Influence of heat shrink treatments on the onset of clostridial "blown pack" spoilage of vacuum packed chilled meat

Storage trials were conducted to determine if short duration high temperatu re treatments applied in commercial heat shrinking of vacuum barrier packs affect the onset of clostridial blown pack spoilage. Spore suspensions of s ix significant gas producers were used: Clostridium estertheticum NCIMB 125 11, and five local psychrotolerant clostridial isolates. Beef striploins, p H 5.5 and 6.0, were cut into steaks and placed into vacuum pouches. Duplica te pouches were inoculated with each test spore suspension for each meat pH /heat treatment/storage temperature combination. After vacuum packaging and heat shrinking, packs were stored at -1.5. 1 or 4 degreesC. Based on time to first-phase gas production (small bubbles in drip), the test strains wer e considered statistically as representing two groups. With both groups, po st-packaging heat treatment had a significant effect on time to gas product ion. Mean times, pooled for the three storage temperatures. to gas producti on with Group A were 49, 39, 36 and 35 days for the no heat, 70, 80 and 90 degreesC treatments, respectively. With Group B these times were 77, 43, 39 and 36 days, respectively. Post-packaging heat shrink treatments of vacuum packaged meat accelerate the onset of Clostridium spp. mediated blown pack spoilage during chilled storage. Possible mechanisms for accelerated onset of blown pack spoilage following heat shrinking of vacuum packs are discus sed. (C) 2001 Elsevier Science Ltd. All rights reserved.