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The Influence of Brine Chilling on Tenderness of Hot-Boned, Chill-Boned, and Age-Boned Broiler Breast Fillets1
The Influence of Brine Chilling on Tenderness of Hot-Boned, Chill-Boned, and Age-Boned Broiler Breast Fillets1 A. R. SAMS and D. M. JANKY2 Institute of Food and Agricultural Sciences, Department of Poultry Science, University of Florida, Gainesville, Florida 32611 (Received for publication October 28, 1985)
INTRODUCTION Current marketing strategies used in the food industry encourage processors of poultry and other foods to differentiate their particular product from that of their competitors by using unique packaging and branding of the product. This type of marketing strategy, however, requires a high degree of uniformity in the quality attributes of the product. Many poultry processors have been producing boned meat products, especially breast fillets, for use in both the institutional and retail marketplace. These fillets are normally harvested from the ready-to-cook carcass as soon after chilling as possible to save labor and handling costs as well as storage space. Consumer response, however, has indicated that this practice often results in less than optimum meat tenderness in the finished product (Goodwin, 1984). Research has shown that 3 to 6 hr of postmortem aging prior to breast muscle removal is required for adequate tenderness development (de Fremery and Pool, 1959;
1 Florida Agricultural Experiment Stations Journal Series No. 6834. 2 To whom correspondence should be addressed.
Dodge and Stadelman, 1959; Stewart et al, 1984a; Lyon et al, 1985). It has been suggested that fillet harvesting could be accomplished even earlier in the processing sequence with an even greater reduction in labor, energy, and total production costs (Hamm, 1981). However, this procedure, known as hot boning, has been shown to increase meat toughness dramatically (Lowe, 1948; Pool et al, 1959; Lyon et al, 1973, 1985; Stewart et al, 1984a). In order for the poultry industry to continue using immediate postchill boning or initiate hot-boning procedures for fillet harvesting, it will be necessary to develop methodology to minimize both absolute toughness and nonuniformity of tenderness. One approach to this problem might involve the addition of sodium chloride or other salts to the chilling medium. A large amount of research, reviewed by Dukes and Janky (1984), has shown that the addition of sodium chloride to the chill solution, under restrictions of commercial times and temperatures, increased tenderness of breast meat from conventionally processed, aged broiler carcasses. The purpose of this research was to determine the effect of brine chilling on tenderness and other physical characteristics of broiler
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ABSTRACT Fillets (pectoralis superficialis) were harvested from broiler carcasses immediately after picking (hot boned), immediately after chilling (chill boned), or after a 24-hr aging period (age boned). Hot-boned fillets and all carcasses were equally distributed within two chilling solutions; tap water or 5% sodium chloride solution. The pH at the time of boning was ascertained for all fillets. Battered, breaded, deep-fat fried fillets were analyzed for shear force, percent chloride ion, and moisture and sodium concentration. Boning time produced the greatest effect on tenderness of broiler breast meat, with tenderness improving as the length of time between slaughter and boning was increased. Brine chilling improved tenderness of hot-boned fillets to the same level as that observed for fillets harvested from carcasses immediately after chilling but had no effect on fillets harvested postchill or after aging. Improvement in tenderness of brine-chilled, hot-boned fillets could not be explained on the basis of pH or water-holding capacity but was related to higher tissue chloride ion concentration. (Key words: tenderness, brine, salt, boning time, fillet) 1986 Poultry Science 65:1316-1321
BRINE CHILLING AND BONING TIME
breast fillets harvested imemdiately after picking (hot boned), immediately after chilling (chill boned), or after 24 hr of aging (age boned). MATERIALS AND METHODS
with small amounts of crushed ice. A chilling medium to carcass/fillet ratio of 3.5:1 (w/w) and an ice to chilling medium ratio of 1:9, or less, were maintained. Ice was present at all times in 1-C solutions only. After chilling, fillets and carcasses were rinsed with tap water, drained (10 min), and weighed to determine water uptake during chilling. Equal representation from each processing group was maintained as fillets were immediately harvested from four carcasses from each chill treatment (chill boned), identified, and sampled for pH as described for hot-boned fillets. All fillets and the remaining carcasses were packed in crushed ice and held for 24 hours at 2 C. Following the aging period, fillets were harvested from the remaining carcasses, identified, and sampled for pH as previously described. These procedures produced 4 paired fillet samples from each boning time and chilling solution combination within each of the four chilling replications. After wing removal from all fillet pairs, fillets were packaged in pairs in labeled heat-sealable plastic pouches, placed in Cryovac® bags, frozen, and stored (maximum = 2 weeks) at —18 C for further analysis. Individual liquid nitrogen-frozen samples were wrapped in butcher paper, pulverized with a hammer, and mixed for 30 sec at a ratio of 1:10 (w/v) with a .005 M solution of sodium iodoacetate, using a medium-high speed in a Virtis® mixer. The pH of this solution was then read on a Corning® pH meter. Fillets were thawed (48 hr, 2 C) by chilling replicate, individually identified, battered with unseasoned batter (Komarik et al, 1974), breaded (Martha White All Purpose White Flour®), and deep-fat fried in an open deep-fat fryer for 8 min at 163 C. Cooked fillets were cooled at room temperature and then stored in aluminum foil lined and covered pans at 2 C overnight. After batter and breading removal, two samples (40 X 20 X 5 mm) from the anterior and medial portion of each cooked fillet were removed and sheared using a Food Technology Corporation Texture Test System® according to procedures described by Dukes and Janky (1984). The resulting four values/pair of fillets were averaged to determine a mean shear force value for each carcass represented. Remaining fillet samples were composited by treatment within a chilling replicate by chopping the meat to a uniform texture in a silent cutter. Each
Downloaded from http://ps.oxfordjournals.org/ at University of Bath, Library on June 19, 2015
Cobb feather-sexed male broilers were reared on litter-covered floor pens and fed a commercial-type, corn-soy diet. At 56 days of age, 96 broilers were selected within a weight range of 1800 to 2300 g, cooped (8 birds/coop), and held for 12 to 16 hr. Broilers were slaughtered using electrical stunning and exsanguination techniques in groups of 12 birds to ensure uniformity in time interval between slaughter and boning. Broilers were subscalded (60 C, 45 sec) and picked in a rotary drum picker (25 sec) by group. Breast fillets (pectoralis superficialis) with wings attached were harvested using the method of Hamm (1981) from four carcasses from each group immediately after picking (hot boned). The fillets from each carcass were wired together (at the wing) and identified. The posterior 2.54-cm portion of each fillet was removed, placed together in an identified Whirl Pac® bag, and frozen in liquid nitrogen for later pH analysis. At the same time, the remaining eight carcasses were eviscerated and, after rinsing, individual weights were obtained for all carcasses and paired fillets. Carcasses and fillets were held at room temperature until an additional 12-bird group had been treated as above, then chilled as a 24-fillet/carcass chilling replicate. Using this technique, no more than 15 min elapsed between death of the animal and chilling. This resulted in four chilling replicates of 24 fillet/carcasses each. Four paired fillets and eight carcasses from each chilling replicate (two paired fillets and four carcasses from each processing group) were chilled in either a 5% sodium chloride solution (w/w) or tap water. Chilling involved a two-step temperature reduction of 30 min at 21 C followed by 30 min at 1 C and continuous manual agitation of the chill solutions by oscillation of the chilling drums. This resulted primarily in water movement; however, some carcass movement also occurred. Brine concentration was maintained at a specific gravity of 1.035 ± .005 with cold, saturated sodium chloride solution. Chill solution temperatures were monitored with a recording potentiometer equipped with copper constantan thermocouples and adjusted
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SAMS AND JANKY
RESULTS AND DISCUSSION
Regardless of the chilling media, hot-boned fillets absorbed or adsorbed significantly more solution than carcasses (Table 1). This was expected because of the increased surface area per unit weight of a smaller fillet over a larger whole carcass. In addition, the cut surface of the fillet would have been more receptive to the chilling solution than the uncut muscle of the carcass, covered with skin and, for some muscles, partially covered with bone. Brinechilled, hot-boned fillets had a significantly lower brine/water uptake than that observed for hot-boned fillets chilled in tap water (Table 1). Osmotic pressure of the salt solution on the
TABLE 1. Water or brine uptake of chilled broiler carcasses boned after chilling or aging and water or brine uptake of chilled fillets removed from hot carcasses Treatment Chill medium
Hot boned
Chill boned
Age boned
Water Brine
5.5 a 4.7t>
2.3 d 3.2C
2.4 d 3.4C
Means with different superscripts are significantly different (P«.05).
fully exposed breast muscle might account for this difference. Chilled carcasses did not differ in water or brine uptake based on time of fillet removal; however, uptake of chill media was significantly higher for carcasses chilled in salt solution than for carcasses chilled in water (Table 1). The enhancement of brine uptake for carcasses chilled in salt solution has been documented and discussed by Hoey et al. (1983) and Dukes and Janky (1984). Significant differences in water or brine uptake have been observed only when sampled carcasses were uniform in size. This uniformity allows small mean differences in uptake to be significant because of the relative lack of variation in this parameter under these conditions. Breast muscle pH at time of boning was not affected by the chilling media but was significantly decreased as the interval from slaughter to time of boning was increased (Table 2). These data were consistent with previous findings reported by Stewart et al. (1984a,b) for excised broiler breast muscle sampled at similar time intervals postmortem. Shear values of water-chilled fillets or fillets harvested from water-chilled carcasses significantly decreased as the time interval between slaughter and fillet removal was increased (Table 2). Values observed were similar to those reported by Stewart et al. (1984a) for broiler breast muscle excised at similar time intervals postmortem. When brine was used as the chilling medium, shear values for hot-boned and chill-boned fillets were not significantly different. However, shear values of age-boned fillets were significantly lower than those observed for fillets harvested at earlier times. Within boning times, brine chilling had no significant effect on shear values of fillets harvested from carcasses after either chilling or aging (Table 2) but significantly reduced shear values of hot-boned fillets to the same level as that observed for fillets harvested from chilled carcasses. Shear force values resulting from either brine chilling of hot-boned fillets or delaying fillet harvest until after carcass chilling indicated that the meat would have been judged as "tough" by the consumer. Simpson and Goodwin (1974) reported that chicken meat with a shear value of 8.0 kg force/g sample or higher was judged "tough" by sensory panelists. The variance associated with the shear value mean for age-boned, water-chilled fillets was significantly smaller than the variance asso-
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composite was analyzed, in duplicate, for moisture content (AOAC, 1970), chloride ion content (AOAC, 1970, Volhard method), and sodium concentration (Shirley et al, 1973). The entire experiment was twice repeated, producing a total of three trials. Data other than shear force values were analyzed by analysis of variance and Duncan's multiple range test procedures (Steel and Torrie, 1980) using programs available in the Statistical Analysis System (SAS, 1982). Shear force data means were tested for unequal variances using an F' (folded) statistic (Steel and Torrie, 1980) and significance of differences between means was determined with a " t " test statistic that uses Satterthwaite's approximation for testing means with unequal variances (Satterthwaite, 1946). Shear force and pH data were tested for correlation (SAS, 1982). Because no significant trial X treatment interactions were observed, data from all three trials were pooled.
BRINE CHILLING AND BONING TIME
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TABLE 2. Breast muscle pH at time of boning, shear force of cooked fillets, and the correlation between these parameters for fillets removed from hot carcasses and either water or brine chilled and fillets removed from chilled or aged, water- or brine-chilled carcasses1
Parameter
Chilling medium
Hot boned 6.41a 6.42a
Chill boned
Age boned
6.16 b 6.27 a b
5.79 c 5.83 c
Water Brine
Shear force, kg force/g
Water Brine
10.2a 8.8b
8.0 b 8.5 b
5.4C 4.9 C
Correlation, r
Water Brine
-.24 -.05
.21 .24
-.02 -.27
a—d Means within a parameter, across both chilling media, with different superscripts are significantly different (P«.05). 1 n=48.
dated with the shear value means associated with hot-boned fillets, regardless of chilling solution, and the variance associated with the shear value mean for age-boned, brine-chilled fillets was significantly smaller than that associated with any of the other shear value means (data not shown). Janky et al. (1982) observed that tenderness was improved (lower shear values) by brine soaking broiler carcass halves, but that the degree of tenderization effect was reduced as the initial tenderness level of the treated substrate was decreased. In the present experiment, it appeared that both aging and brine chilling decreased the natural variation in tenderness of the sampled population. This could have important ramifications in instances where a tight restriction on tenderness variation is required, such as the production of breast fillets for individual segments of the fast food industry. A significant tenderization effect of brine chilling on meat from aged carcasses has been documented (Janky etal., 1978, 1983;Hoeye£ al, 1983; Dukes and Janky, 1984, 1985) for a variety of chilling procedures. The only major procedural difference between these studies and the one herein reported was the use of deep-fat frying as the cooking method instead of baking. It was hypothesized that the difference in cooking method accompanied by the tendency of brine chilling to reduce sample variation masked the tenderization effect of brine chill-
ing on already tender, age-boned fillets. The lack of a tenderness effect due to brine chilling for chill-boned fillets might also be due to the above hypothesis. Correlation of shear force with pH at time of boning was not significant within any individual boning time-chill solution combination (Table 2); however, correlations over the entire experiment or within a chill solution were positive and significant (data not shown). This agreed with conclusions drawn by Stewart et al. (1984a) that pH and tenderness of meat are related to physiological changes in the muscle postmortem as a function of time but do not necessarily have a cause and effect relationship. As expected, chloride and sodium concentration in cooked fillets was significantly increased by brine chilling, regardless of boning time (Table 3). The additional sodium content would not pose a large problem, commercially, because most of the fillet-type product is destined for institutional uses such as fast-food outlets. In these situations, the sodium chloride level of the batter and breading mixes could be adjusted so that overall sodium content for these types of products would not be increased. Other chloride salts might also be substituted for sodium chloride in the chilling media (Palladino and Ball, 1979; Hoey et al, 1983; Sams et al, 1986). Hot-boned fillets, brine chilled as fillets, had significantly higher sodium and chloride levels in the cooked meat than
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pH
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SAMSANDJANKY TABLE 3. Chloride, sodium, and moisture contents of cooked fillets removed from hot carcasses and either water or brine chilled andfilletsremoved from chilled or aged, water- or brine-chilled carcasses
Parameter
Chilling medium
Hot boned
Treatment Chill boned .llc .16 b
Age boned
Water Brine
.llc .31 a
.10 c .17 b
Sodium, mg/100 g
Water Brine
85.7 cd 236. l a
93.7= 125.3b
78.1 d 129.5b
Moisture, %
Water Brine
64.0a 64.0a
64.4a 64.5a
64.5 a 64.5 a
Means within a parameter, across both chilling media, with different superscripts are significantly different (P=S.05).
fillets removed from chilled or aged carcasses (Table 3). These data were consistent with differences in brine uptake between fillets and carcasses previously discussed. Sodium levels of cooked meat from water-chilled samples were somewhat higher and more variable than expected; however, chloride levels were consistent with normal values for chicken light meat(USDA, 1979). The chloride ion has been associated with the tenderization effect of brine chilling (Janky et al., 1983; Palladino and Ball, 1979; Hoey et al., 1983). Janky et al. (1983) observed maximum tenderization of brine-chilled broiler breast meat when raw tissue chloride levels were between .75 and 1.0%; however, the minimum or threshold concentration required to produce the tenderization effect has not been determined. In the present experiment, chloride levels of postchill harvested fillets from brinechilled carcasses were very low by comparison with chloride levels of the hot-boned, brinechilled fillets and might have been below the threshold level required to produce a tenderization effect. Percent moisture of cooked meat samples was not affected by boning time or chilling medium (Table 3). Janky et al. (1983) related the tenderization effect of brine chilling to chloride-induced increases in cooked meat moisture or water-holding capacity. In the present study, this type of relationship was not found. The tenderization effect of brine chilling
was evident with hot-boned fillets; however, water content was not different. Brine chilling may also improve tenderness through interference with the normal mechanism of rigor development by precipitating calcium ions released from the sarcoplasmic reticulum as calcium chloride. In conclusion, boning time produced the greatest effect on tenderness of broiler breast meat with tenderness improving as the length of time between slaughter and boning was increased. Brine chilling improved tenderness of hot-boned fillets to the same level as that observed for fillets harvested from carcasses immediately after chilling but had no effect on average shear force of fillets harvested postchill or after aging. Improvement in tenderness of brine-chilled, hot-boned fillets could not be explained on the basis of pH or water holding capacity but was related to higher tissue chloride ion concentration. REFERENCES Association of Official Analytical Chemists, 1970. Official Methods of Analysis. 10th ed. Assoc. Offic. Anal. Chem., Washington, DC. de Fremery, D., and M. F. Pool, 1959. Rate of rigor mortis development in relation to tenderness of chicken muscle. Poultry Sci. 38:1180-1181. Dodge, J. W., and W. J. Stadelman, 1959. Post mortem aging of poultry meat and its effect on the tenderness of breast muscles. Food Technol. 13:81 — 84. Dukes, M. G., and D. M. Janky, 1984. Physical characteristics of pectoralis superficialis from broiler
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Chloride, %
BRINE CHILLING AND BONING TIME
cooked yield and tenderness of cut up broiler parts. Poultry Sci. 52:1103-1111. Palladino, D. K., and H. R. Ball, Jr., 1979. Effects of selected inorganic salts on certain tenderness characteristics of spent hen muscle. J. Food Sci. 44:322-326. Pool, M. F., D. de Fremery, A. A. Campbell, and A. A. Klose, 1959. Poultry tenderness. II. Influences of processing on tenderness of chickens. Food Technol. 13:25-29. Sams, A. R., M. G. Dukes, and D. M. Janky, 1986. Tenderness and sensory evaluation of pectoralis superficialis from broilers chilled in potassium chloride, sodium chloride, or Neobakasal® salt substitute. Poultry Sci. 6 5 : 7 3 8 - 7 4 1 . SAS Institute, Inc., 1982. SAS User's Guide: Statistics. SAS Inst., Cary, NC. Satterthwaite, F. W., 1946. An approximate distribution of estimates of variance components. Biometrics Bull. 2:110-114. Shirley, R. L., J. F. Easley, J. P. Feaster, C. B. Ammerman, and J. E. Moore, 1973. Atomic Absorption Spectrophotometry. In Equipment and Procedures, 4th ed. University of Florida, Gainesville, FL. Simpson, M. D., and T. L. Goodwin, 1974. Comparison between shear values and taste panel scores for predicting tenderness of broilers. Poultry Sci. 53:2042-2046. Steel, R.G.D., and J. H. Torrie, 1980. Principles and Procedures of Statistics, 2nd ed., McGraw-Hill Book Co., New York, NY. Stewart, M. K., D. L. Fletcher, D. Hamm, and J. E. Thomson, 1984a. The influence of hot boning broiler breast muscle on pH decline and toughening. Poultry Sci. 63:1935-1939. Stewart, M. K., D. L. Fletcher, D. Hamm, and J. E. Thomson, 1984b. The effect of hot boning broiler breast meat muscle on postmortem pH decline. Poultry Sci. 63:2181-2186. United States Department of Agriculture, 1979. Composition of Foods: Poultry Products, RawProcessed-Prepared. Agric. Handbook No. 8-5. USDA Sci. Educ. Admin., Washington, DC.
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carcasses chilled in either water or sodium chloride solutions under commercial conditions. J. Food Sci. 4 9 : 8 4 9 - 8 5 1 , 858. Dukes, M. G., and D. M. Janky, 1985. Physical characteristics and sensory evaluation of cooked pectoralis superficialis from broiler carcasses chilled in water or brine solutions under commercial time and temperature conditions. Poultry Sci. 64:664-668. Goodwin, T. L., 1984. It takes tough discipline to make tender chicken! Broiler Ind. 47(9):43—44. Hamm, D., 1981. Unconventional meat harvesting. Poultry Sci. 60:1666. (Abstr.) Hoey, J. M., M. G. Dukes, and D. M. Janky, 1983. Tenderness of pectoralis superficialis from broilers chilled in potassium or sodium chloride ice slush. J. Food Sci. 48:675-676. Janky, D. M., A. S. Arafa, J. L. Oblinger, J. A. Koburger, and D. L. Fletcher, 1978. Sensory, physical, and microbiological comparison of brine-chilled, water-chilled, and hot-packaged (no chill) broilers. Poultry Sci. 57:417-421. Janky, D. M., M. D. Carpenter, D. L. Fletcher, A. S. Arafa, J. A. Koburger, and R. L. West, 1983. Physical characteristics of pectoralis superficialis from brine-chilled broiler carcasses. Poultry Sci. 62:433-436. Janky, D. M., J. A. Koburger, and J. L. Oblinger, 1982. A comparison of brined and unbrined paired broiler carcass-halves for tenderness. Poultry Sci. 6 1 : 7 1 6 - 7 1 8 . Komarik, S. L., D. K. Tressler, and L. Long, 1974. Page 240 in Food Products Formulary: Meats, Poultry, Fish, Shellfish. AVI Publishing Co., Westport, CT. Lowe, B., 1948. Factors affecting the palatability of poultry with emphasis on histological postmortem changes. Adv. Food Res. 1:203—256. Lyon, C. E., D. Hamm, and J. E. Thomson, 1985. pH and tenderness of broiler breast meat deboned various times after chilling. Poultry Sci. 64:307— 310. Lyon, C. E., B. G. Lyon, and J. P. Hudspeth, 1973. The effect of different cutting procedures on the
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INTRODUCTION Current marketing strategies used in the food industry encourage processors of poultry and other foods to differentiate their particular product from that of their competitors by using unique packaging and branding of the product. This type of marketing strategy, however, requires a high degree of uniformity in the quality attributes of the product. Many poultry processors have been producing boned meat products, especially breast fillets, for use in both the institutional and retail marketplace. These fillets are normally harvested from the ready-to-cook carcass as soon after chilling as possible to save labor and handling costs as well as storage space. Consumer response, however, has indicated that this practice often results in less than optimum meat tenderness in the finished product (Goodwin, 1984). Research has shown that 3 to 6 hr of postmortem aging prior to breast muscle removal is required for adequate tenderness development (de Fremery and Pool, 1959;
1 Florida Agricultural Experiment Stations Journal Series No. 6834. 2 To whom correspondence should be addressed.
Dodge and Stadelman, 1959; Stewart et al, 1984a; Lyon et al, 1985). It has been suggested that fillet harvesting could be accomplished even earlier in the processing sequence with an even greater reduction in labor, energy, and total production costs (Hamm, 1981). However, this procedure, known as hot boning, has been shown to increase meat toughness dramatically (Lowe, 1948; Pool et al, 1959; Lyon et al, 1973, 1985; Stewart et al, 1984a). In order for the poultry industry to continue using immediate postchill boning or initiate hot-boning procedures for fillet harvesting, it will be necessary to develop methodology to minimize both absolute toughness and nonuniformity of tenderness. One approach to this problem might involve the addition of sodium chloride or other salts to the chilling medium. A large amount of research, reviewed by Dukes and Janky (1984), has shown that the addition of sodium chloride to the chill solution, under restrictions of commercial times and temperatures, increased tenderness of breast meat from conventionally processed, aged broiler carcasses. The purpose of this research was to determine the effect of brine chilling on tenderness and other physical characteristics of broiler
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Downloaded from http://ps.oxfordjournals.org/ at University of Bath, Library on June 19, 2015
ABSTRACT Fillets (pectoralis superficialis) were harvested from broiler carcasses immediately after picking (hot boned), immediately after chilling (chill boned), or after a 24-hr aging period (age boned). Hot-boned fillets and all carcasses were equally distributed within two chilling solutions; tap water or 5% sodium chloride solution. The pH at the time of boning was ascertained for all fillets. Battered, breaded, deep-fat fried fillets were analyzed for shear force, percent chloride ion, and moisture and sodium concentration. Boning time produced the greatest effect on tenderness of broiler breast meat, with tenderness improving as the length of time between slaughter and boning was increased. Brine chilling improved tenderness of hot-boned fillets to the same level as that observed for fillets harvested from carcasses immediately after chilling but had no effect on fillets harvested postchill or after aging. Improvement in tenderness of brine-chilled, hot-boned fillets could not be explained on the basis of pH or water-holding capacity but was related to higher tissue chloride ion concentration. (Key words: tenderness, brine, salt, boning time, fillet) 1986 Poultry Science 65:1316-1321
BRINE CHILLING AND BONING TIME
breast fillets harvested imemdiately after picking (hot boned), immediately after chilling (chill boned), or after 24 hr of aging (age boned). MATERIALS AND METHODS
with small amounts of crushed ice. A chilling medium to carcass/fillet ratio of 3.5:1 (w/w) and an ice to chilling medium ratio of 1:9, or less, were maintained. Ice was present at all times in 1-C solutions only. After chilling, fillets and carcasses were rinsed with tap water, drained (10 min), and weighed to determine water uptake during chilling. Equal representation from each processing group was maintained as fillets were immediately harvested from four carcasses from each chill treatment (chill boned), identified, and sampled for pH as described for hot-boned fillets. All fillets and the remaining carcasses were packed in crushed ice and held for 24 hours at 2 C. Following the aging period, fillets were harvested from the remaining carcasses, identified, and sampled for pH as previously described. These procedures produced 4 paired fillet samples from each boning time and chilling solution combination within each of the four chilling replications. After wing removal from all fillet pairs, fillets were packaged in pairs in labeled heat-sealable plastic pouches, placed in Cryovac® bags, frozen, and stored (maximum = 2 weeks) at —18 C for further analysis. Individual liquid nitrogen-frozen samples were wrapped in butcher paper, pulverized with a hammer, and mixed for 30 sec at a ratio of 1:10 (w/v) with a .005 M solution of sodium iodoacetate, using a medium-high speed in a Virtis® mixer. The pH of this solution was then read on a Corning® pH meter. Fillets were thawed (48 hr, 2 C) by chilling replicate, individually identified, battered with unseasoned batter (Komarik et al, 1974), breaded (Martha White All Purpose White Flour®), and deep-fat fried in an open deep-fat fryer for 8 min at 163 C. Cooked fillets were cooled at room temperature and then stored in aluminum foil lined and covered pans at 2 C overnight. After batter and breading removal, two samples (40 X 20 X 5 mm) from the anterior and medial portion of each cooked fillet were removed and sheared using a Food Technology Corporation Texture Test System® according to procedures described by Dukes and Janky (1984). The resulting four values/pair of fillets were averaged to determine a mean shear force value for each carcass represented. Remaining fillet samples were composited by treatment within a chilling replicate by chopping the meat to a uniform texture in a silent cutter. Each
Downloaded from http://ps.oxfordjournals.org/ at University of Bath, Library on June 19, 2015
Cobb feather-sexed male broilers were reared on litter-covered floor pens and fed a commercial-type, corn-soy diet. At 56 days of age, 96 broilers were selected within a weight range of 1800 to 2300 g, cooped (8 birds/coop), and held for 12 to 16 hr. Broilers were slaughtered using electrical stunning and exsanguination techniques in groups of 12 birds to ensure uniformity in time interval between slaughter and boning. Broilers were subscalded (60 C, 45 sec) and picked in a rotary drum picker (25 sec) by group. Breast fillets (pectoralis superficialis) with wings attached were harvested using the method of Hamm (1981) from four carcasses from each group immediately after picking (hot boned). The fillets from each carcass were wired together (at the wing) and identified. The posterior 2.54-cm portion of each fillet was removed, placed together in an identified Whirl Pac® bag, and frozen in liquid nitrogen for later pH analysis. At the same time, the remaining eight carcasses were eviscerated and, after rinsing, individual weights were obtained for all carcasses and paired fillets. Carcasses and fillets were held at room temperature until an additional 12-bird group had been treated as above, then chilled as a 24-fillet/carcass chilling replicate. Using this technique, no more than 15 min elapsed between death of the animal and chilling. This resulted in four chilling replicates of 24 fillet/carcasses each. Four paired fillets and eight carcasses from each chilling replicate (two paired fillets and four carcasses from each processing group) were chilled in either a 5% sodium chloride solution (w/w) or tap water. Chilling involved a two-step temperature reduction of 30 min at 21 C followed by 30 min at 1 C and continuous manual agitation of the chill solutions by oscillation of the chilling drums. This resulted primarily in water movement; however, some carcass movement also occurred. Brine concentration was maintained at a specific gravity of 1.035 ± .005 with cold, saturated sodium chloride solution. Chill solution temperatures were monitored with a recording potentiometer equipped with copper constantan thermocouples and adjusted
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SAMS AND JANKY
RESULTS AND DISCUSSION
Regardless of the chilling media, hot-boned fillets absorbed or adsorbed significantly more solution than carcasses (Table 1). This was expected because of the increased surface area per unit weight of a smaller fillet over a larger whole carcass. In addition, the cut surface of the fillet would have been more receptive to the chilling solution than the uncut muscle of the carcass, covered with skin and, for some muscles, partially covered with bone. Brinechilled, hot-boned fillets had a significantly lower brine/water uptake than that observed for hot-boned fillets chilled in tap water (Table 1). Osmotic pressure of the salt solution on the
TABLE 1. Water or brine uptake of chilled broiler carcasses boned after chilling or aging and water or brine uptake of chilled fillets removed from hot carcasses Treatment Chill medium
Hot boned
Chill boned
Age boned
Water Brine
5.5 a 4.7t>
2.3 d 3.2C
2.4 d 3.4C
Means with different superscripts are significantly different (P«.05).
fully exposed breast muscle might account for this difference. Chilled carcasses did not differ in water or brine uptake based on time of fillet removal; however, uptake of chill media was significantly higher for carcasses chilled in salt solution than for carcasses chilled in water (Table 1). The enhancement of brine uptake for carcasses chilled in salt solution has been documented and discussed by Hoey et al. (1983) and Dukes and Janky (1984). Significant differences in water or brine uptake have been observed only when sampled carcasses were uniform in size. This uniformity allows small mean differences in uptake to be significant because of the relative lack of variation in this parameter under these conditions. Breast muscle pH at time of boning was not affected by the chilling media but was significantly decreased as the interval from slaughter to time of boning was increased (Table 2). These data were consistent with previous findings reported by Stewart et al. (1984a,b) for excised broiler breast muscle sampled at similar time intervals postmortem. Shear values of water-chilled fillets or fillets harvested from water-chilled carcasses significantly decreased as the time interval between slaughter and fillet removal was increased (Table 2). Values observed were similar to those reported by Stewart et al. (1984a) for broiler breast muscle excised at similar time intervals postmortem. When brine was used as the chilling medium, shear values for hot-boned and chill-boned fillets were not significantly different. However, shear values of age-boned fillets were significantly lower than those observed for fillets harvested at earlier times. Within boning times, brine chilling had no significant effect on shear values of fillets harvested from carcasses after either chilling or aging (Table 2) but significantly reduced shear values of hot-boned fillets to the same level as that observed for fillets harvested from chilled carcasses. Shear force values resulting from either brine chilling of hot-boned fillets or delaying fillet harvest until after carcass chilling indicated that the meat would have been judged as "tough" by the consumer. Simpson and Goodwin (1974) reported that chicken meat with a shear value of 8.0 kg force/g sample or higher was judged "tough" by sensory panelists. The variance associated with the shear value mean for age-boned, water-chilled fillets was significantly smaller than the variance asso-
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composite was analyzed, in duplicate, for moisture content (AOAC, 1970), chloride ion content (AOAC, 1970, Volhard method), and sodium concentration (Shirley et al, 1973). The entire experiment was twice repeated, producing a total of three trials. Data other than shear force values were analyzed by analysis of variance and Duncan's multiple range test procedures (Steel and Torrie, 1980) using programs available in the Statistical Analysis System (SAS, 1982). Shear force data means were tested for unequal variances using an F' (folded) statistic (Steel and Torrie, 1980) and significance of differences between means was determined with a " t " test statistic that uses Satterthwaite's approximation for testing means with unequal variances (Satterthwaite, 1946). Shear force and pH data were tested for correlation (SAS, 1982). Because no significant trial X treatment interactions were observed, data from all three trials were pooled.
BRINE CHILLING AND BONING TIME
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TABLE 2. Breast muscle pH at time of boning, shear force of cooked fillets, and the correlation between these parameters for fillets removed from hot carcasses and either water or brine chilled and fillets removed from chilled or aged, water- or brine-chilled carcasses1
Parameter
Chilling medium
Hot boned 6.41a 6.42a
Chill boned
Age boned
6.16 b 6.27 a b
5.79 c 5.83 c
Water Brine
Shear force, kg force/g
Water Brine
10.2a 8.8b
8.0 b 8.5 b
5.4C 4.9 C
Correlation, r
Water Brine
-.24 -.05
.21 .24
-.02 -.27
a—d Means within a parameter, across both chilling media, with different superscripts are significantly different (P«.05). 1 n=48.
dated with the shear value means associated with hot-boned fillets, regardless of chilling solution, and the variance associated with the shear value mean for age-boned, brine-chilled fillets was significantly smaller than that associated with any of the other shear value means (data not shown). Janky et al. (1982) observed that tenderness was improved (lower shear values) by brine soaking broiler carcass halves, but that the degree of tenderization effect was reduced as the initial tenderness level of the treated substrate was decreased. In the present experiment, it appeared that both aging and brine chilling decreased the natural variation in tenderness of the sampled population. This could have important ramifications in instances where a tight restriction on tenderness variation is required, such as the production of breast fillets for individual segments of the fast food industry. A significant tenderization effect of brine chilling on meat from aged carcasses has been documented (Janky etal., 1978, 1983;Hoeye£ al, 1983; Dukes and Janky, 1984, 1985) for a variety of chilling procedures. The only major procedural difference between these studies and the one herein reported was the use of deep-fat frying as the cooking method instead of baking. It was hypothesized that the difference in cooking method accompanied by the tendency of brine chilling to reduce sample variation masked the tenderization effect of brine chill-
ing on already tender, age-boned fillets. The lack of a tenderness effect due to brine chilling for chill-boned fillets might also be due to the above hypothesis. Correlation of shear force with pH at time of boning was not significant within any individual boning time-chill solution combination (Table 2); however, correlations over the entire experiment or within a chill solution were positive and significant (data not shown). This agreed with conclusions drawn by Stewart et al. (1984a) that pH and tenderness of meat are related to physiological changes in the muscle postmortem as a function of time but do not necessarily have a cause and effect relationship. As expected, chloride and sodium concentration in cooked fillets was significantly increased by brine chilling, regardless of boning time (Table 3). The additional sodium content would not pose a large problem, commercially, because most of the fillet-type product is destined for institutional uses such as fast-food outlets. In these situations, the sodium chloride level of the batter and breading mixes could be adjusted so that overall sodium content for these types of products would not be increased. Other chloride salts might also be substituted for sodium chloride in the chilling media (Palladino and Ball, 1979; Hoey et al, 1983; Sams et al, 1986). Hot-boned fillets, brine chilled as fillets, had significantly higher sodium and chloride levels in the cooked meat than
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pH
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SAMSANDJANKY TABLE 3. Chloride, sodium, and moisture contents of cooked fillets removed from hot carcasses and either water or brine chilled andfilletsremoved from chilled or aged, water- or brine-chilled carcasses
Parameter
Chilling medium
Hot boned
Treatment Chill boned .llc .16 b
Age boned
Water Brine
.llc .31 a
.10 c .17 b
Sodium, mg/100 g
Water Brine
85.7 cd 236. l a
93.7= 125.3b
78.1 d 129.5b
Moisture, %
Water Brine
64.0a 64.0a
64.4a 64.5a
64.5 a 64.5 a
Means within a parameter, across both chilling media, with different superscripts are significantly different (P=S.05).
fillets removed from chilled or aged carcasses (Table 3). These data were consistent with differences in brine uptake between fillets and carcasses previously discussed. Sodium levels of cooked meat from water-chilled samples were somewhat higher and more variable than expected; however, chloride levels were consistent with normal values for chicken light meat(USDA, 1979). The chloride ion has been associated with the tenderization effect of brine chilling (Janky et al., 1983; Palladino and Ball, 1979; Hoey et al., 1983). Janky et al. (1983) observed maximum tenderization of brine-chilled broiler breast meat when raw tissue chloride levels were between .75 and 1.0%; however, the minimum or threshold concentration required to produce the tenderization effect has not been determined. In the present experiment, chloride levels of postchill harvested fillets from brinechilled carcasses were very low by comparison with chloride levels of the hot-boned, brinechilled fillets and might have been below the threshold level required to produce a tenderization effect. Percent moisture of cooked meat samples was not affected by boning time or chilling medium (Table 3). Janky et al. (1983) related the tenderization effect of brine chilling to chloride-induced increases in cooked meat moisture or water-holding capacity. In the present study, this type of relationship was not found. The tenderization effect of brine chilling
was evident with hot-boned fillets; however, water content was not different. Brine chilling may also improve tenderness through interference with the normal mechanism of rigor development by precipitating calcium ions released from the sarcoplasmic reticulum as calcium chloride. In conclusion, boning time produced the greatest effect on tenderness of broiler breast meat with tenderness improving as the length of time between slaughter and boning was increased. Brine chilling improved tenderness of hot-boned fillets to the same level as that observed for fillets harvested from carcasses immediately after chilling but had no effect on average shear force of fillets harvested postchill or after aging. Improvement in tenderness of brine-chilled, hot-boned fillets could not be explained on the basis of pH or water holding capacity but was related to higher tissue chloride ion concentration. REFERENCES Association of Official Analytical Chemists, 1970. Official Methods of Analysis. 10th ed. Assoc. Offic. Anal. Chem., Washington, DC. de Fremery, D., and M. F. Pool, 1959. Rate of rigor mortis development in relation to tenderness of chicken muscle. Poultry Sci. 38:1180-1181. Dodge, J. W., and W. J. Stadelman, 1959. Post mortem aging of poultry meat and its effect on the tenderness of breast muscles. Food Technol. 13:81 — 84. Dukes, M. G., and D. M. Janky, 1984. Physical characteristics of pectoralis superficialis from broiler
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Chloride, %
BRINE CHILLING AND BONING TIME
cooked yield and tenderness of cut up broiler parts. Poultry Sci. 52:1103-1111. Palladino, D. K., and H. R. Ball, Jr., 1979. Effects of selected inorganic salts on certain tenderness characteristics of spent hen muscle. J. Food Sci. 44:322-326. Pool, M. F., D. de Fremery, A. A. Campbell, and A. A. Klose, 1959. Poultry tenderness. II. Influences of processing on tenderness of chickens. Food Technol. 13:25-29. Sams, A. R., M. G. Dukes, and D. M. Janky, 1986. Tenderness and sensory evaluation of pectoralis superficialis from broilers chilled in potassium chloride, sodium chloride, or Neobakasal® salt substitute. Poultry Sci. 6 5 : 7 3 8 - 7 4 1 . SAS Institute, Inc., 1982. SAS User's Guide: Statistics. SAS Inst., Cary, NC. Satterthwaite, F. W., 1946. An approximate distribution of estimates of variance components. Biometrics Bull. 2:110-114. Shirley, R. L., J. F. Easley, J. P. Feaster, C. B. Ammerman, and J. E. Moore, 1973. Atomic Absorption Spectrophotometry. In Equipment and Procedures, 4th ed. University of Florida, Gainesville, FL. Simpson, M. D., and T. L. Goodwin, 1974. Comparison between shear values and taste panel scores for predicting tenderness of broilers. Poultry Sci. 53:2042-2046. Steel, R.G.D., and J. H. Torrie, 1980. Principles and Procedures of Statistics, 2nd ed., McGraw-Hill Book Co., New York, NY. Stewart, M. K., D. L. Fletcher, D. Hamm, and J. E. Thomson, 1984a. The influence of hot boning broiler breast muscle on pH decline and toughening. Poultry Sci. 63:1935-1939. Stewart, M. K., D. L. Fletcher, D. Hamm, and J. E. Thomson, 1984b. The effect of hot boning broiler breast meat muscle on postmortem pH decline. Poultry Sci. 63:2181-2186. United States Department of Agriculture, 1979. Composition of Foods: Poultry Products, RawProcessed-Prepared. Agric. Handbook No. 8-5. USDA Sci. Educ. Admin., Washington, DC.
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