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Accumulation of Free Fatty Acids in Shortening During Chicken Frying Operation1
Accumulation of Free Fatty Acids in Shortening During Chicken Frying Operation 1 T. c. CHEN Poultry Science Department, Mississippi State University, P.O. Box 5188, Mississippi State, Mississippi 39 762 (Received for publication March 31, 1983)
1984 Poultry Science 63:1467-1469 INTRODUCTION
Deep-fat fried chicken parts are sought and accepted by consumers of all ages. Many factors affect the quality of fried chicken products, and the frying medium is a major one. During the deep-fat frying process, the shortening is repeatedly used at elevated temperatures in the presence of air, water, breading compounds, and chicken parts. Under such conditions, the quality of frying medium deteriorates due to hydrolysis, oxidation, and polymerization reactions. Free fatty acids (FFA) are formed during frying as a result of cleavage and oxidation of double bonds (Perkins, 1967) and as a result of "hydrolysis" during the presence of moisture (Weiss, 1970). According to Weiss (1970), the FFA content of a fat is a good indicator of overall quality. The FFA in vegetable oils are the result of the hydrolysis of fats, and the hydrolysis is greatly accelerated by lipase. Kawada et al. (1967) suggested that acidic volatile products may be produced from triglycerides of corn oil during deep fat frying through hydrolysis of the ester linkages, oxidation of longer chain fatty acids, thermal degradation of esters, thermal oxidation of an a-carbon atom of the acid in triglycerides, and an autoxidation of aldehydes and ketones. Kawada et al. (1967) also reported that during the early stage of frying acidic
'Journal Paper No. 5804 of the Mississippi Agricultural and Forestry Experiment Station.
decomposition products are predominantly produced by hydrolysis of triglycerides. The purpose of this study was to investigate the accumulation of FFA in shortening during the chicken frying operation. MATERIALS AND METHODS The cooperation of two commercial fried chicken outlets was obtained. At the beginning of this investigation, the same brand of fresh shortening (pure vegetable frying shortening, NIFDA, GA) was used in their fryers (JCP Frialator, J. C. Pitman & Sons, Inc., NH). The coating ingredients and methods of the fried chicken preparation were also the same. Eightpiece cut broiler parts from 908- to 1135-g carcasses were flour predusted, dipped in a batter, and floured again before being fried at 168 C for 12 min (Yang and Chen, 1980). The amount of raw chicken parts fried, as well as the quantity of shortening added to replenish the fryer, were recorded daily for 12 days. At the end of each day's frying operation, the shortening was filtered and approximately 250 ml of shortening was sampled from each fryer in covered glass jars and held at 2 to 4 C. The collected samples were transported to the laboratory at the end of the sample collection period for analyses. During the investigation period, except for the chicken parts, no other food item was fried in the shortening. Before analyses, the shortening samples were melted at 50 C and mixed individually. The FFA content of the samples was measured according to the procedures described in
1467
Downloaded from http://ps.oxfordjournals.org/ at University of Saskatchewan Library on June 18, 2015
ABSTRACT The cooperation of two commercial fried chicken outlets was obtained. After 12 days of operation, 1246 and 1062 kg of raw chicken parts had been fried at Outlets A and B, respectively. The free fatty acid-(FFA) values of the shortening samples increased continuously throughout the observation period, and the increase was .11 and .25%/100 kg of raw chicken parts fried for Outlets A and B, respectively. In general, the increase of each individual fatty acid appeared to be linear to the quantity of chicken parts fried except for the palmitoleic acid. More than half of the FFA found in the shortening samples were oleic acid. (Key words: chicken frying, free fatty acids)
1468
CHEN
detector. A 183.9 X .64 cm copper column packed with 15% diethylene glycol succinate and 3% phosphoric acid as liquid phase and Chromosorb "W" as solid support was used. The fatty acids were identified by comparing the retention values of unknown peaks with fatty acid standards. UJ e~
RESULTS AND DISCUSSION
< >
4 8 12 PARTS FRIED (X\00kg) FIG. 1. Free fatty acid value of shortening as affected by chicken frying, o, Outlet A; •, Outlet B.
Official Methods of Analysis (American Oil Chemists' Society, 1973) The FFA profiles of the 4, 8, and 12 day's shortening samples were analyzed according to the methods described by Hornstein et al. (1960). Fatty acid composition of broiler breast meat lipid from the ether extraction of oven dried breast meat, along with the fresh shortening samples, was also determined as described by Marion and Woodroff (1963). The fatty acid methylates were analyzed with a Beckman GC-45 gas chromatograph equipped with flame ionization
TABLE 1. Accumulation of free fatty acids (FFA) in shortening during chicken frying1 Shortening sample source: Sampling day: Chicken parts fried, kg: FFA, V As % oleic acid:
A 4 323
8 809
B 12
1.21
1.72
1246 2.24
2.11 27.00 9.06 24.00 109.00 20.00
3.11 62.09 9.63 46.91 234.55 51.88
4.36 91.64 23.38 63.07 279.27 78.54
4 475
8 733
12
1.20
1.75
1062 2.70
2.62 50.70 13.11 37.05 174.65 40.95
3.09 62.03 15.15 44.34 216.67 46.46
3.90 89.90 25.65 47.03 265.56 61.76
Fatty acid/17:0 14 16 16 18 18 18 1
0 0 1 0 1 2
Mean of three determinations.
Downloaded from http://ps.oxfordjournals.org/ at University of Saskatchewan Library on June 18, 2015
If I
After 12 days of operation, 1246 and 1062 kg of raw chicken parts were fried at fried chicken Outlets A and B, respectively. The average amount of fresh shortening replenished during the frying operation was 7 kg/100 kg of raw parts. Free fatty acid values of the shortening samples from both outlets increased continuously throughout the observation period (Fig. 1). The increase in FFA values were .11 and .25%/100 kg of raw chicken parts fried for Outlets A and B, respectively. These values were obtained from the slope of the lines in Figure 1. Results indicated that the FFA content of shortening could be an indicator for determining the extent of the shortening usage in frying chicken operation. The FFA content correlated with the smoking point of the frying medium, (Swern, 1976); an oil with a fatty acid content of .7% had a smoke point of 168 C or higher and one with a free fatty acid content of .4% had a smoke point of 176 C or higher. It is of interest to note that although the FFA content of the used chicken frying shortening was high, no problem related to smoke point was observed when the shortening was heated at 168 C.
RESEARCH NOTE
1469
TABLE 2. Percent fatty acid content of chicken frying shortening and chicken breast meat lipid Sh ortening A
Sample source: Chicken parts fried, kg: Fatty acids 14:0
323
809
Shortening B 1246
475
733
1062
1.4
1.7
1.2
1.2
1.4
15.0
17.8
18.6
16.0
16.5
18.0
3.6
6.1
6.3
5.4
5.4
18 0 18 1 18 2
11.8 56.4 12.1
11.3 51.2 12.2
11.1 50.7 11.6
12.3 55.5 9.7
11.4 54.2 11.3
By calculating against the internal standard, relative concentrations of each individual FFA were summarized in Table 1. In general, the increase of each individual fatty acid appeared to be linear to the quantity of raw chicken parts fried except for the palmitoleic (16:1) acid and the oleic (18:1) acid from Source A samples. More than half of the FFA found in the used frying shortening samples were 18:1 fatty acid. The fatty acid composition of the used shortening samples represents a mixture of fresh shortening and the chicken fat (Table 2). It is of interest to note that the composition of the FFA in used shortening was closer to the fatty acid composition of that shortening sample than those of the fresh shortening or chicken fat. Results clearly demonstrated that the FFA values were a useful parameter for measuring the extent of shortening usage for the chicken frying operation.
Breast lipid
23.1
5.8
.4 9.6 0
9.2 54.2 11.1
18.5 67.0 4.5
4.4 43.2 20.3
1.2 7.5
REFERENCES American Oil Chemists' Society, 1973. Official Methods of Analysis. 5th ed. Am. Oil Chem. Soc, Chicago, IL. Hornstein, I., J. A. Alford, L. E. Elliott, and P. F. Crowe, 1960. Determination of free fatty acids in fat. Anal. Chem. 32:540-541. Kawada, T., T. G. Krishnamurthy, B. D. Mookherjee, and S. S. Chang, 1967. Chemical reactions involved in the deep fat frying of foods. II. Identification of acidic volatile decomposition products of corn oil. J. Am. Oil Chem. Soc. 44:131-135. Marion, J. E., and J. G. Woodroff, 1963. The fatty acid composition of breast, thigh, and skin tissue of chicken broilers as influenced by dietary fats. Poultry Sci. 42:1202-1207. Perkins, E. G., 1967. Formation of non-volatile decomposition products in heated fats and oils. Food Technol. 21:611-616. Swern, D., 1976. Bailey's Industrial Oil and Fat Products. 3rd ed. Intersci. Publ., NY. Weiss, T. J., 1970. Food Oils and Their Uses. Avi Publ. Co., Westport, CT. Yang, C. S., and T. C. Chen, 1980. Effect of oven holding on qualities of fried chicken parts. J. Food Sci. 45:635-637.
Downloaded from http://ps.oxfordjournals.org/ at University of Saskatchewan Library on June 18, 2015
1.1
16 0 16 1
Fresh shortening
1984 Poultry Science 63:1467-1469 INTRODUCTION
Deep-fat fried chicken parts are sought and accepted by consumers of all ages. Many factors affect the quality of fried chicken products, and the frying medium is a major one. During the deep-fat frying process, the shortening is repeatedly used at elevated temperatures in the presence of air, water, breading compounds, and chicken parts. Under such conditions, the quality of frying medium deteriorates due to hydrolysis, oxidation, and polymerization reactions. Free fatty acids (FFA) are formed during frying as a result of cleavage and oxidation of double bonds (Perkins, 1967) and as a result of "hydrolysis" during the presence of moisture (Weiss, 1970). According to Weiss (1970), the FFA content of a fat is a good indicator of overall quality. The FFA in vegetable oils are the result of the hydrolysis of fats, and the hydrolysis is greatly accelerated by lipase. Kawada et al. (1967) suggested that acidic volatile products may be produced from triglycerides of corn oil during deep fat frying through hydrolysis of the ester linkages, oxidation of longer chain fatty acids, thermal degradation of esters, thermal oxidation of an a-carbon atom of the acid in triglycerides, and an autoxidation of aldehydes and ketones. Kawada et al. (1967) also reported that during the early stage of frying acidic
'Journal Paper No. 5804 of the Mississippi Agricultural and Forestry Experiment Station.
decomposition products are predominantly produced by hydrolysis of triglycerides. The purpose of this study was to investigate the accumulation of FFA in shortening during the chicken frying operation. MATERIALS AND METHODS The cooperation of two commercial fried chicken outlets was obtained. At the beginning of this investigation, the same brand of fresh shortening (pure vegetable frying shortening, NIFDA, GA) was used in their fryers (JCP Frialator, J. C. Pitman & Sons, Inc., NH). The coating ingredients and methods of the fried chicken preparation were also the same. Eightpiece cut broiler parts from 908- to 1135-g carcasses were flour predusted, dipped in a batter, and floured again before being fried at 168 C for 12 min (Yang and Chen, 1980). The amount of raw chicken parts fried, as well as the quantity of shortening added to replenish the fryer, were recorded daily for 12 days. At the end of each day's frying operation, the shortening was filtered and approximately 250 ml of shortening was sampled from each fryer in covered glass jars and held at 2 to 4 C. The collected samples were transported to the laboratory at the end of the sample collection period for analyses. During the investigation period, except for the chicken parts, no other food item was fried in the shortening. Before analyses, the shortening samples were melted at 50 C and mixed individually. The FFA content of the samples was measured according to the procedures described in
1467
Downloaded from http://ps.oxfordjournals.org/ at University of Saskatchewan Library on June 18, 2015
ABSTRACT The cooperation of two commercial fried chicken outlets was obtained. After 12 days of operation, 1246 and 1062 kg of raw chicken parts had been fried at Outlets A and B, respectively. The free fatty acid-(FFA) values of the shortening samples increased continuously throughout the observation period, and the increase was .11 and .25%/100 kg of raw chicken parts fried for Outlets A and B, respectively. In general, the increase of each individual fatty acid appeared to be linear to the quantity of chicken parts fried except for the palmitoleic acid. More than half of the FFA found in the shortening samples were oleic acid. (Key words: chicken frying, free fatty acids)
1468
CHEN
detector. A 183.9 X .64 cm copper column packed with 15% diethylene glycol succinate and 3% phosphoric acid as liquid phase and Chromosorb "W" as solid support was used. The fatty acids were identified by comparing the retention values of unknown peaks with fatty acid standards. UJ e~
RESULTS AND DISCUSSION
< >
4 8 12 PARTS FRIED (X\00kg) FIG. 1. Free fatty acid value of shortening as affected by chicken frying, o, Outlet A; •, Outlet B.
Official Methods of Analysis (American Oil Chemists' Society, 1973) The FFA profiles of the 4, 8, and 12 day's shortening samples were analyzed according to the methods described by Hornstein et al. (1960). Fatty acid composition of broiler breast meat lipid from the ether extraction of oven dried breast meat, along with the fresh shortening samples, was also determined as described by Marion and Woodroff (1963). The fatty acid methylates were analyzed with a Beckman GC-45 gas chromatograph equipped with flame ionization
TABLE 1. Accumulation of free fatty acids (FFA) in shortening during chicken frying1 Shortening sample source: Sampling day: Chicken parts fried, kg: FFA, V As % oleic acid:
A 4 323
8 809
B 12
1.21
1.72
1246 2.24
2.11 27.00 9.06 24.00 109.00 20.00
3.11 62.09 9.63 46.91 234.55 51.88
4.36 91.64 23.38 63.07 279.27 78.54
4 475
8 733
12
1.20
1.75
1062 2.70
2.62 50.70 13.11 37.05 174.65 40.95
3.09 62.03 15.15 44.34 216.67 46.46
3.90 89.90 25.65 47.03 265.56 61.76
Fatty acid/17:0 14 16 16 18 18 18 1
0 0 1 0 1 2
Mean of three determinations.
Downloaded from http://ps.oxfordjournals.org/ at University of Saskatchewan Library on June 18, 2015
If I
After 12 days of operation, 1246 and 1062 kg of raw chicken parts were fried at fried chicken Outlets A and B, respectively. The average amount of fresh shortening replenished during the frying operation was 7 kg/100 kg of raw parts. Free fatty acid values of the shortening samples from both outlets increased continuously throughout the observation period (Fig. 1). The increase in FFA values were .11 and .25%/100 kg of raw chicken parts fried for Outlets A and B, respectively. These values were obtained from the slope of the lines in Figure 1. Results indicated that the FFA content of shortening could be an indicator for determining the extent of the shortening usage in frying chicken operation. The FFA content correlated with the smoking point of the frying medium, (Swern, 1976); an oil with a fatty acid content of .7% had a smoke point of 168 C or higher and one with a free fatty acid content of .4% had a smoke point of 176 C or higher. It is of interest to note that although the FFA content of the used chicken frying shortening was high, no problem related to smoke point was observed when the shortening was heated at 168 C.
RESEARCH NOTE
1469
TABLE 2. Percent fatty acid content of chicken frying shortening and chicken breast meat lipid Sh ortening A
Sample source: Chicken parts fried, kg: Fatty acids 14:0
323
809
Shortening B 1246
475
733
1062
1.4
1.7
1.2
1.2
1.4
15.0
17.8
18.6
16.0
16.5
18.0
3.6
6.1
6.3
5.4
5.4
18 0 18 1 18 2
11.8 56.4 12.1
11.3 51.2 12.2
11.1 50.7 11.6
12.3 55.5 9.7
11.4 54.2 11.3
By calculating against the internal standard, relative concentrations of each individual FFA were summarized in Table 1. In general, the increase of each individual fatty acid appeared to be linear to the quantity of raw chicken parts fried except for the palmitoleic (16:1) acid and the oleic (18:1) acid from Source A samples. More than half of the FFA found in the used frying shortening samples were 18:1 fatty acid. The fatty acid composition of the used shortening samples represents a mixture of fresh shortening and the chicken fat (Table 2). It is of interest to note that the composition of the FFA in used shortening was closer to the fatty acid composition of that shortening sample than those of the fresh shortening or chicken fat. Results clearly demonstrated that the FFA values were a useful parameter for measuring the extent of shortening usage for the chicken frying operation.
Breast lipid
23.1
5.8
.4 9.6 0
9.2 54.2 11.1
18.5 67.0 4.5
4.4 43.2 20.3
1.2 7.5
REFERENCES American Oil Chemists' Society, 1973. Official Methods of Analysis. 5th ed. Am. Oil Chem. Soc, Chicago, IL. Hornstein, I., J. A. Alford, L. E. Elliott, and P. F. Crowe, 1960. Determination of free fatty acids in fat. Anal. Chem. 32:540-541. Kawada, T., T. G. Krishnamurthy, B. D. Mookherjee, and S. S. Chang, 1967. Chemical reactions involved in the deep fat frying of foods. II. Identification of acidic volatile decomposition products of corn oil. J. Am. Oil Chem. Soc. 44:131-135. Marion, J. E., and J. G. Woodroff, 1963. The fatty acid composition of breast, thigh, and skin tissue of chicken broilers as influenced by dietary fats. Poultry Sci. 42:1202-1207. Perkins, E. G., 1967. Formation of non-volatile decomposition products in heated fats and oils. Food Technol. 21:611-616. Swern, D., 1976. Bailey's Industrial Oil and Fat Products. 3rd ed. Intersci. Publ., NY. Weiss, T. J., 1970. Food Oils and Their Uses. Avi Publ. Co., Westport, CT. Yang, C. S., and T. C. Chen, 1980. Effect of oven holding on qualities of fried chicken parts. J. Food Sci. 45:635-637.
Downloaded from http://ps.oxfordjournals.org/ at University of Saskatchewan Library on June 18, 2015
1.1
16 0 16 1
Fresh shortening