PROCESSING PROPERTIES OF BEEF CLOD MUSCLES AS AFFECTED BY ELECTRICAL STIMULATION AND POST-RIGOR FROZEN STORAGE 1

PROCESSING PROPERTIES OF BEEF CLOD MUSCLES AS AFFECTED BY ELECTRICAL STIMULATION AND POST-RIGOR FROZEN STORAGE 1 R. N. Terrell 2, J. A. Jacobs 3, J. W. Savell 2 and G. C. Smith 2 Texas Agricultural Experiment Station, Texas A&M University, College Station 77843 Summary Effects of frozen storage (--18 C or --4 C) for 8 mo on sensory and processing properties of electrically stimulated (ES) beef clods were determined. Eight pairs of clod muscle groups (left side = ES; right side = not stimulated, NES) from Santa Gertrudis bullocks (15 to 18 mo of age) that had been fed a high concentrate grain diet for 13 d, were used. After 4 too, clods stored at -18 C had less (P<.O1) off-flavor, were more (P<.1) palatable and had more (P<.5) salt-soluble protein (SSP) than clods stored at -4 C. These properties were not affected by storage temperature after 6 mo of storage but, at that time, clods stored at -18 C had lower moisture and higher fat contents than those stored at -4 C (P<.5). After 8 mo storage, clods stored at -18 C were more (P<.1) palatable, had less (P<.1)off-odor and had more (P<.1) SSP than those stored at -4 C. Storage temperature rather than ES appeared to cause these differences. Regardless of storage temperature, ES clods had similar SSP and ph values to those of NES clods. (Key Words: Processing Properties, Frozen Storage, Electrical Stimulation, Beef Clods, Salt-Soluble Protein.) Introduction Production of beef for use in manufactured meat products represents a conversion of lowcost sources of energy into edible protein pro- ducts (Beverly, 1979). In this conversion system the biological efficiency of bullocks (3 mo of age or less) is greater than that of steers (Jacobs et al., 1976; Ellis, 1979). Thus, it may be less costly to produce beef from bullocks for processed meat products than to produce Choice grade steers for fresh-chilled retail beef cuts. Since large quantities of beef for manufacturing are frozen and stored for subsequent use in products such as sausage, cffects of frozen storage time and temperature are important factors. Miller et al. (198) studied the processing properties of such beef. They reported that lengthening of the period in frozen storage resulted in greater amounts of thaw exudate and greater losses of extractable protein, both of which are important processing properties. Electrical stimulation of beef has been reported to increase palatability of fresh-chilled cuts, but these effects depend upon individual muscles and other factors (Forrest and Briskey, 1967; Bouton et al., 198; Houlier et al., 198; Savell et al., 1982; McKeith et al., 1981). Because beef from electrically stimulated carcasses may be frozen and stored for subsequent use in sausage products, the combined effects of electrical stimulation and frozen storage on processing properties warrants investigation. Accordingly, the objective of the present study was to determine the joint effect of frozen storage and electrical stimulation on processing and sensory properties of bullock clod muscles intended for use in sausage products. Materials and Methods tt.a. 17 from the Texas Agr. Exp. Sta. This study was partially supported by King Ranch, Inc., Eight paired (left and right) clod muscle Kingsville, TX; LeFiell and Company, Inc., San groups (deltoid, triceps, brachialis and infra- Francisco, CA and Kaybe Foods, Inc., West Chi- spinatus muscles) from Santa Gertrudis bullocks cago, IL. (15 to 18 mo of age) fed a high concentrate UMeats and Muscle Biol. Section, Dept. of Anita. grain diet (13 d) were used. Left sides were Sci. 3Dept. of Anim. Sci., Idaho Agr. Exp. Sta., Univ. electrically stimulated (ES); right sides were of Idaho, Moscow 83843. not stimulated (NES) and served as controls. 964 JOURNAL OF ANIMAL SCIENCE, Vol. 54, No. 5, 1982

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966 TERRELL ET AL. Stimulation was accomplished with a prototype unit 4 (17 impulses at 55 v, 5 amps, 1.8 s impulse with 1.8 s between impulses). Three days postmortem, clod muscle groups were removed, packaged in polyethylene-lined cardboard boxes and assigned to the following treatments: frozen storage of either -18 or -4 C and for a period of, 2, 4, 6 or 8 too. Clods from each treatment group were sampled in serial-section so that the same anatomical location was sampled at each storage period. Starting with the anterior portion ( too) and continuing to the posterior portion (8 too), sections (5.8 cm) were removed with a band saw. These sections were placed, while frozen, into moisture-proof bags and equilibrated (24 h) to a temperature of -2 C before being ground twice through a plate with 4.8-mm holes. Ground samples were analyzed in duplicate for the following: ph (Acton et al., 1972); proximate composition (AOAC, 1975); juice loss during cooking (Wierbicki et al., 1957) and salt soluble protein (SSP, Saffle and Galbreath, 1964). Uniform patties containing.5% NaCI were prepared, cooked in an electric frying pan (19 C for 2.5 min on each side), evaluated for off-odor and then sectioned and served to an experienced eight-member panel. Cooked patties were evaluated according to the following 4Lectro-tenderTM cisco, CA. LeFiell and Co., San Fran- scale: 8 = no off-odor, 1 = extreme off-odor; 8 = no off-flavor, 1 = extreme off-flavor; 8 = extremely moist, 1 = extremely dry and 8 = excellent-would repeat purchase, 1 = poorwould not purchase. Patties were weighed before and after cooking to determine shrinkage. Data were subjected to analysis of variance (Steel and Torrie, 196) and mean separation (Duncan, 1955). Results Results of the analysis of variance for main effects or interactions between treatments and sensory or processing properties of beef clods are presented in table 1. ES did not affect (P>.5) processing and sensory properties of fresh chilled clods ( mo period) and did not affect these properties after frozen storage for 2, 4, 6 or 8 too. However, temperature of storage did affect (P<.1) off-flavor, overall palatability and SSP after 4 mo of frozen storage and off-odor, overall palatability (P<.1) and SSP values (P<.1) after 8 mo of storage. Changes (P<.1) in moisture and fat contents observed after 6 mo of storage probably reflect variation in sampling rather than real differences due to main effects or storage temperature. These data (table 1) suggest that ES does not affect (P>.5) sensory or processing properties of clod muscles frozen and stored at -18 or --4 C for as long as 8 too. However, temperature of frozen storage affected (P<.5) offflavor, off-odor, overall palatability and SSP values at the end of the 4-, 6- and 8-mo storage periods. Since none of the interaction means TABLE 2. MEAN VALUES FOR SENSORY AND CHEMICAL PROPERTIES OF BEEF CLOD MUSCLES, STRATIFIED BY STORAGE PERIOD AND TEMPERATURE Salt-soluble b Storage Storage Overall Off- Off- Moisture, Fat, protein, period, mo temperature, C palatabilitya flavor a odor a % % % 4 --18 6.3 c --4 5.7 d 6 --18 ---4O 8 --18 6.3 c --4 6. d 6.7 c 29.5c 6. d 2.4 d 71.7 c 1.5 c 74.2 d 8.1 d 6.3 c 28.5c 5.9 d 26. d aoverall palatability: 8 -- excellent-would repeat purchase, 1 = poor-would not purchase; Off-flavor: 8 = no off-flavor, 1 = extreme off-flavor; Off-odor: 8 -- no off-odor, I I, extreme off-odor. bsalt-soluble protein as a percentage of total protein. CdMeans in the same column within a storage period with different superscripts differ (P<.5).

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968 TERRELL ET AL. (ES x temperature) within storage period was significant, it is apparent that temperature of storage rather than ES was largely or totally responsible for differences in sensory and processing properties. Mean values for those sensory and processing properties that were significantly affected by temperature within a storage period are shown in table 2. After 4 mo of storage, clods stored at -18 C were more palatable overall, had less off-flavor and had more SSP than those stored at -4 C (P<.5). However, these traits were not affected by temperature at 6 mo of storage. After 8 mo of storage, clods stored at -18 C were more palatable, had less off-odor, and had more SSP than those stored at -4 C (P<.5). These data (table 2) suggest that the lower storage temperature (-4 C) was more detrimental to sensory traits and processing properties than was the higher temperature (-18 C) but these temperature-dependent effects were not consistent across all storage periods. Mean values for sensory and processing properties according to storage period and ES are shown in table 3. None of these differences (ES vs NES) were significant. D/scus$/o~/ Because trimmings from ES cattle are frequently stored as frozen beef for manufacturing, attempts should be made to identify any possible effect of ES (structural damage and(or) biochemical) that may arise from ES and could affect sensory or processing properties. In the present study, ES and temperature of frozen storage did not affect (P>.5) juice loss during cooking. In our two previous studies (Terrell et al., 1981, 1982) we found that ES slightly increased juice loss in clods from animals varying in sex and age, but reduced these values in bullock clods. Ray et al. (198) reported that roasts from ES cold-boned steers had numerically higher yields (less cooking shrinkage) than did roasts for controls (NES), but Swasdee (198) reported that in pork, ES numerically increased juice loss during cooking in three of four muscle groups from picnic shoulders. In the present study, ES did not significantly affect juice loss during cooking or ph. Increasing ph values due to ES do not necessarily result in less juice loss during cooking (i.e., do not result in higher cooked yields). This observation indicates that ES may alter protein structures and thus increase solubility of the proteins in raw clods, but that these structural changes may allow more juice to be released during cooking (i.e., ES may produce conditions similar to those for pale, soft, exudative pork). In the present study, ES did not affect (P>.5) SSP. Terrell et al. (1982) found that ES clods, plates and flanks from fresh chilled beef had numerically more SSP than NES controls. When these cuts were used to make all-beef frankfurters, formulations of 1% ES beef were more moist (P<.5) than formulations made from 1% NES beef. There were no differences in other sensory or processing shrinkage values between ES and NES for frankfurters in that study. However, Swasdee (198) reported that in pork, ES decreased (P<.5) SSP in two muscles from the picnic shoulder and numerically decreased SSP in two other muscles from the same cut. Hildebrand et al. (1977) reported that although clods from aged bulls had more total protein than clods from bullocks, those from bullocks had more SSP. These reports, and data from the present study, suggest that ES of beef, but not of pork, may result in at least a numerical increase in SSP content of raw muscles but, when these muscles are cooked, juice loss may not necessarily be increased. However, data from the present study are insufficient for us to conclude that ES detrimentally affects processing properties of beef. Regardless of ES, temperature of frozen storage had a significant effect on SSP. Clods stored at -18 C had more (P<.5) SSP after 4 or 8 mo of storage than did clods stored at --4 C. Saffle and Galbreath (1964) reported higher SSP values than those in the present study, but they also reported that beef frozen for 24 h at -34 C had 9% less SSP than fresh chilled beef. In our two previous studies (Terrell et al., 1981, 1982) we found a 23% reduction in SSP from chilled as compared to frozen beef clods. The data from the current study suggest that loss of SSP is due to temperature of frozen storage and not ES and that frozen storage of ES beef intended for use in manufactured products may minimize possible ES-induced increases in solubility of protein in such beef. From the results of the present study and others concerning ES, it is apparent that additional studies are needed to determine (1) effects of sex classification and differences

ELECTRICAL STIMULATION AND FROZEN STORAGE OF BEEF MUSCLE 969 between muscles in response to ES in carcasses that are to be used as fresh-chilled beef, and (2) the effects of ES on trimmings to be used freshchilled or placed in frozen storage for subsequent use in processed meat products. Literature Cited Acton, J. C., J. G. Williams and M. G. Johnson. 1972. The effect of fermentation temperature on changes in meat properties and flavor of summer sausage. J. Milk Food Technol. 3 $ :264. AOAC. 1975. Official Methods of Analysis (12th Ed.). Association of Official Analytical Chemists. Washington, DC, pp 417-427, Beverly, J. R. 1979. Genetic and physiological engineering of meat animals. Proc. Meat Ind. Res. Conf., Amer. Meat Inst., Arlington, VA., p 15. Bouton, P. E., F. D. Shaw and P. V. Harris. 198. Electrical stimulation of beef carcasses in Australia. Proc. 26th European Meet. of Meat Research Workers. Natl. Live Stock and Meat Board, Chicago, IL. Abstr. H-6. Duncan, D. B. 1955. Multiple range and multiple F tests. Biometrics 11:1. Ellis, G. T. 1979. Tailoring animal production for market demands. Proc. Meat Ind. Res. Conf., Amer. Meat Inst., Arlington, VA, p 11. Forrest, J. C. and E. J. Briskey. 1967. Response of striated muscle to electrical stimulation. J. Food Sci. 32:483, Hildebrand, C. A., D. R. Basey and J. A. Jacobs. 1977. Effect of maturity on salt soluble protein content of beef muscles, J. Animal Sci. 45 (Suppl. 1) :34,3. Houlier, B., C. Valin, B. Monin and P. Sale. 198. Is electrical stimulation efficiency muscle dependent? Pror 26th European Meet. of Meat Research Workers, Natl. Live Stock and Meat Board, Chicago, IL. Abstr. J-$. Jacobs, J. A., A. D. Howes, J. C. Miller, T. L. Gregory, L. C. Elsberry, D. Basey, A. A. Araji and D. O. Everson. 1976. Production and marketing potential of young bulls fed rations containing different levels of roughages. Pep. for the Idaho Beef Council, Dept. of Anim. Ind., Univ. of Idaho, Moscow. McKeith, F. K., J. W. Savell and G. C. Smith. 1981. Tenderness improvement of the major muscles of the beef carcass by electrical stimulation. J. Food Sci. 46:1774. Miller, A. J., S. A. Ackerman and S. A. Palumbo. 198. Effects of frozen storage on functionality of meat for processing. J. Food Sci. 45:1466. Ray, E. E., D. M. Stiffler and B. W. Berry. 198. Effects of electrical stimulation and hot boning upon physical changes, cooking time and losses and tenderness of beef roasts. Proc. 26th European Meet. of Meat Research Workers. Natl. Live Stock and Meat Board, Chicago, IL., Abstr. H-7. Saffle, R. L. and J. W. Galbreath. 1964. Quantitative determination of salt soluble protein in various types of meat. Food Technol. 18:119. Savell, J. W,, F. K. McKeith, C. E. Murphey, G. C. Smith and Z, L. Carpenter. 1982. Singular and combined effects of electrical stimulation, post mortem ageing and blade tenderization on the palatability attributes of beef from young bulls. Meat Sci. (In press). Steel, R. G. D. and J. H. Turtle. 196. Principles and Procedures of Statistics. McGraw-Hill Book Co., Inc., New York. p 134-137. Swasdee, R. L. 198, Effects of electrical stimulation and post-slaughter chilling on biochemical properties of porcine muscles and factors affecting sausage batter morphology. Ph.D. Dissertation, Texas A&M Univ., College Station. Terrell, R. N., C. G. Ming, J. A. Jacobs, G. C. Smith and Z. L. Carpenter. 1981. Effect of chloride salts, acid phosphate and electrical stimulation on ph and moisture loss from beef clod muscles. J. Anita. Sci. 53:658. Terrell R. N., J. A. Jacobs, J. W, Savell and G. C. Smith 1982. Properties of frankfurters made from electrically stimulated beef. J. Food Sci. 47:344. Wierbicki, E., L. E. Kunkle and F. E. Deatherage. 1957. Changes in the water holding capacity and cationic shifts during the heating and freezing and thawing of meat as revealed by a simple centrifugal method for determining shrinkage. Food Technol. 11:69.