ABSTRACT PRELIMINARY STUDY ON EFFECTS OF FOUR COOKING METHODS ON DIELDRIN RESIDUES IN PORK LOIN SAMPLES By Ruth Ellen Maul The purpose of this study was to compare the effect of braising, roasting, microwave energy and broiling on the Dieldrin residue levels in pork loin chops and roasts. Dieldrin content of lean and fat tissue obtained from swine fed known quantities of Dieldrin was compared with the pesticide residue content of similar samples from an animal fed no Dieldrin. Raw and cooked samples as well as the cooking drip were analyzed for Dieldrin residue concentration using electron capture gas chromatography following a hexane-acetone extraction and Florisil-Celite column clean-up. Parts per million of Dieldrin, based on the fat content of the tissue or dr ip, were calculated. Percentages of fat in uncooked lean and fat tissue averaged 2.28 and 83.96, respectively, while percentages of fat in cooked lean and fat tissue averaged 4.14, 4.67, 4.84 and 4.43 and 90.42, 89.42, 86.99 and 81.24 for samples cooked by braising, roasting, microwave energy and broiling, respectively. These percentages did not differ significantly among cooking methods and/or animals. However, the percentage of fat in the drip was higher (P u: H C) H b: 12 13 13 13 14 14 14 15 15 16 17 17 18 18 19 20 20 21 22 Page Dieldrin Residue Levels . . . . . . . . . . . . . . . . . . . . . 24 Uncooked pork loin samples . . . . . . . . . . . . . . . . . 25 Cooked pork loin samples . . . . . . . . . . . . . . . . . . 26 sample weight 0 O O O O O O O O O O O O O O O O O O I Q 0 O O O O 29 Cooking Losses . . . . . 30 Total cooking losses . . . . . . . . . . . . . . . . . . . . 30 Drip losses 0 O I O O O O O O O O O O O O O O O O O O O O O 33 Volatile losses . . . . . . . . . . . . . . . . . . . . . . 33 Time-Temperature Relationships . . . . . . . . . . . . . . . . 34 Maximum internal temperatures . . . . . . . . . . . . . . . 37 SWY AND CONCLUS IONS O O O O O O O O O O O O O O O O O O O O O O O 4 0 L ITmTl-IRE C ITED O O O O O C O 0 O O O O O O I O O O O O O O O O O O O 44 APPENDIX 0 O O 0 O O O O I O O O C O I O O O O O O O O O O O O O O O O 49 iv Table 10. 11. 12. LIST OF TABLES Animal averages and standard deviations for percentage of fat in uncooked lean and fat tissue from pork loin samples taken from threeanimaIS.......................... Animal and cooking method averages and standard deviations for percentages of fat in lean and fat tissue and drip from pork loin samples taken from three animals and cooked by four methods. Analyses of variance for percentage of fat in pork loin samples taken from three animals and cooked by four methods. . . . . . . Animal and cooking method averages and standard deviations for percentage of fat in lean and fat tissue of end and middle slices from roasted pork loin samples taken from three animals.. Animal averages and standard deviations for ppm of Dieldrin residue in uncooked lean and fat tissue from pork loin samples taken from three animals.. . . . . . . . . . . . . . . . . . . Analyses of variance for ppm of Dieldrin residue in uncooked lean and fat tissue from pork loin samples taken from three animal-8. O C O O O O O O O O O O O O O O 0 I O O O O O O O O 0 .Animal and cooking method averages and standard deviations for ppm of Dieldrin in lean and fat tissue and drip from pork loin samples taken from three animals and cooked by four methods. . Analyses of variance for ppm of Dieldrin residue in pork loin samples taken from three animals and cooked by four me thOds O O O O O O O O O O O O O O O O O O O O O O O O O O O 0 Animal averages and standard deviations for ppm of Dieldrin in lean and fat tissue end and middle slices from roasted pork loin samples taken from three animals. . . . . . . . . . . . . Animal and cooking method averages and standard deviations for raw weights of pork loin samples taken from three animals and cooked by four methods . . . . . . . . . . . . . . . . . . Analyses of variance for raw weights of pork loin chops taken from three animals and cooked by three methods.. . . . . . . . Animal and cooking method averages and standard deviations for total, drip and volatile cooking losses from pork loin samples taken from three animals and cooked by four methods. . . . . . . V Page 20 21 22 23 24 24 27 28 28 29 30 31 Table 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. Analyses of variance for total, drip and volatile losses from pork loin samples taken from three animals and cooked by four me th 0d 8 O O 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 Animal and cooking method averages and standard deviations for maximum internal temperatures of pork loin samples taken from three animals and cooked by three methods. . . . . . . . Percentages of fat and ppm of Dieldrin in uncooked lean and fat tissues from pork loin samples taken from three animals . Percentages of fat and ppm of Dieldrin in lean and fat tissues and drip from pork loin samples taken from three animals and cooked by braising and roasting . . . . . . . . . Percentages of fat and ppm of Dieldrin in lean and fat tissues and drip of pork loin samples taken from three animals and cooked by microwaves and broiling . . . . . . . . Percentages of fat and ppm of Dieldrin in end and middle slices of pork loin roasts taken from three animals . . . . . Raw weights of pork loin samples taken from three animals and cooked by four methods . . . . . . . . . . . . . . . . . Percentages of cooking losses from pork loin samples taken from three animals and cooked by braising and roasting . . . Percentages of cooking losses from pork loin samples taken from three animals and cooked by microwaves and broiling . . Maximum internal temperatures of pork loin samples taken from three animals and cooked by three methods . . . . . . . vi Page 32 39 49 50 51 52 53 54 55. 56 LIST OF FIGURES Figure Page 1. Average time-temperature relationships for three braised pork loin samples taken from each of three animals . . . . . . . . 35 2. Average time-temperature relationships for two roasted pork loin samples taken from each of three animals . . . . . . . . 36 3. Average time-temperature relationships for broiled pork loin samples taken from each of three animals . . . . . . . . . . 38 vii ..z a... P. INTRODUCTION The use of pesticides has benefited mankind by enabling him to produce increased crop yields of high quality and to control diseases caused by insect-borne pathogens. However, the effect of continuous exposure to low- level environmental concentrations of pesticides is not yet understood (Anderson, 1965). Pesticide residues are found in all forms of life (Paul, 1965; Braund 35 31., 1969; Whitacre‘gt‘gl., 1967). Limited research has been done on assessing pesticide residue levels in total diet samples (Mills, 1963; Williams, 1964; Duggan 35'31., 1966; Egan £3 21., 1966). In general, the results indicated the average daily intake of Dieldrin and DDT residues was higher than that of residues from other organochlorine pesticides. However, most of these residue analyses have been conducted on raw foods. Crosby (1965) stressed the importance of determining the effect of cooking and other preparative procedures as methods of destroying or reducing pesticide residues in food. Evidence indicates residues of Dieldrin, a chlorinated hydrocarbon, are concentrated in fats and fatty tissues of animal products. Hence, reduction in the pesticide residue content occurs when fat is removed during cooking or other processing (Duggan 35 31., 1966 and 1967). However, limited and conflicting reports are available on the effectiveness of cooking to reduce pesticide levels. It was the purpose of this study to compare the effect of selected cooking methods on the Dieldrin residue levels in pork loins. Dieldrin 1 2 content of muscle and fat tissue obtained from swine fed known quantities of Dieldrin was compared with the pesticide content of similar samples taken from an animal fed no Dieldrin. Uncooked and cooked samples were analyzed. Boneless chaps and roasts from the loin sections were used for the investigation. Roasts were cooked in a 177°C oven while chaps were cooked by braising, microwave energy and broiling. Dieldrin residues were extracted from raw and cooked samples after fat and lean portions had been physically separated. Cooking drip was also analyzed. Following the hexane-acetone extraction and Florisil-Celite column clean-up, the Dieldrin residue concen- tration was determined by electron capture gas chromatography. All data were statistically analyzed for differences attributable to animal and/or cooking method. The findings were evaluated for possible recommendations for preparation of pork loins to minimize Dieldrin residue levels in the cooked meat. REVIEW OF LITERATURE The use of pesticides during growth of fruits and vegetables results in detectable quantities of the chemicals in food at harvest. The sub- stances may exist as a surface deposit or actually penetrate the cuticle of the plant where the residues may remain unchanged within the plant or they may be broken down by the plant to form compounds equally undesirable. The residues may be taken up by animals from their feed, to appear later in meat, fish, eggs and dairy products. The nature and behavior of Dieldrin will be presented. Literature on decreasing amounts of pesticides in foods as well as studies concerned with cooking methods and cooking losses of pork will be reviewed. Dieldrin Dieldrin is a chlorinated hydrocarbon pesticide containing oxygen. The structural formula of HEOD (1,2,3,4,10,lO-hexachloro-6,7-epoxy-l,4,4a,5,6, 7,8,8a-octahydro-l,4-endo,exo-5,8-dimethanaphthalene) is as follows. Cl Cl Cl Dieldrin functions as a nerve poison. It is considered toxic and can be absorbed directly through the skin in harmful quantities. (Frear, 1955; de Ong £5 91..., 19560) Mobility and stability Harris (1969) reported chlorinated hydrocarbon insectcides, including Dieldrin,.Aldrin, DDT and its derivatives, Endrin and Heptachlor, were immobile in the soil. The results of his study suggest the pesticides are incorporated into the soil by physical means and the movement of water through the soil did not affect the pesticide content. Oloffs _£‘gl. (1969) applied Aldrin to the surfaces of cubed radishes, beets, turnips, rutabagas, carrots and parsnips before incubating the samples at 35°C for 24, 48 or 72 hr. The researchers found the Aldrin was converted to Dieldrin at varying rates for the different vegetables. After destruction of the cell structure by grinding or freezing, applied Aldrin did not change in composition. Also, no Dieldrin was formed from.A1drin applied to the boiled root vegetables. Investigating the stability of Aldrin and Dieldrin, Lichtenstein._§__l. (1968) reported both compounds rapidly disappeared from sterile agar in glass-covered petri dishes. The presence of fungi or microorganisms, in general, retarded the disappearance of the pesticides. In the presence of microorganisms, Aldrin was epoxidized into Dieldrin. Decreasing the Amount of Pesticide Residues Washing, paring and/or cooking the foods offer a potential for removing or reducing the pesticide residue levels. Literature pertinent to fruits and vegetables, meat, poultry and milk as well as other foods will be reviewed. Fruits and vegetables Losses of Malathion residues due to processing gooseberries, plums, tomatoes, apples and string beans were investigated by Koivistoinen gt 1. (1964). Approximate losses were: canning, 50% or more; processes with a 5 cooking period of 15 to 20 min, 30 to 50%; juice making by pressing or steaming, 70 to 90%; drying at 75°C for l to 2 days, 90 to 100%; freezing, 40 to 50%. Losses varied from 0 to 79% when fruits were washed in running water for l min. In a related study, Baldwin _£‘_l. (1968) found washing, paring and coring was more effective than cooking for reduction of DDT and its derivatives in apples. The apples were cooked by baking, boiling, broiling, electronic cooking and pressure cooking. The potentials for removing chlorinated hydrocarbon pesticide residues in several vegetables by commercial processing and home preparative procedures have been investigated in a series of studies. Commercial processing proce- dures were more effective than home preparative methods for removing DDT, Malathion and Carbaryl from green beans (Elkins.g§.gl., 1968) and tomatoes (Farrow 35 21., 1968), Parathion and Carbaryl from broccoli (Farrow 35 21., 1969), DDT from potatoes (Lamb'gg‘gl., 1968a) and DDT, Parathion and Carbaryl from spinach (Lamb 25,51, 1968b). Investigating the potentials for removing Guthion and DDT from green beans, Carlin gg‘gl. (1966) reported commercially acceptable canning procedures were more effective than freezing methods. Also investigating the effectiveness of freezing, Beckman gt 21. (1965) studied Parathion residue levels in spinach during a 6-mo storage period. Greatest decline was noted during the first two months of storage. Pressure cooking green beans for 3 min at 15 psi resulted in a greater decrease in DDT and its derivatives than boiling for 12 min or cooking electronically for 6 min according to Hemphill £5 21. (1967). In their study, only traces of pesticides were found in the cooking liquid. Studying potatoes and cabbage, Askewig£.gl. (1968) reported a cooking process such as boiling will lead to a partial reduction of organophos- phorus pesticide level but will not cause complete removal. According to the report, there is a possibility that oxidation may occur during the cooking process. 6 Investigating the effect of soil systemic insecticides on flavor and residue in coffee, Rodriguez _§.gl. (1968) reported no foreign flavor was present. No detectable residues of Disulfoton or its metabolites were found. Absorption of Aldrin and Heptachlor from contaminated soil into five varieties of carrots was investigated by Lichtenstein _E g}. (1965). Concentrations varying from 22 to 89% of the concentration in the soil were markedly reduced by boiling the carrots in water. Boiling also resulted in rapid loss of a naturally occurring pesticide, 2-pheny1ethyiso- thiocynate, in turnips (Lichtenstein‘g£.gl., 1964). NEEE:.222$EEX.EE§IE$H§ Using cuts from beef animals fed DDT-contaminated rations, Carter ‘gg‘gl. (1948) investigated the effectiveness of cooking methods to reduce the pesticide residue level. After broiling loin cuts, roasdng rib cuts, pressure cooking and braising cuts from the round and frying ground round samples, the investigators concluded DDT in beef was not materially decomposed or lost during cooking. For the analyses in this early study, lean and fat components were combined. Drip from only the fried ground round was analyzed. McCaskey 25 31. (1968) found that cooking chicken tissue for 3 hr at 121°C did not greatly affect the content of Ovex or Kethane (chlorinated hydrocarbons), but Telodrin and Chlorodane residue levels were reduced. In a similar investigation by Liska 25 31. (1967), chickens fed DDT-,Lindane-, Dieldrin-, Endrin- or Heptachlor-contaminated rations were cooked in water at 88-93°C for 3 hr and in an autoclave at 15 psi for 3 hr. At the lower temperature, up to 901 of the insecticide content was removed while at the higher temperature, essentially all of the DDT, Lindane, Dieldrin and Endrin disappeared from the body tissues. Examination of the component parts showed Heptachlor, DDT and Dieldrin were removed from the white meat more 7 completely than from the fat; however, fat tissue lost more Dieldrin than dark meat. In a related study, DDT-and/or Lindane-contaminated rations were fed to chickens in a study conducted by Ritchey gt‘gl. (1967). The investigators reported pesticide residue levels were reduced considerably when the chickens were cooked by baking or frying. According to the report, Lindane appeared to enhance the retention of DDT in the tissues. Milk containing Telodrin and.Methoxychlor residues was processed into evaporated, dried and sterilized products. Between 40-50% of the Telodrin residues were destroyed during evaporation while only 10-20% of the residues were destroyed during dried whole milk processing. ‘Methoxychlor residues were more stable to the processing treatments (Stemp gg'gl., 1966). According to a study by Ruzicka.g£.gl.(l967), dried whole milk contained 15% less Dieldrin than liquid whole milk. Langlois gg'gl. (1965) reported routine dairy processing, such as pasteurization, ice cream manufacture as well as cheese and butter-making removed little Endrin, Dieldrin and Heptachlor residues. Also, routine storage procedures were not effective in reducing pesticide levels. Molecular distillation proved successful in removing residues of Lindane, Heptachlor and its derivatives, Aldrin as well as DDT and its derivatives from milk fat (Bills 25.31., 1967). Li _£.gl. (1969) investi- gated the use of high intensity ultraviolet energy to degrade organochlorine insecticide residues in milk and butter oil. One exposure of ultraviolet energy resulted in 96% degradation of Methoxchlor residues in butter oil while smaller percentages of Dieldrin, Heptachlor epoxide, and DDT and its derivatives were degraded. In a study on edible vegetable oils, Gooding 'gt'gl. (1966) investigated the effectiveness of processing on pesticide removal. According to the report, steam deodorization removed all chlorinated hydrocarbon pesticides. 8 Cooking Methods for Pork According to the National Livestock and Meat Board (1965) pork loins are suitable for roasting. Because pork is considered a tender meat, pork chops may be cooked by broiling although the chops are usually best when braised. Meats cooked by microwave energy required less cooking time but have the disadvantage of no surface browning when cooked solely by micro- wave energy. Because the presence of the organism Trichinella spiralis is not detected by routine meat inspection methods, it is essential that the end cooking temperature be high enough to destroy any of these organisms which may be present in pork. The organism is destroyed at 58.3°C; however, to allow a margin of error, a minimum end cooking temperature of 65°C is preferable (Code of Federal Regulations). Braising In an early study, Cline gt‘gl. (1940) compared pork chops braised with and without added water. The investigators concluded cooking losses and cooking times were similar for the two methods but chops braised without added water received the highest palatability ratings. Bowers‘g§.gl. (1966) browned pork chops, 3/4-in in thickness, in an electric skillet set at 216°C for 2 min per side. After water had been added to designated samples, the pans were covered and the temperature reduced to 116°C. The addition of water had little effect on the eating quality, cooking losses or cooking time; however, added water did decrease the degree of brownness of the cooked chops. End cooking temperatures of 77 and 85°C were compared. Chops braised to 77°C were more acceptable, had lower cooking losses and cooked in less time than chops braised to 85°C. IESI lei: juic was fi iii in 'HCV iUic um 9 Roasting temperature and degree 2f doneness 1. (1938) investigated the effect of oven In an early study, Child 35 temperature on the tenderness of pork. From the results of the study, they concluded a constant oven temperature of 163°C was most satisfactory for roasting pork. Investigating fresh rib and loin cuts of pork roasted at oven temper- atures of 149, 163, 177 and 190°C, Carlin £5 §_1_. (1965) concluded all samples cooked at the four oven temperatures to an internal temperature of 77°C were comparable in flavor and tenderness. The roasts cooked to 77°C were juicier, had lower cooking losses and required less cooking time than roasts cooked to an internal temperature of 85°C. From the results of their study, the investigators concluded optimum quality pork roasts resulted when the meat was cooked at an oven temperature of 163 or 177°C to an internal temperature of 77°C. Studying the effect of end cooking temperature on pork loin roasts, Weir 55,31. (1963) found roasts cooked to 77°C had greater yields and higher juiciness scores than similar cuts cooked to 85°C. Included in the study was the effect of oven temperatures of 149, 163, 177 and 204°C on the quality characteristics of the roasts and from the results of the study, the authors concluded 177°C was the most satisfactory oven temperature. Webb‘gg‘gl. (1961) cooked pork loin roasts to end cooking temperatures of 66, 74 and 85°C and found cooking losses, cooking time and flavor scores increased as the internal temperature increased. However, tenderness and juiciness scores showed an inverse relationship with the internal temperature. Using an oven temperature of 177°C, Pengilly £3 31. (1966) cooked pork loin roasts to internal temperatures of 65, 75 and 85°C. All roasts were judged equally acceptable. However, cooking times and cooking losses 10 increased as the internal temperature increased. From the data, the authors concluded an and cooking temperature of 75°C was most satisfactory for pork loin roasts. Microwave cookery Because microwaves have a greater affinity for the polarized water molecule than for ice molecules, a partially thawed piece of meat will cook unevenly (Dungan, 1969). Therefore, Apgar ggIgl. (1959) recommended the meat be completely thawed before cooking. Apgar 55.21. (1959) cooked pork to an internal temperature of 88°C because at a temperature of 85°C the chops appeared pink in color. Carpenter‘gg'gl. (1968) stated 6-8 min were required to cook pork chaps l 1/4-in in thickness by microwave energy. Broiligg Holmes‘gg‘gl. (1966) placed center cut loin pork chops, 1/2- and 3/4-in in thickness, on open wire racks set 2 in from the bottom of aluminum broiling pans. Positioned 8 in from a preheated broiling unit, the chops were cooked to internal temperatures of 77 and 85°C. The results showed chops cooked to 77°C, 6 min per side, were most satisfactory when juiciness scores, cooking losses and cooking times were compared. Cooking Losses According to Weir gt‘gl. (1962), broiling pork chops to an internal temperature of 85°C required less time than braising similar cuts; however, cooking losses were greatest for broiled chops. Using constant temperatures of 150 and 175°C, Cline-gs l. (1940) also found pork chops cooked by broiling had greater losses than similar cuts cooked by braising. Pork chops cooked by microwave energy had greater cooking losses than broiled chops (Carpenter 33.31., 1968). ‘Moore t 3;, (1966) compared pork loin roasts cooked by microwave energy and in a conventional oven. Their 11 study showed samples cooked by microwave energy had greater cooking losses and a reduced residual moisture content than conventionally cooked samples. Ground pork samples cooked electronically and in an electric frying pan showed increased cooking losses for the former samples (Lim £5 51., 1959). Headley‘ggwgl. (1960) reported lamb roasts cooked in an electronic oven required one-fourth of the cooking time, had greater shrinkage in size and were more done than similar roasts cooked uncovered in a conventional oven at 149°C. According to the report, cooking losses were 43 and 35% for electronically and conventionally cooked roasts, respectively. Diel 5am; EXPERIMENTAL PROCEDURE The purpose of this study was to investigate the effect of cooking on Dieldrin residue levels of pork loin roasts and chops. For this purpose, samples were cooked by braising, roasting, microwave energy and broiling. The Sample Immediately after slaughter, (5/21/69 for Dieldrin-fed hogs and 5/22/69 for the control), boneless loin sections were removed from three crossbred York-Hampshire hogs ranging in.weight from 340 to 390 1b and 10 mo in age. The near-term pregnant hogs had been on a normal diet. One of the three, designated as animal 3, was randomly selected as the control. The two other hogs, designated as animals 1 and 2, had been fed nine, 1.56 g of Dieldrin during a 13-day period (5/8/69 to 5/21/69), for a total of 14.04 g of Dieldrin. After chilling the loin sections for 24 to 48 hr at 5°C, a S-in roast was cut from the anterior end of each loin. Roasts were rolled with the exterior fat covering extending over as much surface area as possible before heavy cord was used to tie roasts at each end and in the middle. The remaining portion of the loin section was sliced on a Hobart slicer, model 410, set at 70. All roasts and chops were individually wrapped in Saran and waxed freezer paper, coded, frozen and stored at -23°C until subsequent preparation and analysis. 12 13 Cooking Procedures Following a predetermined randomized schedule and procedures developed in preliminary investigations, samples were cooked by braising, roasting, microwave energy and broiling. Prior to cooking, roasts and chops were thawed for approximately 36 and 18 hr, respectively, in a 5°C refrigerator. Braisigg To obtain time-temperature relationships throughout the 12-min cooking period, a potentiometer lead was horizontally inserted to the center of each chop. Using a Temco hot plate, model HP-ZSlSB, set at and preheated to 200°C for 15 min and a 6 1/4 in West Bend Country Inn teflon II heavy aluminum frying pan equipped with a specially designed thermocouple holder and preheated for 5 min, chops were browned for 3 min per side. The heat was then reduced to 121°C and the pan was covered for the remainder of the cooking period. Following removal of the pan from the hot plate, time-temperature relationships were continuously recorded until the maximum internal tempera- ture had been reached. The chop was then chilled on a small plate, covered with Saran, in a 5°C refrigerator. Roasting Each roast was positioned fat side up on a wire rack contained in a 13 x 9 x 2 in aluminum pan. Two iron constantan thermocouples were positioned in each roast; the first, at the center of the muscle tissue at the middle of the roast; and the second, in the center of the muscle tissue approximately 1/2 in from the end of the roast. Using a Brown Electronic Potentiometer High Speed Multiple Recorder, time-temperature relationships were continuously recorded during cooking. Roasts were cooked individually in a General Electric 30-in compact oven preheated to and maintained at 177°C * 1° with a Versatronik controller and 14 the grids set on medium. When the internal temperature reached 77°C as recorded by the potentiometer lead in the center of the muscle tissue, roasts were removed from the oven. Following removal from the oven, the roasts were allowed to stand undisturbed until the maximum internal temperature had been recorded. The roast was then transferred to a pyrex pie plate, covered with Saran and refrigerated at 5°C for 16 to 18 hr. Microwave cookery Following browning as outlined for the braising procedure, the chop was placed in a 20-oz Pyrex utility casserole dish. The dish was loosely covered with Saran and a 1-in slit was made in the covering. Using a Litton Microwave Oven, Model 550, the chops were individually cooked for 1 min. The chops were then chilled on a small plate after covering with Saran. Broiling After horizontally inserting a thermocouple, each chop was positioned in the center of a 7 1/2 x 11 in aluminum broiler pan. A Westinghouse, built-in oven, model OGZlH, preheated for 10 min with the grid set on broil was used to individually cook chops for 6 min per side. Chops were placed approximately 6 1/2 in from and directly under the heating unit in the center of the oven. The oven door was about 4 in ajar during broiling. Following removal from the oven, the maximum internal temperature was recorded as outlined above. The chop was then transferred to a small plate, covered with Saran and chilled. Cooking Losses Total, drip and volatile losses were calculated for each roast and chop and converted to percentages based on the raw weight of the sample. Total losses were calculated as the difference in raw and cooked weight. 15 Drip losses were determined as the difference in the weight of the pan (and rack for roasted samples) before and after cooking while volatile losses were calculated as the difference in total cooking losses and drip losses. Losses attributable to browning and microwave cooking were each calculated in addition to total losses for this method of cooking. A 5-kg capacity Toledo Scale, model 4030 was used to obtain weights needed to calculate cooking losses. Analyses for Pesticides and Fat Lean and fat tissues were physically separated for all raw and cooked samples before each was separately analyzed for Dieldrin content. Drip from all cooked samples was also analyzed. Prgparation for analyses To prevent possible contamination, all glassware and equipment used for the analysis were thoroughly washed and rinsed before rinsing with acetone. Pans and dishes used for cooking were cleaned in the same manner. A mixture of hexanes was used in all extraction and clean-up procedures and to rinse out all containers to insure inclusion of all samples for the next step. All cooked samples were chilled as outlined above to facilitate physical separation of lean and fat tissues. Using a Mettler balance, model H15, 15 to 20g samples of lean were weighed to the nearest 0.000 g while 2 to 4 3 samples of fat were weighed to the nearest 0.0000 3. For chops, all drip from each sample was analyzed. Pans in which chops were cooked were rinsed with a hexane-acetone mixture to insure inclusion of all drip. For analyses of drip from microwave-cooked samples, losses attributable to browning and microwave cookery were combined. For roasts, all drip was scraped from the rack and pan, poured into a half-pint jar and refrigerated. After the fat portion had congealed, the entire mass 16 was homogenized by blending in a Sorvall Omni mixer, model 17150. The homogenized sample was chilled before a 2 to 3 g sample was weighed to the nearest 0.0000 g for analysis. Extraction Using a ZOO-ml extraction chamber to a Sorvall Omni mixer, samples were blended with 50 m1 of hexane-acetone (2:1) at speed 2 1/2 for 4 min. The speed of the motor had been adjusted so the blade barely moved at the lowest speed. The extract was then poured through a glass wool-lined filtering funnel into a 500-ml separatory funnel, retaining the finely minced sample in the extraction chamber. The blending and filtering process was repeated twice, transferring the sample to drain at the end of the third extraction. The glass wool containing the sample was squeezed to remove all liquid possible. Drip samples were blended just once for extraction using the same speed for 12 min. To remove the acetone, 100 m1 of a 10% sodium chloride solution were carefully added to the separatory funnel and the mixture was gently mixed. The sodium chloride-water—acetone mixture was drained from the funnel. This step was repeated a minimum of three times or until any emulsions which formed during mixing had been eliminated. The hexane-fat-pesticide mixture was transferred to a 30-ml Erlenmeyer flask and dried for 30 min with an excess of anhydrous granular sodium sulfate. After measuring the extract to the nearest milliliter, a 10-ml aliquot was removed for fat analysis. The extract was poured into a 250-ml separatory funnel and 50 ml of hexane-saturated-acetonitrile were added. After shaking vigorously for 4 min, the acetonitrile-pesticide layer was drained into a 500-ml separatory funnel. The acetonitrile partition was repeated twice. Fifty milliliters of hexane were added to the acetoni- trile-pesticide mixture and then the acetonitrile was removed by washing 17 the mixture with 100 m1 of a 10% salt solution. This step was repeated at least three times. The hexane-pesticide mixture was drained into a 300~m1 flask and dried for 30 min with an excess of anhydrous sodium sulfate. The extract was then concentrated to about 10 ml in a 500-ml Kuderna-Danish concentrator over a steam bath. Clean-up ,A 500 x 20 mm Chromaflex chromatographic clean-up column fitted with a coarse porosity fritted disc was prepared by filling for approximately 1/2 in with anhydrous granular sodium sulfate followed by approximately 10 g of a Florisil-Celite mixture (5:1) and then another layer of sodium sulfate. The Florisil, which was received activated at 649°C from Floridin, Inc., was deactivated with approximately 5% water. With stapcocks Open, columns were prewetted with hexane. With hexane 1/4 to 1/8 in above the tap of the sodium sulfate layer, the concentrated extract was added. Approximately 300 m1 of hexane was used to wash the extract through the column. The extract was concentrated as previously outlined to approximately 10 ml. After measuring to the nearest ml, the extract was transferred to a 15-ml culture tube fitted with a teflon-lined screw cap, labeled and stored at -20°C. The extraction and clean-up procedures generally follow those recommended by Shell (1965) except for modifications as outlined above. Fat analysis The 10-ml aliquot was transferred to a dried and tared 50-ml Erlenmeyer flask before it was dried in a Hotpack vacuum oven, model 633, for 3 hr at 70°C. After cooling for 30 min in a dessicator, the sample was weighed. The percentage of fat was calculated using the following formula. Ml extract obtained x dried sample wt T0 m1 aliquot size 1 fat- Sample size (3) 18 Dieldrin analysis All samples were allowed to warm to room temperature. Using a Varian Aerograph gas chromatograph, model 1200-1, equipped with an electron-capture Idetector containing a ZSOmmc tritium foil source, the samples were-analyzed for Dieldrin. The 5' x 1/2" stainless steel column contained 31 SE-30 on 100/120 Varaport #30. A gas flow rate of 25 m1/min at exit port was established and used throughout with the carrier gas of prepurified nitrogen. The injection port temperature was 240°C; column oven temperature was 200°C; and the detector temperature was 215°C. The recorder range was 1 mv and the chart speed was 0.5 in/min. Using the technique of placing the sample between two air blocks of one microliter each, two-microliter samples were injected. Standards were prepared from 99%! pure recrystallized Dieldrin and glass distilled hexane. Standards were run through several times each day of the analyses, and concentration curves were drawn to determine the Dieldrin concentrations of the samples. Dieldrin was qualitatively identified by direct comparison of retention times of the unknown insecticide with those of the standard Dieldrin solutions. Quantitations were based on peak height. The parts per million (ppm) of Dieldrin based on percentage of fat were calculated using the following formula. Ml: extract obtained X Graph reading (ppm) X Concentrated sample size (ml) Correction term1 Sample weight (g) X 1 fat Analyses of the Data The data were analyzed for variances due to cooking method, animal and/or replication. Duncan's multiple range test (Duncan, 1957) was used to pinpoint sources of significant differences. Uncooked and cooked means of appropriate data were compared as outlined by Funk ggwgl., (1968). 1ml extract obtained - 10 m1 removed for fat analysis (a volume correction). l9 _ime-temperature relationships For roasts, time-temperature relationships recorded from each of the two samples from each animal were averaged at lO-min intervals throughout the cooking period. The data were plotted and compared for differences among animals. For chops cooked by braising, time-temperature relationships recorded from the three samples from each animal were averaged at 1-min intervals throughout the cooking period. The data were plotted and examined for differences among animals. Data from broiled chaps were similarly examined and compared with data from braised chops. 1'6 fa 5% Ta] ll RESULTS AND DISCUSSION The purpose of this study was to investigate the effects of braising, roasting, microwave cookery and broiling on Dieldrin residue levels in pork loins. Samples taken from two animals given oral doses of Dieldrin and from one animal fed no Dieldrin were analyzed for Pesticide residue before and after cooking. Time-temperature relationships were continuously recorded during braising, roasting and broiling while total, volatile and drip losses were determined for all cooking methods. Data were analyzed for variance attributable to cooking method and/or animal. Percentage of Fat Percentages of fat were calculated for uncooked and cooked lean and fat tissues as well as for drip losses occurring during cooking. For uncooked samples, the data are presented in Table 1; data for cooked samples appear in Table 2, while percentages of fat for each replication from each animal are found in the Appendix, Table 15 for uncooked samples and Tables 16 and 17 for cooked samples. Table 1. Animal averages1 and standard deviations for percentage of fat in uncooked lean and fat tissue from pork loin samples taken from three animals. Percentage of Fat Animal Lean Fat 1 2.97 t 2.24 85.72 t 5.90 2 1.96 t 0.50 83.41 t 1.21 3(Control) 1.90 t 0.24 82.74 t 3.95 1Each value represents an average of three determinations. 20 21 Table 2. Animal and cooking method averages and standard deviations for percentages of fat in lean and fat tissue and drip from pork loin samples taken from three animals and cooked by four methods. Cooking Percentaggs of Fat Method Animal Lean Fat Drip Braisel 1 4.34 f 1.01 88.67 1: 4.86 56.87 t 25.40 2 4.28 t 2.30 .92.14 ‘t 0.96 39.85 1' 16.92 3(Control) 3.70 f 0.51 90.46 '1' 3.60 33.77 t 8.64 Method Average 4.14 ‘1' 1.20 90.42 '1' 3.44 43.50 1' 18.93 Roast2 1 3.95 f 0.14 89.87 t 7.42 62.66 1' 9.43 2 4.14 t 0.79 90.90 1' 6.17 80.57 * 13.96 3(Control) 5.93 f 1.21 87.49 1: 4.76 80.36 1' 3.14 Method Average 4.67 i 1.19 89.42 t 5.06 74.53 * 11.96 Microwavesl 1 6.78 f 3.73 90.71 i 5.21 60.62 1! 19.11 2 4.29 t 0.73 83.62 “t 5.71 49.11 * 33.62 3(Control) 3.44 't 0.47 86.631“ 3.00 17.03 ‘1: 8.31 Method Average 4.84 ‘1: 2.47 86.99 t 5.10 42.25 * 27.82 Broill 1 6.17 f 1.17 83.16 ‘1‘ 5.27 88.59 * 7.98 2 3.50 f 0 22 75.10 1:10.06 90.65 t 1.83 3(Control) 3.61 f 0 17 85.45 * 5.44 77.92 1' 12.08 Method Average 4.43 t 1 42 81.24 1' 7.82 85.72 t 9.40 1Based on an average of three determinations. 2Based on an average of four determinations. Uncooked_pork loin samples Fat content of the lean tissue averaged 2.28% indicating very little intramuscular fat. In contrast, Batcher 35 El- (1960) reported intramuscular fat values of 6.41 for uncooked pork loins. However, Hammond (1940) reported the amount of fat in a particular muscle varied with age and the location from which the sample was taken. The high standard deviations of the percentages of fat in uncooked lean and fat tissue support this conclusion. Fat tissue samples contained an average of 83.96% fat. Percentages of fat in raw tissue samples did not differ significantly among animals. Also, fat tissue samples from the three animals did not differ significantly in percentage of fat. Animals from.which the samples were taken were the same age, breed, sex and approximate weight. With the 22 exception of the orally administered Dieldrin, all animals had been given the same normal diet. gggkgd_pgrk loin samples Lean tissue cooked by braising, roasting, microwaves and broiling averaged 4.14, 4.67, 4.84 and 4.43, respectively, in percentage of fat. Averages for fat tissue were 90.42, 89.42, 86.99 and 81.24% for samples cooked by braising, roasting, microwaves and broiling, respectively. Neither of these sets of values differed significantly (Table 3). However, standard deviations calculated for replicate analyses from each animal indicate differences among the samples. Several researchers have reported the anterior, center and posterior sections of the longissimus dorsi muscle of pork vary in fat content (Mackey §_t_ 9_l_. , 1954; Batcher £5 91., 1960; Weir g; _a_l_., 1962). Table 3. Analyses of variance for percentage of fat in pork loin samples taken from three animals and cooked by four methods. Source Degrees Meanggguare of of Percentage of Fat Variance Freedom Lean Fat Drip Total 11 Method 3 0.349 45.617 1451.204* Animal 2 2.097 5.785 259.881 Error 6 1.636 11.555 182.109 *Significant at the 5% level of probability Average fat content of the cooked meat appears higher than values given for the raw meat. However, fat content is inversely related to moisture content GMurphy‘ggigl., 1961); hence, as evaporation occurs during cooking, the fat content appears to increase. According to Lowe (1955) the fat content of a muscle is the same before and after cooking when the calculations are based on dry weights. Because the fat molecule is large, it is unlikely that much infiltration of fat would occur during nth CDC 111 11? p: 23 cooking, particularly when the meat is shrinking and water with salts and other soluble components are being squeezed from the interior. Percentages of fat in drip of 43.50, 74.53, 42.25 and 85.72 for samples cooked by braising, roasting, microwaves and broiling, respectively, differed significantly (Table 3). Further analysis (Duncan, 1957) showed values for samples cooked by roasting and broiling were higher (P<0.05) than samples cooked by braising and microwaves and drip from broiled samples contained more fat (Puaou0Hz. “HHS an... 53 3.5 ugh 53 .833 H355 uofiaz .Nammv oavqumm aauuauwn yum mo mumwuaooumm uwaamm wawxooo .waaaaoun van uu>maouuda ma voxooo wad mamawau manna scum cuxwu mwamaum aHoH xuom mo muuu cam «mammau uum van Gama nu Hawuvamwn mo sun can uwm mo mommuamouom .na magma 52 Table 18. Percentages of fat and ppm of Dieldrin1 in end and middle slices of pork loin roasts taken from three animals. Side of Percentages of Fat Dieldrin Residue (ppm) Animal Animal Slice Lean Fat Lean Fat 1 Left 32 5. 04 93. 7 1 o. 018 o. 009 M3 3. 04 75. 34 o. 078 o. 114 Right E 3.71 96.41 0.036 0.017 M. 4.00 93.98 0.055 0.023 2 Left E 3.59 99.92 0.052 0.011 M. 3.56 90.79 0.052 0.007 Right E 5.16 90.15 0.000 0.013 M. 4.24 82.71 0.064 0.015 3(Control) Left E 9.67 92.32 0.008 0.020 M. 3.94 89.40 0.000 0.022 Right E 6.52 83.22 0.000 0.011 M. 3.55 85.02 0.000 0.018 1Calculated on the basis of fat content. 2Slice taken from end of roast. 3Slice taken from.middle of roast. 53 Table 19. Raw weights of pork loin samples taken from three animals and cooked by four methods. Cooking Repli- Raw Weight Cooking Repli- Raw Weight Method Animal cation (g) Method Animal cation (g) Braise 1 l 104 Broil 1 1 104 2 99 2 61 3 75 3 62 2 1 88 2 l 107 2 67 2 107 3 90 3 85 3(Control) 1 148 3(Control)1 134 2 156 2 154 3 149 3 146 Roast 1 1 570 Microwave 1 1 87 2 642 2 92 3 63 2 1 621 2 1 102 2 532 2 8S 3 88 3(Control) 1 1030 3(Control)1 148 2 817 2 150 3 158 54 Table 20. Percentages of cooking losses from pork loin samples taken from three animals and cooked by braising and roasting. Cooking Percentages of Cooking Losses Method Animal Replication Total Drip Volatile Braise l 1 29.9 5.8 21.2 2 27.3 6.1 21.2 3 25 3 2.6 22 7 2 1 25.0 3.4 21.6 2 22.4 3.0 19.4 3 25.6 6.7 18.9 3(Control) 1 24.3 6.1 18.2 2 23.7‘ 3.2 20.5 3 23.5 6.0 17.5 Roast 1 1 32.8 13.2 19.6 2 28.5 8.9 19.6 2 1 29.1 10.5 18.7 2 36.5 16. 20 3(Control) 1 38.3 16.6 21.7 2 35.4 11.3 24 1 55 Table 21. Percentages of cooking losses from pork loin.samp1es taken from three animals and cooked by microwaves and broiling. Cooking Percentage of Cooking Losses Method Animal Replication Total Drip Volatile Microwaves 1 1 36.8 5.7 31.0 2 29.3 8.7 20.6 3 44.4 9.5 34.9 2 1 27.4 5.9 21.6 2 34.1 5.9 28.2 3 33.0 4.4 29.6 3(Control) 1 27.7 10.1 17.6 2 26.0 10.0 16.0 3 26.3 10.3 16.0 Broil 1 1 45.2 12.5 32.7 2 50.8 16.4 34.4 3 54.8 17.7 37.1 2 1 44.9 16.8 28.0 2 44.9 16.8 28.0 3 38.8 12.9 25.9 3(Control) 1 44.0 17.9 26.1 2 39.0 14.3 24.7 3 30.8 8.9 21.9 56 Table 22. ‘Maximnm internal temperatures of pork loin samples taken from three animals and cooked by three methods. _— l _ m Cooking Maximum Internal Temperature Method Animal Replication °C Braise 1 1 88.0 2 88.0 3 94.0 2 1 91.0 2 88.0 3 91.5 3(Control) 1 91.0 2 80.0 3 81.0 Roast 1 1 83.0 79.0 2 1 83.0 2 82.0 3(Control) 1 85.0 2 82.0 Broil 1 1 90.0 2 103.0 3 -..-.. 2 1 90.0 2 91.0 3 90.5 ' 3(Control) 1 94.0 2 81.0 3 81.0 1Data not available. MICHIGAN STATE UNIVERSITY LIBRARIES llllllllll l '11 3145 2513 m 1 III 3 1293