Date of Award
Master of Science
Food Science and Technology
Gordon W. Davis
C. C. Melton, H. O. Jaynes
Part I: Effects of Electrical Stimulation Carcass Characteristics and Palatability Attributes of Beef Produced From Three Feeding Regimens.
Twenty forage finished, 20 limited grain finished (low energy) and 19 grain finished (high energy, ad libitum) steers were slaughtered in a commercial meat packing firm. A randomly selected side from each carcass was electrically stimulated (625 volts, 3-5 amps, 20 impulses of 1 sec duration each) within one hour post-exsanguination. All sides were chilled in a 0 C cooler, ribbed at 18-21 hrs postmortem (PM) and evaluated. Five short loin steaks (2.5cm) were removed after 60, 120, 180 and 240 hr PM aging periods for Warner-Bratzler shear (WBS) force and palatability (240 hr only) determinations. Carcasses from steers finished on forage were rated lower for lean color, lean firmness, lean texture, fat color, sensory flavor and sensory tenderness than grain finished steercarcasses. For comparisons between electrical stimulation (ES) and controls (combined feeding regimens, n = 59), ES improved (P < .01) lean color, firmness, texture scores and reduced heat-ring formation. ES sides from grain finished steers exhibited higher (P < .10) marbling scores (Small 30% vs Slight 90%) than control sides, however, ES did not significantly increase the marbling degree in forage finished or limit grain finished steer carcasses. ES steaks broiled to an internal temperature of 70 C for palatability determinations received higher (P < .05) tenderness ratings (5.1 vs 4.8) and had lower (P < .01) WBS force values at 60hr (3.4 vs 4.1 kg), 120hr (3.1 vs 3.8 kg), 180hr (3.0 vs 3.4kg) and 240 hr (2.8 vs 3.2 kg) PM aging periods. Aged (240hr) steaks from all ES sides were less (P < .05) variable (s.d. .79 vs .63 kg of WBS) in tenderness. These data indicate that ES coupled with 5 days cooler aging results in an equal level of tenderness than carcasses (forage of grain) aged 10 days.
Part II: Effects of Postmortem Aging on Fragmentation Index Values.
A total of 472 loin steaks were removed from short loins (n = 118) from electrically stimulated (ES) and non-electrically stimulated (NES) sides cooler aged for 60, 120, 180 and 240 hrs postmortem. Following each aging period, Warner-Bratzlershear (WBS) and Fragmentation Index (FI) samples were removed. Palatability, proximate analysis and histological samples were removed after the 240 hr aging period. FI of frozen longissimus muscle was recorded at two drying times (0 min and 10 min). No difference (P < .01) in correlation of FI residue to WBS force values for drying periods of 0 or 10 min was observed. Simple correlation coefficients (P < .01) of NES and ES muscle relating FI (0 min) of muscle at 60 hr postmortem to WBS force values were (.50 and .44), (.48 and .39), (38 and .36) and (.39 and .31) for steaks aged 60, 120, 180 and 240 hrs PM, respectively. FI of NES muscle accounted for approximately 23, 42, 38 and 15% of the observed variation in WBS force values not explained by selected carcass traits for steaks aged 60, 120, 180 and 240 hrs PM, respectively. USDA beef quality factors accounted for approximately 7% of the variation in shear force value,while FI (0 min drying time) accounted for an additional 10-37% of the variation in shear force for steaks aged 60-240 hours. By omitting the residue drying step, the FI procedure may be reduced by 10min, thus creating a more time efficient procedure for tenderness evaluation using raw muscle cooler aged for 60 hrs. These data indicate that this procedure has potential for commercial application.
Cole, Alfred Benjamin, "Effects of electrical stimulation on physical, chemical and palatability characteristics of beef produced from three feeding regimens. " Master's Thesis, University of Tennessee, 1980.