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Freezing Methods Influence on Fat and Moisture Composition of Precooked Thighs
Freezing Methods Influence on Fat and Moisture Composition of Precooked Thighs L. D. YINGST 1 AND T. L. GOODWIN Department of Animal Sciences, University of Arkansas, Fayetteville, Arkansas 72701 (Received for publication November 28, 1970)
E
Dichlorodiflouromethane is a very lipotropic reagent. It has been observed that chickens frozen with dichlorodiflouromethane develop white desiccated areas similar to freezer burns. The current investigation was conducted to determine whether dichlorodiflouromethane was altering the fat and moisture content, thus allowing the desiccated areas to develop. 1
Present address: Armour and Company, Oak Brooks, Illinois.
MATERIALS AND METHODS
The experimental units for this experiment were a commercial product obtained from a local poultry firm. Only thighs were utilized. The product was breaded and precooked in a steam cabinet prior to freezing. Freezing was achieved using each of the following methods: liquid dichlorodiflouromethane, liquid dichlorodiflouromethane + 5 percent added chicken fat and blast air movement. The freezers using dichlorodiflouromethane were of commercial production size, and the product entered these freezers at either 41 °C. or 21°C. Twenty-four bags, each containing three thighs, from each of the freezing methods were received for analyses. These experimental units were stored in a home type freezer ( — 20°C.) until samples could be prepared. Samples were analyzed either as the precooked product (initial) or after five minutes of deep fat frying in corn oil at 177°C. (cooked). After cooking the samples were cooled for 3-5 minutes, and the muscle and the skin were removed from one of the three thighs. The breading was peeled from the skin, and the muscle and skin wrapped in foil and held for shear press determination. The meat and skin from the two remaining thighs were separated and samples prepared for fat and moisture determination. The skin-breading portion was cut into approximately 1 cm. square pieces, placed in sample jars and frozen ( — 20°C). These samples are referred to as the skin-breading complex. The muscle tissue was emulsified
957
Downloaded from http://ps.oxfordjournals.org/ at North Dakota State University on June 22, 2015
ACH new method that is introduced to process poultry items creates new problems that must be solved before the technique achieves general acceptance. Most of the poultry that is currently processed is blast frozen, but new methods are being introduced. Marion and Stadelman (1958) studied several methods of freezing poultry meat with temperatures ranging from — 12°C. to — 26°C, and freezing times ranging from one-half to ten hours. The rate of freezing did not have a significant influence on the tenderness of the breast muscle. Miller and May (1965) also reported that rate of freezing did not have any influence on tenderness. Studies concerning freezing methods of turkeys (Barrie et al., 1964; Pickett and Miller, 1967) revealed no difference between blast and liquid freezing methods on the tenderness of turkeys. However, Li et al. (1969) noted lower shear values for thigh muscles frozen by liquid nitrogen process for five minutes to a chamber temperature of — 101°C. as compared with those sharp frozen at - 3 0 ° C .
958
L. D. YINGST AND T. L. GOODWIN
TABLE 1.—Treatment means for percentage fat and moisture of muscle tissue and skin-breading complex
Downloaded from http://ps.oxfordjournals.org/ at North Dakota State University on June 22, 2015
cent and moisture in the skin-breading was reduced thirty-three percent by the reheating process. F a t (Dry wt. basis) Percent Moisture The data when analyzed by analysis of Muscle SkinMuscle SkinTissue Breading Tissue Breading variance indicated that the fat content of Cooking Method the muscle tissue was affected by both Initial 1 23.4a 49.7a 67.2a 60.7a D.F.F.2 21.9b 49.8a 64.3b 27.6b cooking and freezing methods (P < 0.01). Freezing Method The fat content of the skin-breading comD41°3 23.4a 48.3b 65.9a 45.3b D21°'i 23.8a 49.1b 66.1a 44.4b plex was affected by the freezing method D+F21°s 23.4a 53.0a 65.6a 45.6b B21°6 20.2b 48.6b 65.4a 41.4a employed but not by the cooking method. Avg. 22.7 49.8 65.8 44.2 There was a significant cooking X freezing 1 Initial represents product precooked and breaded prior to method interaction (P < 0.01) for fat confreezing. 2 Deep-fat fried in corn oil for 5 minutes. tent of the muscle tissue and the skin3 Dichlorodiflouromethane frozen with a product temperature of 41°C. prior to freezing. breading complex. 4 Dichlorodiflouromethane frozen with a product temperature of 21°C. prior to freezing. Freezing the thighs with dichlorodiflouro5 Dichlorodifiouromethane-r-5% chicken fat with a product temperature of 21°C. prior to freezing. methane did not influence the fat content 6 Blast frozen with a product temperature of 21°C. prior to freezing. of the muscle tissue. However, those thighs Means within the same column and factor followed by different letters differ significantly ( P < 0 . 0 5 ) . that were frozen by the blast method contained approximately three percent less fat using an Omni homogenizer and treated in the muscle tissue as compared to those like the skin-breading complex. Moisture frozen with dichlorodiflouromethane. The determinations were made by drying 2-5 g. addition of five percent fat to the dichlorotriplicate samples at 70° C. in a vacuum diflouromethane resulted in an increase of oven for 22-24 hours. The percent crude approximately four percent of fat in the fat of the moisture free samples was deter- skin-breading complex as compared to the mined by extracting them with ethyl ether other freezing method, but a reduction in in a Goldfish fat extraction apparatus using moisture was obtained in the skin-breading A.O.A.C. procedures. Statistical methods complex of those thighs that were blast froused were factorial analysis of variance and zen. Duncan's new multiple range test as deAfter deep-fat frying for five minutes, scribed by Steel and Torrie (1960). the fat contents of the muscle tissue and the skin-breading complex were essentially RESULTS AND DISCUSSION the same for all frying methods regardless Treatment means for percentage fat and of the initial fat content of the product moisture of the muscle tissue and the skin- (Table 2). The muscle tissue of dichlorodibreading complex are presented in Table 1. flouromethane frozen thighs exhibited a deThese data indicate that deep-fat frying of crease in fat content, whereas, the thighs the product after it has been frozen reduces that were blast frozen absorbed fat during the fat content of the muscle tissue (P < cooking. 0.05), but this treatment has no influence Deep-fat frying resulted in a desiccating on the fat content of the skin-breading effect on both the muscle tissue and the complex. Heating in deep-fat exhibited its skin-breading complex. The freezing greatest influence on the moisture content method also reduced the moisture content of the muscle tissue and the skin-breading of the skin-breading complex after deep-fat complex. The moisture content of the mus- frying. Blast frozen thighs showed a cle was reduced approximately three per- greater loss of moisture in the skin-bread-
959
CHEMICAL COMPOSITION OF PRECOOKED THIGHS TABLE 2.—Chemical composition of thighs after five minutes of deep-fat frying Percent Fat Muscle Tissue
Freon - 4 1 ° C . Freon - 2 1 ° C . Freon + 5 % fat --21°C. Blast •-21°C.
Skin-Breading
Percent Moisture Skin-Breading
Initial
D.F.F.
Initial
D.F.F.
Initial
D.F.F.
24.7 25.7 25.4 18.0
22 .0 21 .8 21 .5 22 . J
46.1 48.3 56.7 47.6
50.6 49.9 49.3 49.6
61.5 60.2 60.9 60.3
29.0 28.7 30.2 22.5
SUMMARY Commercially breaded, precooked, frozen thighs were obtained from a local processor and evaluated for chemical composition and tenderness. The chicken parts were frozen by each of the following methods: liquid dichlorodiflouromethane, liquid dichlorodiflouromethane plus five percent chicken fat and conventional blast freezing. The muscle tissue of the precooked thighs contained more extractable fat prior to deep-fat frying than did comparable parts after being deep-fat fried. The blast frozen muscle tissue was lower in fat content than the muscle tissue frozen by the dichlorodiflouromethane methods. The addition of five percent chicken fat to the
dichlorodiflouromethane gave a skinbreading complex which was considerably higher in fat content. Deep fat frying of the frozen products resulted in desiccation of both muscle tissue and the skin-breading complex. Treatments had no effect on the tenderness of the thighs. REFERENCES Barrie, P. J., G. E. Goertz and J. L. Fry, 1964. Acceptability of blast frozen and liquid frozen turkey hens and toms. Food Technol. 18: 565— 567. Li, K. C , E. K. Heaton and J. E. Marion, 1969. Freezing chicken thighs by liquid nitrogen and sharp freezing process. Food Technol. 23 : 107109. Marion, W. W., and W. J. Stadelman, 19S8. Effects of various freezing methods on quality of poultry meat. Food Technol. 12: 367-369. Miller, W. O., and K. N. May, 1965. Tenderness of chickens as affected by rate of freezing, storage time and temperature, and freeze drying. Food Technol. 19: 147-1SO. Pickett, L. D., and B. F. Miller, 1967. The effect of liquid nitrogen freezing on the taste, tenderness and keeping qualities of dressed turkeys. Poultry Sci. 46: 1148-1153. Steel, R. G. D., and J. H. Torrie, 1960. Principles and procedures of statistics. McGraw-Hill Book Co., Inc.
AUGUST 30-SEPTEMBER 2. WESTERN HEMISPHERE NUTRITION CONGRESS III, HOTEL AMERICANA, BAL HARBOUR, FLORIDA SEPTEMBER 13-16. SHORT COURSE ON FOOD INDUSTRY WASTES AND ECOLOGICAL MANAGEMENT, UNIVERSITY OF FLORIDA, GAINESVILLE, FLORIDA 32601
Downloaded from http://ps.oxfordjournals.org/ at North Dakota State University on June 22, 2015
ing complex than the thighs frozen by the dichlorodiflouromethane methods. Temperature of the product as it entered the freezer had no influence on chemical composition. The analysis of variance for shear values for the breaded thighs indicate that the treatments had no effect on the tenderness of the thighs tested. All shear values represented a very tender product.
E
Dichlorodiflouromethane is a very lipotropic reagent. It has been observed that chickens frozen with dichlorodiflouromethane develop white desiccated areas similar to freezer burns. The current investigation was conducted to determine whether dichlorodiflouromethane was altering the fat and moisture content, thus allowing the desiccated areas to develop. 1
Present address: Armour and Company, Oak Brooks, Illinois.
MATERIALS AND METHODS
The experimental units for this experiment were a commercial product obtained from a local poultry firm. Only thighs were utilized. The product was breaded and precooked in a steam cabinet prior to freezing. Freezing was achieved using each of the following methods: liquid dichlorodiflouromethane, liquid dichlorodiflouromethane + 5 percent added chicken fat and blast air movement. The freezers using dichlorodiflouromethane were of commercial production size, and the product entered these freezers at either 41 °C. or 21°C. Twenty-four bags, each containing three thighs, from each of the freezing methods were received for analyses. These experimental units were stored in a home type freezer ( — 20°C.) until samples could be prepared. Samples were analyzed either as the precooked product (initial) or after five minutes of deep fat frying in corn oil at 177°C. (cooked). After cooking the samples were cooled for 3-5 minutes, and the muscle and the skin were removed from one of the three thighs. The breading was peeled from the skin, and the muscle and skin wrapped in foil and held for shear press determination. The meat and skin from the two remaining thighs were separated and samples prepared for fat and moisture determination. The skin-breading portion was cut into approximately 1 cm. square pieces, placed in sample jars and frozen ( — 20°C). These samples are referred to as the skin-breading complex. The muscle tissue was emulsified
957
Downloaded from http://ps.oxfordjournals.org/ at North Dakota State University on June 22, 2015
ACH new method that is introduced to process poultry items creates new problems that must be solved before the technique achieves general acceptance. Most of the poultry that is currently processed is blast frozen, but new methods are being introduced. Marion and Stadelman (1958) studied several methods of freezing poultry meat with temperatures ranging from — 12°C. to — 26°C, and freezing times ranging from one-half to ten hours. The rate of freezing did not have a significant influence on the tenderness of the breast muscle. Miller and May (1965) also reported that rate of freezing did not have any influence on tenderness. Studies concerning freezing methods of turkeys (Barrie et al., 1964; Pickett and Miller, 1967) revealed no difference between blast and liquid freezing methods on the tenderness of turkeys. However, Li et al. (1969) noted lower shear values for thigh muscles frozen by liquid nitrogen process for five minutes to a chamber temperature of — 101°C. as compared with those sharp frozen at - 3 0 ° C .
958
L. D. YINGST AND T. L. GOODWIN
TABLE 1.—Treatment means for percentage fat and moisture of muscle tissue and skin-breading complex
Downloaded from http://ps.oxfordjournals.org/ at North Dakota State University on June 22, 2015
cent and moisture in the skin-breading was reduced thirty-three percent by the reheating process. F a t (Dry wt. basis) Percent Moisture The data when analyzed by analysis of Muscle SkinMuscle SkinTissue Breading Tissue Breading variance indicated that the fat content of Cooking Method the muscle tissue was affected by both Initial 1 23.4a 49.7a 67.2a 60.7a D.F.F.2 21.9b 49.8a 64.3b 27.6b cooking and freezing methods (P < 0.01). Freezing Method The fat content of the skin-breading comD41°3 23.4a 48.3b 65.9a 45.3b D21°'i 23.8a 49.1b 66.1a 44.4b plex was affected by the freezing method D+F21°s 23.4a 53.0a 65.6a 45.6b B21°6 20.2b 48.6b 65.4a 41.4a employed but not by the cooking method. Avg. 22.7 49.8 65.8 44.2 There was a significant cooking X freezing 1 Initial represents product precooked and breaded prior to method interaction (P < 0.01) for fat confreezing. 2 Deep-fat fried in corn oil for 5 minutes. tent of the muscle tissue and the skin3 Dichlorodiflouromethane frozen with a product temperature of 41°C. prior to freezing. breading complex. 4 Dichlorodiflouromethane frozen with a product temperature of 21°C. prior to freezing. Freezing the thighs with dichlorodiflouro5 Dichlorodifiouromethane-r-5% chicken fat with a product temperature of 21°C. prior to freezing. methane did not influence the fat content 6 Blast frozen with a product temperature of 21°C. prior to freezing. of the muscle tissue. However, those thighs Means within the same column and factor followed by different letters differ significantly ( P < 0 . 0 5 ) . that were frozen by the blast method contained approximately three percent less fat using an Omni homogenizer and treated in the muscle tissue as compared to those like the skin-breading complex. Moisture frozen with dichlorodiflouromethane. The determinations were made by drying 2-5 g. addition of five percent fat to the dichlorotriplicate samples at 70° C. in a vacuum diflouromethane resulted in an increase of oven for 22-24 hours. The percent crude approximately four percent of fat in the fat of the moisture free samples was deter- skin-breading complex as compared to the mined by extracting them with ethyl ether other freezing method, but a reduction in in a Goldfish fat extraction apparatus using moisture was obtained in the skin-breading A.O.A.C. procedures. Statistical methods complex of those thighs that were blast froused were factorial analysis of variance and zen. Duncan's new multiple range test as deAfter deep-fat frying for five minutes, scribed by Steel and Torrie (1960). the fat contents of the muscle tissue and the skin-breading complex were essentially RESULTS AND DISCUSSION the same for all frying methods regardless Treatment means for percentage fat and of the initial fat content of the product moisture of the muscle tissue and the skin- (Table 2). The muscle tissue of dichlorodibreading complex are presented in Table 1. flouromethane frozen thighs exhibited a deThese data indicate that deep-fat frying of crease in fat content, whereas, the thighs the product after it has been frozen reduces that were blast frozen absorbed fat during the fat content of the muscle tissue (P < cooking. 0.05), but this treatment has no influence Deep-fat frying resulted in a desiccating on the fat content of the skin-breading effect on both the muscle tissue and the complex. Heating in deep-fat exhibited its skin-breading complex. The freezing greatest influence on the moisture content method also reduced the moisture content of the muscle tissue and the skin-breading of the skin-breading complex after deep-fat complex. The moisture content of the mus- frying. Blast frozen thighs showed a cle was reduced approximately three per- greater loss of moisture in the skin-bread-
959
CHEMICAL COMPOSITION OF PRECOOKED THIGHS TABLE 2.—Chemical composition of thighs after five minutes of deep-fat frying Percent Fat Muscle Tissue
Freon - 4 1 ° C . Freon - 2 1 ° C . Freon + 5 % fat --21°C. Blast •-21°C.
Skin-Breading
Percent Moisture Skin-Breading
Initial
D.F.F.
Initial
D.F.F.
Initial
D.F.F.
24.7 25.7 25.4 18.0
22 .0 21 .8 21 .5 22 . J
46.1 48.3 56.7 47.6
50.6 49.9 49.3 49.6
61.5 60.2 60.9 60.3
29.0 28.7 30.2 22.5
SUMMARY Commercially breaded, precooked, frozen thighs were obtained from a local processor and evaluated for chemical composition and tenderness. The chicken parts were frozen by each of the following methods: liquid dichlorodiflouromethane, liquid dichlorodiflouromethane plus five percent chicken fat and conventional blast freezing. The muscle tissue of the precooked thighs contained more extractable fat prior to deep-fat frying than did comparable parts after being deep-fat fried. The blast frozen muscle tissue was lower in fat content than the muscle tissue frozen by the dichlorodiflouromethane methods. The addition of five percent chicken fat to the
dichlorodiflouromethane gave a skinbreading complex which was considerably higher in fat content. Deep fat frying of the frozen products resulted in desiccation of both muscle tissue and the skin-breading complex. Treatments had no effect on the tenderness of the thighs. REFERENCES Barrie, P. J., G. E. Goertz and J. L. Fry, 1964. Acceptability of blast frozen and liquid frozen turkey hens and toms. Food Technol. 18: 565— 567. Li, K. C , E. K. Heaton and J. E. Marion, 1969. Freezing chicken thighs by liquid nitrogen and sharp freezing process. Food Technol. 23 : 107109. Marion, W. W., and W. J. Stadelman, 19S8. Effects of various freezing methods on quality of poultry meat. Food Technol. 12: 367-369. Miller, W. O., and K. N. May, 1965. Tenderness of chickens as affected by rate of freezing, storage time and temperature, and freeze drying. Food Technol. 19: 147-1SO. Pickett, L. D., and B. F. Miller, 1967. The effect of liquid nitrogen freezing on the taste, tenderness and keeping qualities of dressed turkeys. Poultry Sci. 46: 1148-1153. Steel, R. G. D., and J. H. Torrie, 1960. Principles and procedures of statistics. McGraw-Hill Book Co., Inc.
AUGUST 30-SEPTEMBER 2. WESTERN HEMISPHERE NUTRITION CONGRESS III, HOTEL AMERICANA, BAL HARBOUR, FLORIDA SEPTEMBER 13-16. SHORT COURSE ON FOOD INDUSTRY WASTES AND ECOLOGICAL MANAGEMENT, UNIVERSITY OF FLORIDA, GAINESVILLE, FLORIDA 32601
Downloaded from http://ps.oxfordjournals.org/ at North Dakota State University on June 22, 2015
ing complex than the thighs frozen by the dichlorodiflouromethane methods. Temperature of the product as it entered the freezer had no influence on chemical composition. The analysis of variance for shear values for the breaded thighs indicate that the treatments had no effect on the tenderness of the thighs tested. All shear values represented a very tender product.