INFLUENCE OF HOT-PROCESSING AND ELECTRICAL-STIMULATION ON THE BACTERIOLOGY AND RETAIL CASE-LIFE OF VACUUM-PACKAGED LAMB

Carcasses from 48 wether lambs 6 to 9 months of age were utilized to e valuate the effects of hot-processing and electrical stimulation on ba cterial numbers and types of bacteria on lamb cuts, following vacuum p ackaged storage and during simulated retail display. Carcasses were su bdivided into groups of 16. One subgroup was processed conventionally or chilled for 24 h at 1 degrees C. Another subgroup was electrically stimulated (20; 2 s pulses interspersed with 1 s resting intervals; 55 0V, AC, 50-60 cycles/s) at approximately 45 min post mortem and then c hilled conventionally at 1 degrees C until 24 h post mortem. The final subgroup was treated identically to the subgroup receiving electrical stimulation, but was hot-boned immediately following stimulation, vac uum packaged, and chilled at 1 degrees C until 24 h post mortem. At 24 h post mortem the racks from conventional and electrically stimulated carcasses were removed and vacuum packaged. All vacuum packaged racks were then randomly allocated to four post mortem storage intervals (0 , 14, 28 and 42 days) within processing treatments, so that four racks from each processing treatment were evaluated at each storage interva l. Following storage for the designated intervals, racks were fabricat ed into chops. The two centre chops from each rack were placed into st yrofoam trays, over-wrapped with oxygen permeable film and displayed u nder simulated retail conditions for 5 days. Racks were sampled for ba cteriological analyses before and immediately after storage and chops were sampled before and after 5 days of simulated retail display. Four bacterial groups were enumerated (psychrotrophs, pseudomonads, lactic s and Brochothrix thermosphacta). Processing treatments were not found to have any consistent effects upon bacterial populations except for the absence of B. thermosphacta on hot-boned and electrically stimulat ed racks. Neither storage time nor processing treatment produced a sig nificant effect on retail case-life. Consequently, lamb carcasses can be processed using electrical stimulation and hot-boning alone or in c ombination to increase processing efficiency; and cuts can be stored i n vacuum for up to 42 days without reducing the case-life of retail cu ts below an acceptable level of 2 to 3 days. (C) 1997 Published by Els evier Science Ltd on behalf of the Canadian Institute of Food Science and Technology.