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Impact of carcass chill time on the microbiology of horse meat Open Access


Other title
Horse meat
Type of item
Degree grantor
University of Alberta
Author or creator
Walker, Brian D
Supervisor and department
McMullen, Lynn M
Examining committee member and department
Bruce, Heather L (AFNS)
McMullen, Lynn M (AFNS)
Wismer, Wendy (AFNS)
Department of Agricultural, Food, and Nutritional Science
Date accepted
Graduation date
2017-11:Fall 2017
Master of Science
Degree level
Globally, Canada is the third largest producer of horse meat, having an annual production of approximately 700,000 tonnes. Canadian regulatory standards require carcasses harvested for meat to have the warmest part of the carcass cooled to 7°C before meat can be harvested. Other processes can be approved if scientific evidence of the safety of the meat is provided. This research evaluated the microbiological condition of horse meat harvested at an internal temperature of 13°C. Temperature profiles of horse carcasses were created to determine the chill times required to reach internal temperatures of 13°C, 8°C and <7°C, with 17, 26, and 30 h, respectively, to be optimal chill times for operational purposes in the facility. The process hygiene of the abattoir was comparable to what is found in federally regulated beef plants with counts of 3.25 log CFU/1000 cm2 total aerobic bacteria and 0.54 log CFU/1000 cm2 Enterobacteriaceae. Semimembranosus muscles harvested from horse carcasses after 17 (13°C), 26 (8°C) or 30 h (<7°C) of chilling at 2°C had no significant difference in bacteria counts among chill times with approximately 4.5 log CFU/1000 cm2 of total aerobic bacteria, 2.2 log CFU/1000 cm2 of lactic acid bacteria, and Enterobacteriaceae were below the detection limit. Chill time had no effect on the total aerobic bacteria or lactic acid bacteria during the first 60 d of storage; however, after 90 d of storage, steaks from semimembranosus muscles harvested after 17 h of chilling had lower bacteria counts than those harvested at 30 h. Enterobacteriaceae counts on steaks were below the detection limit on most steaks. Metagenomic analysis of the microbial DNA from steaks stored for 90 d revealed an abundance of Pseudomonas and Serratia. Analysis of culturable bacteria from plate count agar similarly determined that Pseudomonas and Serratia were present in high abundance, whereas the culturable microbiota obtained from the all-purpose tween agar had a high abundance of Enterobacteriaceae. All data support the hypothesis that horse meat can be harvested at 13°C with no negative microbiological hygiene or safety issues when compared to horse meat harvested at <7°C.
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