Understanding the impact of carcass size, chilling rate, and electrical stimulation on beef quality
Date
2019
Authors
Allahodjibeye Djimsa, Blanchefort, author
Nair, Mahesh N., advisor
Woerner, Dale R., advisor
Engle, Terry E., committee member
Hess, Ann M., committee member
Belk, Keith E., committee member
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Abstract
Increasing carcass sizes and mass make it difficult for packers to appropriately chill beef carcasses, resulting in issues associated with tenderness and color. The wide variability in carcass size and weight and the lack of management practices to address it represent a challenge that the industry must address. To our knowledge, few studies have looked at the combined impact of chilling and electrical stimulation on postmortem biochemistry, tenderness, juiciness and color among the current consist of US beef carcasses, hence justifying this study. The study was conducted in two major parts: The first part focused on the effects of carcass size, chilling rate, and electrical stimulation on temperature and pH decline and postmortem biochemistry. Cattle (N =162, < 30 month) were randomly selected at two beef processing plants in the US. The left or right side of each carcass was electrically stimulated (ES) whereas the matching side was not electrically stimulated (NES). Matched sides were conventionally spray-chilled (CC) or delayed spray-chilled (DC). Deep tissue and surface temperature were continuously monitored during chilling in addition to temperature and pH measurements obtained from the muscles Semimembranosus (SM), Longissimus lumborum (LL), and Psoas major (PM) at an initial time (45 to 60 min), 6 h, 12 h, and final chilling time (18 to 28 h postmortem). A six-member panel evaluated the color of the tenderloin (PM). The L*, a*, and b* values of the PM were measured. A nonlinear regression model was fitted to the continuous deep and surface temperatures. Electrical stimulation improved (P < 0.05) the tenderloin color of light weight carcasses but not (P > 0.05) that of heavy weight carcasses. Temperature decline was faster (P < 0.05) in the SM and LL of heavy weight and delay chilled carcasses while pH decline was slower (P < 0.05). The exponential decay models for deep and surface temperatures showed that the rate of cooling differed (P < 0.05) due to the combination of treatment factors. Heavy weight carcasses had slower rates of chilling (P < 0.05). Variability in carcass size resulted in differences in chilling rate. In the second part of the study, the effects of the treatment factors on beef tenderness were determined. Steaks from the loins (LL) collected from the previous study were randomly assigned to 14, 21, 28, or 35 d aging periods. While sensory evaluation was performed on the 14 d steaks, all the aging groups were used to determine Warner-Braztler shear force (WBSF) and slice shear force (SSF) values. Results showed that sensory panel scores were not affected (P > 0.05) by treatment factors. However, WBSF and SSF were affected (P < 0.05) by carcass size and chilling rate. Aging curves were developed using an exponential decay model to predict aging response and describe the tenderization process for the treatments groups. The models indicated significant differences in the rate and extent of tenderization between different treatment groups.
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Subject
carcass size
electrical stimulation
temperature decline
chilling rate
beef quality
nonlinear modeling