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Cholesterol Content of Broiler Breast Fillets Heated With and Without the Skin in Convection and Conventional Ovens1
Cholesterol Content of Broiler Breast Fillets Heated With and Without the Skin in Convection and Conventional Ovens 1 K. J. PRUSA AND M. M. LONERGAN Food and Nutrition Department, Iowa State University, Ames, I A 50011 (Received for publication September 19, 1986)
1987 Poultry Science 66:990-994 INTRODUCTION
Broiler breast fillets have become a popular item for fast food, convenience food, and grocery operations. Boned breast fillets can be purchased fresh or frozen with a wide variety of product types available to the consumer. Various factors, such as presence or absence of the skin and cooking method may affect final product characteristics and composition. Food composition tables (US Department of Agriculture (USDA, 1979) indicate that raw and roasted chicken breast meat with the skin contains more fat and less moisture than breast meat only. Raw breast with skin contains more cholesterol when compared with raw breast alone, but roasted samples contain similar cholesterol amounts. Mickelberry et al. (1964) indicated that heating (parameters not specified) breast meat with or without the skin would give similar cholesterol amounts because of cholesterol loss from the skin. In contrast, studies at the University of Nebraska (USDA, 1979) indicated that cholesterol is concentrated in (not lost from) turkey skin during heating, going from 91 to 113 mg/100 g; this is the same behavior observed in intact muscle (Prusa and Hughes, 1986). Light turkey meat roasted with the skin
'Journal Paper Number J-12426 of the Iowa Agriculture and Home Fxonomics Experimental Station, Ames, IA; Project Number 2113.
contained more fat and cholesterol than turkey roasted without the skin. Mickleberry et al. (1964) cited a low protein content in chicken skin and, thus, less structure to retain fat and cholesterol during cooking. However, turkey skin contains protein amounts similar to those in chicken skin (USDA, 1979) and its cholesterol is concentrated during heating also. Cholesterol associated with membrane structures in skin, according to Feeley et al. (1972), should not be lost during heating. If it would be possible to lower the cholesterol content of chicken skin during heating, this process may be improved by broiling. Broiling has been found to reduce the fat and cholesterol content of high-fat ground beef (Kregel et al., 1986). Convection oven heating is a relatively new method of cooking meat that has received limited attention. Convection heating has several advantages over conventional oven heating of poultry. For turkey, these include more rapid heating (Prusa and Hughes, 1986) and greater oven energy efficiency (McNeil and Penfield, 1983) without reduction in product quality characteristics. Convection ovens are equipped with a broiler unit; however, no research could be found investigating the cholesterol and fat content and product characteristics of chicken cooked by convection broiling. Objectives of this study were: 1) to quantify the fat and cholesterol content of raw and cooked chicken breast with or without the skin and 2)
990
Downloaded from http://ps.oxfordjournals.org/ at Purdue University Libraries ADMN on April 13, 2015
ABSTRACT Six treatment combinations for the heating of broiler breast fillets were investigated: three skin variables (heated and analyzed with skin, heated with and analyzed without skin, and heated and analyzed without skin) and two heating systems (convection broiling and conventional roasting). Matched broiler breast fillets were analyzed raw or breaded and heated to 82 C. Raw and cooked samples of meat, skin, and meat with skin were analyzed for moisture, fat, and cholesterol contents. In the raw state, samples of meat with skin contained greater moisture and fat contents, but similar cholesterol contents, when compared with samples of meat alone. Fillets heated by convection broiling had greater cooking losses but shorter heating times compared with conventionally roasted samples. Fillets with the skin removed before or after heating contained more moisture, less fat, and less cholesterol than samples cooked and analyzed with the skin present. (Key words: cholesterol, skin, broilers, heating methods, breast meat)
CHOLESTEROL CONTENT OF BROILER BREAST FILLETS
to compare effects on cholesterol of conventional heating with convection broiling for heating broiler breast fillets. MATERIALS AND METHODS
Weight) x 100. Cooking Loss (%) was calculated as: 100 - (Cooked Weight/Raw Weight) x 100. Moisture, Fat, and Cholesterol Analysis. Samples of raw and cooked meat with skin, meat only, and skin only were ground (Kitchenaide, model K5-A, .31-cm plate, Hobart Manufacturing, Troy, OH) for compositional analysis. Moisture content was determined on a 5 g sample in a Brabender Semiautomatic Moisture Oven (Model 951, Rochelle Park, NJ). Samples were heated at 130 C for 2 h. Total lipid content was determined in duplicate on lipid extract prepared by the Folch procedure (Folch etal., 1957). Five grams of sample were blended with 85 mL chloroform/methanol (2/1, v/v), made up to volume (100 mL), filtered (Whatman 1, Fisher Scientific, St. Louis, MO), and washed with .2 vol distilled water. After complete separation, a 5-mL aliquot of lipid extract was freed of solvent, and lipid content was determined gravimetrically. Cholesterol content was determined according to the method of Searcy and Bergquist (1960) with modifications by Prusa and Hughes (1986). A standard curve was constructed by carrying specific amounts of purified cholesterol through saponification, extraction with hexane, and color development steps. Statistical Analysis. Least-squares analysis of variance using the general linear model procedure was used with the design in Table 1 (Statistical Analysis System, 1982). When F values were significant, least significant differences at the 5% level were calculated. Where no significant interaction between skin variable and oven type were found, main effect means are reported. Correlation coefficients were determined by using variables for raw and cooked samples.
TABLE 1. Design for analysis of variance df Source of variation
Cooked
Raw
Replication Skin variable Oven type Skin variable X oven type Error
3 2 1 2 15
3 2
Total
23
11
6
Downloaded from http://ps.oxfordjournals.org/ at Purdue University Libraries ADMN on April 13, 2015
Treatments. Six treatment combinations for the heating of broiler breast fillets were investigated: three skin variables (heated and analyzed with skin, heated with and analyzed without skin, and heated and analyzed without skin) and two heating methods (convection broiling and conventional heating). A randomized completeblock design with four replications of each treatment was used. Fillet Preparation. Twenty-four fresh chicken breasts were obtained from a commercial supplier. Whole breasts were randomly assigned to one of four replication groups. Right and left pectoralis major muscles (79.4 to 130.0 g) were removed, both placed in a zip-lock heavy-duty freezer bag (2.7 mils), overwrapped with heavy-duty aluminum foil, and frozen (-18 C) in lots of six. Before each heating period, six breast packages were allowed to thaw 24 hr at 3 C. The left pectoralis major muscle was ground (Kitchenaid Model K5-A, .31 cm plate Hobart Manufacturing, Troy, OH) with or without the skin as the treatment dictated to provide raw samples for compositional analysis. Oven Conventional and Convection Heating. The right pectoralis major muscle was breaded with a commercial coating mix. Heating was carried out in a Despatch Rotary Hearth, (Model 152-P, Minneapolis, MN). For conventional heating, fillets were placed on an aluminum pan (30 cm X 20 cm X 2.5 cm) and heated at 163 C. For convection broiling (Farberware, Model 464, Kidde, Bronx, NY), the temperature dial was set on the broil setting, and oven temperature was stabilized at 216 C ± 4 C. Breaded fillets were placed directly on the oven rack 12 cm from the heat source. Oven temperature and fillet internal end point temperature (82 C) were monitored with thermocouples attached to an Omega Digital Thermometer (Model HH-99K, Stamford, CT). Cooking Time and Rate, Breading Uptake, and Cooking Loss. Cooking time was recorded from the time the fillet was placed in the oven until an 82 C internal end point temperature was reached. Cooking rate was calculated by dividing the cooking time by the breaded raw fillet weight. Breaded uptake (%) was calculated as: (Breaded Weight - Initial Weight/Initial
991
PRUSA AND LONERGAN
992
TABLE 2. Moisutre, fat, and cholesterol contents of raw broiler breast meat, breast meat with skin, and skin only1 Contents
Meat only
Skin only
69.10 B 11.25 B
76.08 A 1.42C
53.95^ 36.18 A
69.45 B
63.16 B
93.90 A
225.31°
263.97 a
205.22 b
Meat and skin
Moisture, % Total fat, % Cholesterol, mg/100 g (wet-weight) Cholesterol, rag/100 g (dry-weight)2
Means in a row with different superscripts are significantly different (P<.001). 'Means of four replications. 2
Dry-weight cholesterol values were averaged from the four replications of moisture and wet-weight cholesterol values.
RESULTS AND DISCUSSION
Moisture, fat, and cholesterol contents of raw broiler breast meat, breast meat with skin, and skin only are presented (Table 2). Samples of skin contained the least moisture and greastest fat and cholesterol contents when compared with breast meat only and breast and skin. Breast meat with the skin contained less moisture, more fat, and the same amount of cholesterol (wetweight) as breast meat only. The most recent reported fat and cholesterol values for broiler skin have ranged from 32.81% (Pikul et al., 1985) to 54.92% (Sahasrabudhe et al, 1985) for fat and 71 mg/100 g (van de Bovenkamp and Katan, 1981) to 118.1 mg/100 g (Pikul et al., 1985) for cholesterol. Breast fillets have different raw compositions with or without the skin present. For example, with the skin present, chicken breast meat (raw) contains an appreciable amount of fat (11.25%). Sahasrabudhe et al. (1985) indicated that it was important to determine if skin was present in calculating total lipids consumed from poultry. On a dry-weight basis, the skin and meat and skin contained less cholesterol when compared with the meat only. This may have been due to the relatively low moisture content found in the skin. Breading uptake and cooking loss, time, and rate are reported in Table 3. Samples that were cooked with or without the skin present did not differ in breading uptake, cooking time, cooking rate, or cooking loss. Because skin is a high-fat tissue, cooking broiler breast with skin may increase cooking losses. Fillets cooked without skin did have lower cooking losses when compared with samples heated with the skin, but
the difference was not significant. Fillets broiled in the convection oven heated faster and had greater cooking losses when compared with fillets heated by the conventional oven (Table 3). Convection-broiled samples were heated at a higher temperature (216 C) than conventionally heated samples (163 C). Hoke (1968) indicated that lower yields (greater cooking loss) were found when chickens were heated at 191 C when compared with 163 C. In contrast, Goertz et al. (1964) found no differences in cooking time or cooking loss in broilers that were gas-broiled at temperatures from 177 C to 204 C. Moisture, fat, and cholesterol contents of broiler breast fillets are presented (Table 3). Fillets cooked and analyzed with the skin contained lower moisture contents and greater fat and cholesterol contents (wet-weight) than fillets analyzed without the skin. Contrary results were found by Mickleberry et al. (1964), who indicated that chicken breast heated (no information on cooking method was given except "oven fried'') with or without the skin would contain similar cholesterol amounts. Our results are congruent with the work on turkeys at the University of Nebraska (USDA, 1979) that indicated breast roasts with skin heated at 163 C to 82 C contain more cholesterol than roasts heated without the skin. Fillets that were heated with the skin but that had the skin removed before analysis contained similar moisture, fat, and cholesterol values when compared with fillets heated without the skin (Table 3). It is obvious that the presence of skin during analysis is the contributing factor to the additional fat and cholesterol contents.
Downloaded from http://ps.oxfordjournals.org/ at Purdue University Libraries ADMN on April 13, 2015
Means in a row with different superscripts are significantly different (P<.05).
Skin variable
11.84 a 16.46 a 14.64 a .16 a 64.83 a 3.10 b 73.60 b 209.48 a
12.60 a 17.62 a 17.60 a .15 a 65.49 a 3.82 b 73.71 b 214.26 a
84.00 a
203.13 a
Cooked and analyzed without skin
11.57a 17.46a 16.51a .15a 58.58 b 11.14a
Cooked with/ analyzed without skin
203.41
77.86
12.94 20.18 13.33 .12 61.64 6.01
Convection
Means of four replications.
Dry-weight cholesterol values averaged from the four replications of moisture and wet-weight cholesterol values.
Significance of differences between oven types within production variables is given in table. NS = not significant.
No significant interactions between skin variable and oven type.
***Oven types are significantly different (P<.001).
**Oven types are significantly different (P<.01).
4
3
2
1
ab ' Means for a skin variable effect in a row with different superscripts are significantly different (P<.001) for mo
Breading uptake, % Cook loss, % Cook time, min Cook rate, min/g Moisture, % Total fat, % Cholesterol, mg/100 g (wet-weight) Cholesterol, mg/100 g (dry-weight)4
Production variable
Cooked and analyzed with skin
TABLE 3. Breading uptake, cooking loss, time, rate, moisture, fat, and cholesterol contents of co
m http://ps.oxfordjournals.org/ at Purdue University Libraries ADMN on April 13, 2015
994
PRUSA AND LONERGAN
TABLE 4. Correlation coefficients for selected factors and the cholesterol content of raw and cooked broiler breast fillets Cholesterol content (wet weight) Variable
Raw (n = 12)
Cooked (n = 24)
Fat content Moisture content Cooking time Cooking loss
.92*** -.88*** ..• ...
.59** -.56** - . 1 0 NS1 .09 NS
NS = Not significant.
*'Significant (P<.01). •••Significant (P<.001).
Cholesterol contents calculated on a dry-weight basis were not different among skin variables. Convection-broiled fillets contained less moisture than conventionally heated samples (Table 3). This result is related to the greater cooking losses observed during convection broiling. Fat and cholesterol contents of fillets were similar between oven types. The amount of fat and cholesterol (wet-weight) was not reduced in the fillet by the broiling process. Correlation coefficients relating selected factors and the cholesterol content of chicken are presented in Table 4. In both the raw and cooked state, cholesterol content was positively related to fat content and negatively related to moisture content, as evidenced by the high and significant correlation coefficients. Cooking time and cooking loss of cooked fillets were not related to cholesterol content. Generally, fillets heated by convection broiling had shorter heating times but greater cooking losses when compared with conventionally roasted samples. Fillets heated and analyzed with the skin contained lower moisture contents
REFERENCES Feeley, R. M., P. E. Criner, and B. K. Watt, 1972. Cholesterol content of foods. J. Am. Diet. Assoc. 61:134149. Folch, J., M. Lees, and G.H.S. Stanley, 1957. A simple method for the isolation and purified of total lipids from animal tissues. J. Biol Chem. 226:497-509. Goertz, G. E., D. Meyer, B. Weathers, and A. S. Hooper, 1964. Effects of cooking temperatures on broiler acceptability. J. Am. Diet. Assoc. 45:526-529. Hoke, I. M. 1968. Roasting chickens. J. Home Econ. 60:661-665. Kregel, K. K., K. J. Prusa, and K. V. Hughes, 1986. Cholesterol content and sensory analysis of ground beef as influenced by fat level, heating, and storage. J. Food Sci. 51:1162-1165, 1190. McNeil, M., and M. P. Penfield, 1983. Turkey quality as affected by ovens of varying energy costs. J. Food Sci. 48:853-855. Mickelberry, W. C , J. C. Rogler, and W. J. Stadelman, 1964. Effect of dietary fats on broiler tissues. J. Am. Diet. Assoc. 45:234-239. Pikul, J., D. E. Leszczynski, andF. A. Kummerow, 1985. Influence of fat content and composition on malonaldehyde concentration in chicken meat and skin. Poultry Sci. 64:311-317. Prusa, K. J., and K. V. Hughes, 1986. Quality characteristics, cholesterol, and sodium content of turkey as affected by conventional, convection, and microwave heating. Poultry Sci. 65:940-948. Rhee, K. S., T. R. Dutson, G. C. Smith, R. L. Hosteller, and R. Reiser, 1982. Cholesterol content of raw and cooked beef longissimus muscles with different degrees of marbling. J. Food Sci. 47:716-719. Sahasrabudhe, M. R., N. F. Delorme, D. F. Wood, and C. J. Randall, 1985. Neutral and polar lipids in chicken parts and their fatty acid composition. Poultry Sci. 64:910-916. Searcy, R. L., and L. M. Bergquist, 1960. A new color reaction for the quantification of serum cholesterol. Clin. Chim. Acta 5:192-199. Statistical Analysis System, 1982. SAS User's Guide: Statistics. SAS Inst. Inc., Raleigh, NC. United States Department of Agriculture, 1979. Composition of Foods. Agriculture Handbook 8-5. US Dep. Agric, Washington, DC. van de Bovenkamp, P. and M. B. Katan, 1981. Cholesterol content of chicken skin. J. Food Sci. 46:291
Downloaded from http://ps.oxfordjournals.org/ at Purdue University Libraries ADMN on April 13, 2015
1
and higher fat and cholesterol contents when compared with samples analyzed without skin.
1987 Poultry Science 66:990-994 INTRODUCTION
Broiler breast fillets have become a popular item for fast food, convenience food, and grocery operations. Boned breast fillets can be purchased fresh or frozen with a wide variety of product types available to the consumer. Various factors, such as presence or absence of the skin and cooking method may affect final product characteristics and composition. Food composition tables (US Department of Agriculture (USDA, 1979) indicate that raw and roasted chicken breast meat with the skin contains more fat and less moisture than breast meat only. Raw breast with skin contains more cholesterol when compared with raw breast alone, but roasted samples contain similar cholesterol amounts. Mickelberry et al. (1964) indicated that heating (parameters not specified) breast meat with or without the skin would give similar cholesterol amounts because of cholesterol loss from the skin. In contrast, studies at the University of Nebraska (USDA, 1979) indicated that cholesterol is concentrated in (not lost from) turkey skin during heating, going from 91 to 113 mg/100 g; this is the same behavior observed in intact muscle (Prusa and Hughes, 1986). Light turkey meat roasted with the skin
'Journal Paper Number J-12426 of the Iowa Agriculture and Home Fxonomics Experimental Station, Ames, IA; Project Number 2113.
contained more fat and cholesterol than turkey roasted without the skin. Mickleberry et al. (1964) cited a low protein content in chicken skin and, thus, less structure to retain fat and cholesterol during cooking. However, turkey skin contains protein amounts similar to those in chicken skin (USDA, 1979) and its cholesterol is concentrated during heating also. Cholesterol associated with membrane structures in skin, according to Feeley et al. (1972), should not be lost during heating. If it would be possible to lower the cholesterol content of chicken skin during heating, this process may be improved by broiling. Broiling has been found to reduce the fat and cholesterol content of high-fat ground beef (Kregel et al., 1986). Convection oven heating is a relatively new method of cooking meat that has received limited attention. Convection heating has several advantages over conventional oven heating of poultry. For turkey, these include more rapid heating (Prusa and Hughes, 1986) and greater oven energy efficiency (McNeil and Penfield, 1983) without reduction in product quality characteristics. Convection ovens are equipped with a broiler unit; however, no research could be found investigating the cholesterol and fat content and product characteristics of chicken cooked by convection broiling. Objectives of this study were: 1) to quantify the fat and cholesterol content of raw and cooked chicken breast with or without the skin and 2)
990
Downloaded from http://ps.oxfordjournals.org/ at Purdue University Libraries ADMN on April 13, 2015
ABSTRACT Six treatment combinations for the heating of broiler breast fillets were investigated: three skin variables (heated and analyzed with skin, heated with and analyzed without skin, and heated and analyzed without skin) and two heating systems (convection broiling and conventional roasting). Matched broiler breast fillets were analyzed raw or breaded and heated to 82 C. Raw and cooked samples of meat, skin, and meat with skin were analyzed for moisture, fat, and cholesterol contents. In the raw state, samples of meat with skin contained greater moisture and fat contents, but similar cholesterol contents, when compared with samples of meat alone. Fillets heated by convection broiling had greater cooking losses but shorter heating times compared with conventionally roasted samples. Fillets with the skin removed before or after heating contained more moisture, less fat, and less cholesterol than samples cooked and analyzed with the skin present. (Key words: cholesterol, skin, broilers, heating methods, breast meat)
CHOLESTEROL CONTENT OF BROILER BREAST FILLETS
to compare effects on cholesterol of conventional heating with convection broiling for heating broiler breast fillets. MATERIALS AND METHODS
Weight) x 100. Cooking Loss (%) was calculated as: 100 - (Cooked Weight/Raw Weight) x 100. Moisture, Fat, and Cholesterol Analysis. Samples of raw and cooked meat with skin, meat only, and skin only were ground (Kitchenaide, model K5-A, .31-cm plate, Hobart Manufacturing, Troy, OH) for compositional analysis. Moisture content was determined on a 5 g sample in a Brabender Semiautomatic Moisture Oven (Model 951, Rochelle Park, NJ). Samples were heated at 130 C for 2 h. Total lipid content was determined in duplicate on lipid extract prepared by the Folch procedure (Folch etal., 1957). Five grams of sample were blended with 85 mL chloroform/methanol (2/1, v/v), made up to volume (100 mL), filtered (Whatman 1, Fisher Scientific, St. Louis, MO), and washed with .2 vol distilled water. After complete separation, a 5-mL aliquot of lipid extract was freed of solvent, and lipid content was determined gravimetrically. Cholesterol content was determined according to the method of Searcy and Bergquist (1960) with modifications by Prusa and Hughes (1986). A standard curve was constructed by carrying specific amounts of purified cholesterol through saponification, extraction with hexane, and color development steps. Statistical Analysis. Least-squares analysis of variance using the general linear model procedure was used with the design in Table 1 (Statistical Analysis System, 1982). When F values were significant, least significant differences at the 5% level were calculated. Where no significant interaction between skin variable and oven type were found, main effect means are reported. Correlation coefficients were determined by using variables for raw and cooked samples.
TABLE 1. Design for analysis of variance df Source of variation
Cooked
Raw
Replication Skin variable Oven type Skin variable X oven type Error
3 2 1 2 15
3 2
Total
23
11
6
Downloaded from http://ps.oxfordjournals.org/ at Purdue University Libraries ADMN on April 13, 2015
Treatments. Six treatment combinations for the heating of broiler breast fillets were investigated: three skin variables (heated and analyzed with skin, heated with and analyzed without skin, and heated and analyzed without skin) and two heating methods (convection broiling and conventional heating). A randomized completeblock design with four replications of each treatment was used. Fillet Preparation. Twenty-four fresh chicken breasts were obtained from a commercial supplier. Whole breasts were randomly assigned to one of four replication groups. Right and left pectoralis major muscles (79.4 to 130.0 g) were removed, both placed in a zip-lock heavy-duty freezer bag (2.7 mils), overwrapped with heavy-duty aluminum foil, and frozen (-18 C) in lots of six. Before each heating period, six breast packages were allowed to thaw 24 hr at 3 C. The left pectoralis major muscle was ground (Kitchenaid Model K5-A, .31 cm plate Hobart Manufacturing, Troy, OH) with or without the skin as the treatment dictated to provide raw samples for compositional analysis. Oven Conventional and Convection Heating. The right pectoralis major muscle was breaded with a commercial coating mix. Heating was carried out in a Despatch Rotary Hearth, (Model 152-P, Minneapolis, MN). For conventional heating, fillets were placed on an aluminum pan (30 cm X 20 cm X 2.5 cm) and heated at 163 C. For convection broiling (Farberware, Model 464, Kidde, Bronx, NY), the temperature dial was set on the broil setting, and oven temperature was stabilized at 216 C ± 4 C. Breaded fillets were placed directly on the oven rack 12 cm from the heat source. Oven temperature and fillet internal end point temperature (82 C) were monitored with thermocouples attached to an Omega Digital Thermometer (Model HH-99K, Stamford, CT). Cooking Time and Rate, Breading Uptake, and Cooking Loss. Cooking time was recorded from the time the fillet was placed in the oven until an 82 C internal end point temperature was reached. Cooking rate was calculated by dividing the cooking time by the breaded raw fillet weight. Breaded uptake (%) was calculated as: (Breaded Weight - Initial Weight/Initial
991
PRUSA AND LONERGAN
992
TABLE 2. Moisutre, fat, and cholesterol contents of raw broiler breast meat, breast meat with skin, and skin only1 Contents
Meat only
Skin only
69.10 B 11.25 B
76.08 A 1.42C
53.95^ 36.18 A
69.45 B
63.16 B
93.90 A
225.31°
263.97 a
205.22 b
Meat and skin
Moisture, % Total fat, % Cholesterol, mg/100 g (wet-weight) Cholesterol, rag/100 g (dry-weight)2
Means in a row with different superscripts are significantly different (P<.001). 'Means of four replications. 2
Dry-weight cholesterol values were averaged from the four replications of moisture and wet-weight cholesterol values.
RESULTS AND DISCUSSION
Moisture, fat, and cholesterol contents of raw broiler breast meat, breast meat with skin, and skin only are presented (Table 2). Samples of skin contained the least moisture and greastest fat and cholesterol contents when compared with breast meat only and breast and skin. Breast meat with the skin contained less moisture, more fat, and the same amount of cholesterol (wetweight) as breast meat only. The most recent reported fat and cholesterol values for broiler skin have ranged from 32.81% (Pikul et al., 1985) to 54.92% (Sahasrabudhe et al, 1985) for fat and 71 mg/100 g (van de Bovenkamp and Katan, 1981) to 118.1 mg/100 g (Pikul et al., 1985) for cholesterol. Breast fillets have different raw compositions with or without the skin present. For example, with the skin present, chicken breast meat (raw) contains an appreciable amount of fat (11.25%). Sahasrabudhe et al. (1985) indicated that it was important to determine if skin was present in calculating total lipids consumed from poultry. On a dry-weight basis, the skin and meat and skin contained less cholesterol when compared with the meat only. This may have been due to the relatively low moisture content found in the skin. Breading uptake and cooking loss, time, and rate are reported in Table 3. Samples that were cooked with or without the skin present did not differ in breading uptake, cooking time, cooking rate, or cooking loss. Because skin is a high-fat tissue, cooking broiler breast with skin may increase cooking losses. Fillets cooked without skin did have lower cooking losses when compared with samples heated with the skin, but
the difference was not significant. Fillets broiled in the convection oven heated faster and had greater cooking losses when compared with fillets heated by the conventional oven (Table 3). Convection-broiled samples were heated at a higher temperature (216 C) than conventionally heated samples (163 C). Hoke (1968) indicated that lower yields (greater cooking loss) were found when chickens were heated at 191 C when compared with 163 C. In contrast, Goertz et al. (1964) found no differences in cooking time or cooking loss in broilers that were gas-broiled at temperatures from 177 C to 204 C. Moisture, fat, and cholesterol contents of broiler breast fillets are presented (Table 3). Fillets cooked and analyzed with the skin contained lower moisture contents and greater fat and cholesterol contents (wet-weight) than fillets analyzed without the skin. Contrary results were found by Mickleberry et al. (1964), who indicated that chicken breast heated (no information on cooking method was given except "oven fried'') with or without the skin would contain similar cholesterol amounts. Our results are congruent with the work on turkeys at the University of Nebraska (USDA, 1979) that indicated breast roasts with skin heated at 163 C to 82 C contain more cholesterol than roasts heated without the skin. Fillets that were heated with the skin but that had the skin removed before analysis contained similar moisture, fat, and cholesterol values when compared with fillets heated without the skin (Table 3). It is obvious that the presence of skin during analysis is the contributing factor to the additional fat and cholesterol contents.
Downloaded from http://ps.oxfordjournals.org/ at Purdue University Libraries ADMN on April 13, 2015
Means in a row with different superscripts are significantly different (P<.05).
Skin variable
11.84 a 16.46 a 14.64 a .16 a 64.83 a 3.10 b 73.60 b 209.48 a
12.60 a 17.62 a 17.60 a .15 a 65.49 a 3.82 b 73.71 b 214.26 a
84.00 a
203.13 a
Cooked and analyzed without skin
11.57a 17.46a 16.51a .15a 58.58 b 11.14a
Cooked with/ analyzed without skin
203.41
77.86
12.94 20.18 13.33 .12 61.64 6.01
Convection
Means of four replications.
Dry-weight cholesterol values averaged from the four replications of moisture and wet-weight cholesterol values.
Significance of differences between oven types within production variables is given in table. NS = not significant.
No significant interactions between skin variable and oven type.
***Oven types are significantly different (P<.001).
**Oven types are significantly different (P<.01).
4
3
2
1
ab ' Means for a skin variable effect in a row with different superscripts are significantly different (P<.001) for mo
Breading uptake, % Cook loss, % Cook time, min Cook rate, min/g Moisture, % Total fat, % Cholesterol, mg/100 g (wet-weight) Cholesterol, mg/100 g (dry-weight)4
Production variable
Cooked and analyzed with skin
TABLE 3. Breading uptake, cooking loss, time, rate, moisture, fat, and cholesterol contents of co
m http://ps.oxfordjournals.org/ at Purdue University Libraries ADMN on April 13, 2015
994
PRUSA AND LONERGAN
TABLE 4. Correlation coefficients for selected factors and the cholesterol content of raw and cooked broiler breast fillets Cholesterol content (wet weight) Variable
Raw (n = 12)
Cooked (n = 24)
Fat content Moisture content Cooking time Cooking loss
.92*** -.88*** ..• ...
.59** -.56** - . 1 0 NS1 .09 NS
NS = Not significant.
*'Significant (P<.01). •••Significant (P<.001).
Cholesterol contents calculated on a dry-weight basis were not different among skin variables. Convection-broiled fillets contained less moisture than conventionally heated samples (Table 3). This result is related to the greater cooking losses observed during convection broiling. Fat and cholesterol contents of fillets were similar between oven types. The amount of fat and cholesterol (wet-weight) was not reduced in the fillet by the broiling process. Correlation coefficients relating selected factors and the cholesterol content of chicken are presented in Table 4. In both the raw and cooked state, cholesterol content was positively related to fat content and negatively related to moisture content, as evidenced by the high and significant correlation coefficients. Cooking time and cooking loss of cooked fillets were not related to cholesterol content. Generally, fillets heated by convection broiling had shorter heating times but greater cooking losses when compared with conventionally roasted samples. Fillets heated and analyzed with the skin contained lower moisture contents
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and higher fat and cholesterol contents when compared with samples analyzed without skin.