and sides of animals. Table 8,
gives the F values which were found to be significant.

Table 8. Sigificant F values from analysis of variance of
tenderness scores

 

 

Source of variation F values
Animals 50.13%)?
Hours 36.07%
Animals 1 treatment 10.13*
Animals 1: hours 5. b7*
Treatment 3: hours 9. 53“

Animals x treatment 3: hours 7.67%
see p, less than 0.01
* p, less than 0.05, greater than 0.01

 

The F values show that the differences due to animals and hours
of aging were highly significant. Differences between animals are
usually attributed to biological and management variations, which
could not be controlled in this experiment. The differences due to
hours of aging are considered to arise from the onset, height and

dissolution of rigor in the muscle after slaughter.

The interaction between treatment an hours was highly significant,
indicating that the rate of change in tenderness due to aging was
altered by frozen storage. The interactions between animals 3: treatment,

- 36 -
animals x hours, and animals x treatment x hours were significant, showh
ing that there were differences between.the two animals used in rate of

change of tenderness due to cold storage and frozen storage.

Juiciness

Juiciness scores revealed little effect from treatment, but some

effect from aging(Table 9). Several investigators have reported that

Table 9. Mean scores for juiciness of longissimus dorsi steaks
in cold storage and frozen storage

 

 

Aged,lhours Treatment
at h6°F. Unfrozen Frozen — 1 week Frozen - h.months
0 5.0 h.9 5.1
S ho9 ‘ Sch 5-1
2h 5.3 5.0 5.1
167 j.3 5.1 5.2

 

juiciness scores increased with aging. The scores in this study were
found to increase in the latter periods of cold storage and in one
instance in frozen storage for one week. The average juiciness score
for each treatment was the same(5.1). If the frozen storage were ex-
tended.beyond the four months period, it might have shown more effect
on this palatability factor. The judges commented that the cooked
steaks from.both frozen storage periods were "dry".

General conclusion

 

Palatability scores for general conclusion paralleled the tenderb
ness scores for all three storage periods(Table 10, page 37). The
average scores for each treatment were higher than the tenderness scores

for these periods.

The general conclusion scores were analyzed to separate the

- 37 -

Table 10. Mean scores for general conclusion of longissimus dorsi steaks
in cold storage and frozen storage

 

 

Aged, hours Treatment
at h6°F.~ Unfrozen Frozen - 1 week Frozen - h.mcnths~v
0 h.3 3.E 3.2
E 3.6 3. 3.2
2 3-1 3.9 3.5
167 h.6 h.7 h.2

 

variations due to animals, treatment, hours of aging and sides of
animals. Table 11, gives the F values for the factors found to be
significant.

Table 11. Significant F'values from.analysis of variance of
general conclusion scores

 

 

Source of variation F values
Animals 33.88**
Treatment 10.13*
Heurs 38,13**
Animals x treatment 12.5o**
Animals x.hours 5.38*
Animals 1 sides 7,63*
Treatment x.hours 7.00%
Animals x treatment x hours 7.75%

 

Aiirp,‘1ess—than.0.01_
* p, less than 0.05, greater than 0.01

The differences due to animals and hours of aging'were highly
significant, probably for the same reasons given under the discussion
of tenderness scores: the biological and.management variations between
animals and the changes in tenderness generally considered to be assoc-
iated with the onset and dissolution of rigor. The most noticeable
differences feund within each treatment were for zero aging and for
2hphour aging periods. At zero aging the cold storage sample was
superior, at 2hphours aging, it was least desirable. The general con-

- 38 -
c1usior1scores reflect the collective influence of the other palatability
factors: the scores for appearance, aroma and juiciness were quite
uniform throughout the study, the flavor scores for fat and lean in-
creased slightly, but the tenderness and texture scores were variable.
The tenderness scores appeared to have the greatest influence on the
general conclusion scores as determined by the taste panel, since there
'was a similar trend for these two factors through each storage period

and each aging period.

The interaction between animals x treatment was highly signif-
icant; significant interactions were found for animals.x hours,
animals x sides, treatment x hours, and animals x treatment x hours.
These indicate that the differences between the two animals affected

the general conclusion scores as well as the tenderness scores.
Shear Keasurements

The relative tenderness of the cooked steaks was evaluated by
shear force determinations. Correlation coefficients between shear
force readings and the scores on tenderness and texture of the cooked
steaks were calculated. These are given in Table. 12.

Table 12. Correlation coefficients between shear ferce readings and
judges' scores on tenderness and texture of cooked steaks

 

Number of pairs (be‘fficlent of

 

Correlation between of samples correlation,_r
Shear force and tenderness

score DB -.768**
Shear force and texture score h8 -.5h7*

 

** p, less than 0.01
* p, less than 0.05, greater than 0.01

- 39 _

A highly significant correlation was found between the judges'
scores for tenderness and the shear force values for the steaks, and
a significant correlation between texture scores and shear values.

The correlation.coefficients were negative because the more tender the
meat, the higher the judges' scores, but the lower the shear force
value. Similar results have been reported by other investigators
(Ramsbottonn, et al., 1915; Satorius and Child, 1938; needy, 1937;
iackintosh, et al., 1936).

The significant correlation coefficient obtained between shear
value and texture score appears to lend further support to the tenet
that texture and tenderness in the longissimus dorsi muscle might be

directly related, as reported by Erady(l937).
Cooking Changes

The data on the cooking losses of the steaks are presented in
Table 13, page to. The average values indicated that freezing and
storage did not appreciably effect the percentage of total cooking
losses. The average percentage of losses for the cold storage steaks
was somewhat less than for the steaks which.were frozen and held in
frozen storage. However, the average total cooking time was also less
for the unfrozen than for the frozen steaks. The lower cooking losses
for the unfrozen steaks were probably due to the shorter cooking time,
which might be attributed to the higher initial temperature of the cold
storage steaks when they entered the deep-fat fryer. Their average
initial temperature was 21°C., while the average initial temperature
of the steaks which had been frozen and thawed was 10°C., lower than

- ho -

Table 13. Summary of averages of combined weights of longissimus
dorsi steaks, of cooking time, and cooking losses
from.Animal I and Animal II

 

 

Aged,—hours Wgt. of cooking ‘Percent cooking losses

 

Treatment at h60F. steaks time total loss per
g. min. loss_¥ min.
Unfrozen 0 189.2 3.0 17.96 5.99
5 192.9 3.9 18.72 b.80
2h 193.6 h.2 23.52 5.60
1o7 l8h.5 h.2 22.77 S-h2
Frozen- 1 week 0 190.7 h.2 23.96 5.70
5 189.1 h.0 23.52 5.88
2h 187.1 5.h 27.22 5.0h
167 213.9 6.7 30.07 u.h9
Frozen-h.months 0 165.h 3.5 2h.33 6.95
5 198.6 5.h 25.00 h.63
2h 19).»? 3.9 25-h8 6.53
167 172-5 be? 25-05 5°33

 

_ m ..

that of the unfrozen steaks immediately before cooking. The coefficient
of correlation(r, 0.713) between total cooking time and percentage of
cooking losses was highly significant. This would indicate that the
increased losses in the frozen steaks were closely related to the longer
cooking time. When the data were calculated on the basis of percent
cooking loss per minute cooking time, all three treatments gave similar
results which did not appear to be influenced by either storage time

or storage temperature.

Chemical Changes

Peroxide values of fat
Table 114, page ’42. presents the peroxide values for the raw fat

from the samples in cold storage and frozen storage.

It is generally considered that the peroxide values must be
greater than 10 milliequivalents per kilogram of fat before obvious
rancidity is indicated(Watts, 19M). None of the values found in
this study approached this value. This agrees with Storp's results
(1913 ). He found that fatty tissues of frozen meat showed no appreciable
change in peroxide value in two month's storage. The values for each
animal within each treatment were variable and did not appear to be
greatly influenced by the aging time. Animal II showed a more definite
trend toward increase in peroxide values than Animal I.

The average values of the combined data for both animals for
each storage condition reflected an increase in peroxide values in
one week frozen storage over the cold storage samples, but a decrease
in values for the fats held in frozen storage for four months. The
apparent decrease in peroxide values at four months frozen storage may
reflect a decomposition of peroxide at a rate more rapid than its
formation. The higher peroxide values for Animal II at the 167-hour

Table 1h. Peroxide values of unfrozen and frozen rfw fat from
longissimus dorsi muscle of beef

Milliequivalents_per kilogram.of fat

 

 

Aged, Edurs
Treatment at héoF. Animal I Animal II
Unfrozen 0 2.95 2.53
5 3.35 2.92
2h h.18 2.17
167 2.5h 3.h6
Mean values 3.26 2.77
Frozen - 1 week 0 2.55 3.8h
5 2.35 3.77
167 2.82 5.h5
Mean values .2.h2 h.20
Frozen - h.months 0 2.66 3.01
S 1.39 2.02
2b 1.73 3.27
167 2.03 5.37
_ Mean values 1.95 3.h2

 

1

Figures are averages for two steaks(right and left sides)

from longissimus dorsi muscle from each animal

-10..
aging period in both one week and four months frozen storage might
indicate development of incipient rancidity. There was also an
indication of this in the lowered flavorhofhfat score for this
sample. But Lea(l939), Moran(l935), and many other investigators,
are agreed that beef fat is relatively resistant to oxidation except
when frozen and stored for long periods of time(18 months or longer).

Analysis of variance(Table 15) of peroxide values for differences
due to treatment and cold storage, showed that differences due to cold

storage were significant.

Table 15. F values from.analysis of variance of peroxide values

 

 

Source of variation F values
Treatment 2.38
Cold storage 2.8hi

 

* p, less than 6.05, greater than 0.01

Free fatty acids in fat

-‘

Although free fatty acid deve10pment does not necessarily parallel
rancidity develoPment, it is a measure of'hydrolytic decomposition of
the fate. The/fggty acids values for each animal were variable with
treatments fbr the four aging periods. However, there was a progressive
increase in free acidity shown from cold storage through both intervals
of frozen storage. The values for four months' frozen storage were
approximately twice those for cold storage or one week frozen storage.
The extremely high value for zero aging and fourwmonths' frozen storage
might be taken as an index of degree of attack by microorganisms capable
of splitting fats(Lea, 1931). But the palatability scores for this
same period, did not substantiate this probability, since they indicated
a desirable- fat flavor.

-hh-
Analysis of variance(Tab1e 16) between free fatty acid values
showed that differences due to treatment were highly significant and

the differences due to cold storage significant.

Table 16. F values from analysis of variance of free fatty acid values

 

 

Source of variation F values
Treatment 50.22**
Cold storage 2.96%

 

** p, less than.0.0l
*‘p, less than 0.05, greater than 0.01

In the discussion on the scores for flavor of fat(page 31), it
‘was brought out that the score for 167 hours aging plus four months
frozen storage was somewhat low. The increase of free fatty acids
and/or peroxides in fat is usually considered toindicate development
of rancidity with associated off-flavor. In comparing the free fatty
acid and peroxide data with the scores for flavor of fat, it was
apparent that the increased free fatty acid found in Animal I was
associated with a low fat score for this sample. However, the in-
creased peroxide value found in Animal IIat the same treatment
period was not associated.with a low score. This was not unexpected ,
since the peroxide value, although increased, was still below the
10 milliequivalents per kilogram of fat level considered to indicate
obvious off-flavor(Watts, l9h7)o Table 17, page h5,presents the

free fatty acid values for this study.
PE

The pH values for both animals(Talfle 18, page he) showed a
definite increase in acidity with aging in cold storage. The pattern

- hS -

Table 17. Free fatty acid values of unfrozen and frozen raw fat
from longissimus dorsi muscle of beef1

Percent Oleic acid

 

 

 

Aged, hours ‘

Treatment at hooF. Animal I Animal 11
Unfrozen 0 .30 .28
5 .27 .30
2h , .23 .27
167 .31 .LD

Mean.values .28 .31
Frozen ‘- 1 week 0 038 - 03h
5 .31 .31
2h o3h .30
167 036 039

Mean values .35 .3h
Frozen - h months 0 ' 1.17 .h2
S .77 .50
2h .5h .56
167 .88 .51

Mean values .8h .50

 

1
Figures are averages fer two steaks(right and left sides)

from longissimus dorsi muscle from each animal

-146-

Table 18. pH values of unfrozen and frozen raw tissue from
longissimus dorsi muscle of beef

 

 

Aged, hours
Treatment at hboF. Animal I Animal II
Unfrozen O 6068 6. Sb.
5 6.38 6.h1
2b 5.81 6.0h
10? Soéh 5077
Frozen - 1 week 0 5.66 5.72
5 5.66 5.62
2h 5.86 5.52
167 6.06 5.90
Frozen - h months 0 5.68 5.83
5 5.72 5-75
2h 5.69 5.96
167 5.8h 5.81

 

l .
Figures are averages for two steaks(right and left sides)
from longissimus dorsi muscle from each animal

- h7 -
for each animal was similar in trend. The pH reaponse of the animals
during one week frozen storage was variable. At the 167—hour period,
three ofhthe four samples from the two frozen storage periods showed
an increase in alkalinity. Increased alkalinity after frozen storage
of four months has been reported by Beard and Nelson(l9h0) and.McClurg(l9ho).

Histological Changes
Explanation of descriptive terms

The terms used to describe the microscopic observations made in
this study have been used by Harrison(l9h7) and other investigators
in the food research laboratory at Iowa State College.

Rigor node: This term is used to describe a particular kind of

 

contraction of the muscle fiber. Cross-striae are much closer together
than in the normal fiber, and on each side of the contracted area is a
rarefied area in which cross-striae are much wider than usual or
sometimes thrown.out of alignment. In the contracted part of the
node the fiber bulges so that it is wider than the normal fiber.
Paul, et al.(l9hh), stated that a rigor node indicated a state of
active contraction.

Eggs; The term wave is selfbexplanatory. However, waves may
be macroscopic or microscOpic in size, with V or U bends. They may
be deep or shallow, or may be an indentation along the edge like a
sca110p, or there may be many folds or "S" twists; each fiber shows
variations. The waves maybe rhythmic in that a pattern is repeated
over and over along a fiber, or in that all fibers in certain areas
of the sections are involved in the same pattern.

‘chgggz 4A suddenly rounded curve is referred to as a kink,and

nmdtiple kinks as twists. Zig-zag(z-z) contractions describe sharp,

-148-
angular bends in the fibers which give an accordian pleated effect.
The zig-zag contractions, kinks, "S" twists and waves are represent-

ative of passive contraction, according to Paul, et al.(l9hh)o

Disintegration: This is a term applied to loss of the histo-

 

logical characteristics of the protOplasm of the fiber, that is, the
“cross or longitudinal striae. If the sarcolemma remains intact, the
disintegrated material within the fiber appears granular. If the
sarcolemma is entirely broken, the disintegrated material may have
disappeared leaving a blank space in the.fibers. With a slight break
in the sarcolemma, granular material may exude and be noticeable

around the break.

Storage changes

 

The prominence of the longitudinal striae in the longissimus
dorsi muscle fiber was an outstanding characteristic throughout the
histological changes. Contrary to the results reported by Harrison
(l9h7), the cross-striae were evident at various times under low
power. Harrison found.that they were visible only under high power.

Cold storag_: The most noticeable microscOpic changes which

 

occurred in raw samples in cold storage were as follows;

1. The samples with no storage showed poor differentiation
of the fibers and evidence of beginning rigor. The loose z-z
effect of passive rigor was noted.

2. After 5 hours storage, a definite pattern of zig-zag effects
and "S" twists had become pronounced.

3. At 2h.hours cold storage, active rigor nodes were more
numerous; z-z and "S" twists were less noticeable. The number of

fractures across the fibers had increased over the few scattered ones

-19-
noted in some samples after 5 hours in cold storage.

h. The samples held 167 hours in cold storage showed extensive
evidence of thinning of the cell contents, increased fractures across
the fibers and often on each side of rigor nodes, and almost complete
disappearance of z—z contractions. The fibers had become straight
and fragile. Longitudinal and cross-striations had disappeared in
the disintegrated areas. Breaks or fractures across the fibers became

increasingly evident from 5 hours through 167 hours aging.

Typical sections for these storage period changes are shown
in Figures 3 and h, pages 51 and 52. Figure 5a, page 53, shows a
higher magnification of the rigor node of active contraction, and

5 b, a higher magnification of the “S" twist of passive contraction.

The most prominent microscopic manifestation in the cooked
samples was evidence of extreme heat rigor in the 0 and 5—hour
storage samples. This type of rigor does not show up in samples
aged 2h hours at h60F. prior to cooking. The other changes found
in the cooked samples were the same as those in the uncooked samples
(Figures 3, h, and 5). At times, cooking of the steak samples

appeared to intensify the various effects present in the raw samples.

Figure 6, page Sh: shows extreme heat rigor produced during
deep-fat frying of an unaged steak sample. Figure 6b is a higher

magnification of the same effect shown in Figure 6a.

Frozen storag_: The four most noticeable histological changes

 

_ in the raw cold storage samples(Figures 3, h, and 5) were evident in

.frozen'raw.sample. In the frozen samples, the changes frequently

-m-
occurred at an earlier aging period than in the unfrozen samples.

It appeared evident that the process of aging continued in frozen

storage.

Freezing intensified the microscopic changes found in the
raw cold storage samples. It produced an effect similar to cooking
of the cold storage samples. Disintegration and fragility of the
fibers seemed to appear at earlier aging periods.

Histological sections representing 5, 2b, and 167-hours of

aging plus frozen storage of the samples are shown in Figures 7 and
8, pages 55 and 56.

The cooked frozen storage samples displayed evidence of heavy
granulation outside and within the fibers. '

Figure 9a shows noticeable areas of disintegration in the fibers
at 5 hours aging plus feur months frozen storage. Figure 9b, page 57,
is typical of’heavy granulation noted in cooking the frozen samples.

Breaks in fibers

The two types of breaks which appeared in the muscle fibers were
the sharp fractures and disintegration of the muscle fiber, as found
by Paul, et a1.(19hh). The fractures occurred primarily at the z-z
ridges and kinks, and the disintegrated areas were most often evident
on each side of the contracture nodes. Disintegration increased con?
siderably as both cold storage and frozen storage time increased. It
is noteworthy that the highest tenderness scores in the palatability
tests given at the 167-hour aging period for all three storage treat—

ments, were for those steaks in which the greatest number of fractures

-51..

Figure 3. Changes during cold storage of longissimus dorsi fibers.
(longitudinal sections of uncooked samples)

Figure 3a :

no storage; fibers poorly
differentiated; somewhat
wavy; longitudinal striae
prominent (12 5x)

 

Figure 3b:

5 hours cold storage;
definite over-all
pattern of zig-zag(z-z)
effect; example of
passive rigor(125x)

 

 

-52-

Figure 1;. Changes during cold storage of longissimus dorsi fibers.

(longitudinal sections of uncooked samples)

Figure ha:

21; hours cold storage;
fibers show contracture
node(10wer left center);
z-z effect in fiber
immediately above node;
"S“ twists in fibers at
tap and bottom of picture

(1251)

Figure hb:

167 hours cold storage;
fibers show increased
fragility; numerous
fractures; t ' of
cell contents(125:

 

 

 

 

 

-53..

Figure 5. Rigor changes in cold storage of longissimus dorsi fibers.
(longitudinal sections of uncooked samples)

Figure 5a:

5 hours cold storage;
rigor node of active
contraction showing
contracture bulge and
stretched areas on
side of node(550x)

Figure 5b:

2h hours cold storage; ‘
"S" twist of passive ,
contraction(550x) l

 

-514-

Figure 6. Extreme heat rigor produced in cooked, cold storage
sample of longissimus dorsi fibers. (longitudinal
sections of cooked sample)

   

    
     

    

 

 

Figure 6a: 1 ‘-
no storage showing extreme ' :1 T as,“ 31
heat rigor’from cooking | — I (‘3 u; it Law
(1253) | ‘ p q, ,3 I“:

I. .‘.M‘“'}' ‘.¢‘Lv"v\"s \\,Lé

‘ LTL‘IMLJT " m

1 . " .

Figure 6b: .

no storage; higher
magnification of extreme
heat rigor in Fig. 6a.
(5502:)

 

as.

Figure 7. Changes during frozen storage of longissimus dorsi fibers
(longitudinal sections of uncooked samples)

Figure 7a:

5 hours cold storage plus
h.months frozen storage;
fibers wavy, well differ-
entiated ; shows contrac-
ture node and crinkles

of rigor(125x)

 

Figure 7b:

2h hours cold storage plus
h.months frozen storage;
thinning of fiber areas,
longitudinal fracture in
lower left-hand corner;
tight z-z effect in
connective tissue diagonally
through center (125x)

 

 

-56-

Figure 8. Changes during frozen storage of longissimus dorsi fibers.
(longitudinal section of uncooked sample)

167 hours cold storage
plus 1 week frozen
storage; fibers straight,
breaks and disintegrated
areas numberous; granulaa
tion within and between
fibers (125x)

 

 

 

- 57 -

Figure 9. Changes during freezing storage of longissimus dorsi fibers.
(longitudinal sections of cooked samples)

Figure 9a:

5 hours cold storage
plus 1; months frozen
storage; passing z-z
effect; fractures and
disintegrated areas
in fibers (125x)

 

 

Figure 9b: 1 «--¢ .. .

167 hours cold storage " Lfmanaa; 1’18

plus 1 week frozen { v 5’- -- ~--_i__,,ac-.- -,.__,
storage; evidence of “"71. 5%,, “a‘i‘iffifi;,,;j
heavy granulation ‘ ' ,1- "3’ *5? .54.- f."""-‘&‘

outside and within *
fibers. Fat cells 1
over fibers in lower 1
righthand corner(125x)

 

 

-58—

and disintegration within the muscle fibers were found.

Paul stated that the breaks in the fibers might be the result
of either a) autolysis by tissue enzymes, b) physical stress on the
stretched areas between the contracture nodes, or c) connective

tissue contraction.

SUMHARX AND CONCLUSIONS

The effects of cold storage and frozen storage on the palatability
and histological appearance of longissimus dorsi muscle of beef were
investigated. Each of four muscles from two animals was divided into
2h one-inch steaks and arranged in randomized right and left pairs.
Steaks were aged 0, 5, 2h and 167 hours at h60F. At the end of each
aging period b steaks were deep-fat fried at 150°C. to an internal
temperature of 63°C.; 8 steaks were frozen at -26°C., and l) h stored
for one week at 0°F., and 2) h stored for h.months at 0°F. The cooked
steaks were scored subjectively for appearance, aroma, juiciness,
flavor of fat and lean, texture, tenderness and general conclusion.

The pH of the raw, lean tissue and peroxide values and free fatty acids
in the raw fat were determined. Histological sections of raw and cooked
samples were made to determine microscopic changes in fibers in cold

storage and frozen storage.

The palatability scores showed that appearance, aroma and
juiciness were little affected by cold storage or frozen storage;
flavor scores for fat and lean increased with frozen storage; texture,
tenderness and general conclusion scores varied within each treatment
and decreased in score with extended frozen storage. In comparison
with cold storage, this study has shown a definite increase in tender-
ness at the 2hahour level in frozen storage, a slight increase in
tenderness in frozen storage at the 167-hour period, and a decided
decrease in tenderness at the O and 5-hour aging periods. Correlation
between shear value and tenderness score was highly significant, and
between shear value and texture score significant. The correlation
coefficient between cooking time and percent cooking losses was highly

significant. Percent cooking loss per minute cooking time was unaffected

_ 60 -
by cold storage or frozen storage. Peroxide and free fatty acid
values increased slightly in frozen storage. The change in free
fatty acids was most pronounced after four months frozen storage.
The pH values of lean tissue showed increased acidity with cold
storage and a slight decrease in acidity in four months frozen
storage. The histological changes in muscle fibers for both
storage treatments progressed from.poor differentiation in fibers
through rigor stages to fractures and disintegration. Freezing
and cooking both appeared to intensify the changes found in cold
storage. The most prominent manifestation in the cooked samples
was evidence of extreme heat rigor in samples with little or no

cold storage.

0n the basis of these results it appears that:
l. The palatability factors of appearance, aroma, and
juiciness were little affected by either cold storage
or frozen storage; flavor of fat and lean, texture,
tenderness, and general conclusion factors were more
noticeably affected by cold storage.or frozen storage.
2. Tenderness scores in cold storage paralleled the onset,
height and dissolution of rigor; by comparison.with
cold storage, tenderness in frozen storage decreased
sharply in 0 and 5—hour aging periods, increased markedly
at the 2hphour period, and showed slight tenderness
increases at the 167-hour period.
3. There is an acidification of muscle in cold storage
and a slight rise in alkalinity in extended frozen storage.
h. Peroxide development within the intervals studied was

too small to indicate oxidative rancidity.

-61...
5. Free fatty acids showed significant changes in cold storage
and frozen storage that might indicate chemical decomposition.
6. The changes in tenderness were paralleled by histological
appearance of rigor nodes in the least tender samples and by

areas of disintegration in the most tender ones.

LIST OF REFERENCES

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, 19146a. Aging of beef before freezing causes flavor loss,
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, l9146b. Effect of aging and subsequent freezing on beef tenderness.
USDA Bur. Animo Ind. Anne Rept. for 19145-1460

Artyokh, I. 19142. Changes in the protein fractions in frozen meat in
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Bate-finith, E. 0., 19148. Observations on the pH and related prOperties
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Beard, F. J. , and Nelson, P. 1.1., 19140. Influence of low temperatures
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Brady, D. E., 19147. A study of the factors influencing tenderness and
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, 1916. Quality of frozen beef depends on many factors.
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, Frei, P., Hickman, C. W., 19142. Effect of freezing rate on
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Bray, Re We, Vail, Ge Fe, and MaCkintOSh’ De Le, 191.120 Influence Of
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Child, A. M., and Paul, P., 1937. Effect of thawing and cooking frozen
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Cline, J. A., Trowbridge, E. A., Foster, H. T., and Fry, H. E., 1930.
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Craghead, c. w;, 1938. A study of the effect of temperature and time
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Deatherage, F. E. , and Harsham, A. , 1914?. Relation of tenderness of
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Drosdov, S. S. and Drosdov, N. S., 1936. Changes in meat during storage.
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Ewell, A. 111., 19140. The tenderizing of meat. Refrig. Engr. 39: 237-210.

- 63 -

Gortner, W. A., Erdman, F. S., and.Hasterman, N. K., 19h8. Principles
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Halliday, E., and Noble, 1., l9h3. Food Chemistry and Cookery. U. of
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Hammond, J., 19h0. Some factors affecting the quality and composition
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Harrison, D. L., l9h7. Histological, physical and organoleptic changes
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Hankins, 0. G., and Hiner, R. L., 19h0. Freezing makes beef tenderer.
Food Ind. 12:(1), 119-51.

19h1. Quality of meat as affected by freezing temperature.
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, 19hh. Evidence strong that freezing tenderizes meat.
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Helser, M. D., 1923. Farm.Heats. MacMillan Co., pp. 81 — 11h.

 

 

Heiss, R., 1936. The freezing of feadstuffs. Angew. Chem. h9zl7-21,
19360 Chemo Abs. 30, 1875. .

Hickman, R. 0., 19h6. Problems in packaging meat products. Nat. Prov.
1114: (16 )9 76-7613.

Hiner, R. L. and Hankins, O. G., 19h1. Tenderness of beef as affected
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, 19h6. Effect of temperature of
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JOur. Anim. Sci. 5:fi0h.

: l9h7o Temperature of freezing affects
tenderness of‘beef. Food Ind. 19:1078-1081.

 

Hiner, R. L., Madsen, L. L., and Hankins, 0. G., 19h5. Tenderness of
beef 12 relation to temperature of freezing. Food.Res. 10:
312-32 .

Hoaglund, R., McBride, C. N., Powick, W} G., 1917. Changes in fresh
beef during cold storage above freezing. U.S.Dea. Bull. hh3.

Horne, C..A.(,3 1937. The aging and tendering of meat. Ice and Refrig.
92:1 9.

Howe, P. E., 1932. Cooperative meat investigations: Development of
methods for laboratory study of meat, Am. Soc. of Animal Prod.

-61;-

Kiermeier, P., and Heiss, R., 1939. Experiments on the keeping
quality of beef fat tissues and pork fat tissues at low
temperatures. Z. ges. Kalte—Ind. h639l-9S, 111-118, 1939.
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Lea, C. H., 1931. Chemical changes in fat of frozen and chilled.meat.
Part II. Chilled beef. Jour. Soc. Chem.Ind. 50:215T-22OT.

, 1933. Chemical changes in the fat of frozen and chilled
meat. Part IV. The protective influence of CO on the fat of
beef stored at 0° C. Jour. Soc. Chem. Ind. 53:9T-12T.

 

, 1935- Dept. Sci. and Ind. Res.,Food Investigation Special
eport NO- héo Rancidity in Edible Fats.

, 1939- Rancidity in Edible Fats. First Am. Edition, New
York, Chemo PIIblo Co., Inc.

 

Lowe, B., 193h. Mechanical measurement of tenderness of raw and
cooked beef. Unpublished.M.S. Thesis, U. of Chicago.

, 19h3. Experimental Cookery. Second Edition, New York,
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, 19h5. Processing and storage of frozen foods. Jour. Am.

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Maximum, A. A., and Bloom, W., 19h2. A Textbook of Histology. Fourth
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McClurg, B. R., 19h0. Quality and palatability of meat after storage
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Mackintosh, D. L., Hall, J. L., and vail, G. E., 1936. Some
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McLocklan, H., 1937. Standardizing methods of broiling beef steaks and
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Miller, J. 8., Blakeslee, L. H., and Gortner,‘W. A., 19h7. The effect
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Mitchell, H. H., Hamilton, T. S., and Haines, W. T., 1928. Some factors
affecting the connective tissue content of beef mmscle. Jonr.
of Nutr. 1: 165-178. .

Mohler, J. 12., 1939. Reportd’ chief of Bur. of Anim. Ind. USDA 10.

Moran, T., 1929. Recent advances in low temperature preservation of
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, 1935. Post—mortem and refrigeration changes in meat. Jour.
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_ 65 -

Moran, T., and Smith, E.C.B., 1929. Post-mortem changes in animal
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Paul, P., and Bratzler, L., l9h9. (Private communication.)

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, and Koonz, C. H., 19h1. Freezer storage temperature
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(6), 571 - 580.

, Strandine, E. J., and Koonz, C. H., 19h5. Comparative
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09.

Richardson, W. D., and Scherubel, E., 1908. The deterioration and
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1515 - l56h.

Rockwood, B. N., Ramsbottom, J. E., and Mehlenbacher, V. G., 19h7.
Preparation of animal tissue fats for determination of peroxides
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Shrewsbury, C. L. Jordan, R., Andrews,F. N., McCulloch, R. J., and King,
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_ 66 -

Steiner, G., 19hl. The effect of frozen storage on the mechanical
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1914.10 Chem Abs. 37: 3811.3.
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Winkler, C. A., 1939. Tenderness of meat. I. A recording apparatus for
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Jour. Res. 17D: 8 - 1h.

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