Extended shelf-life of unrefrigerated prerigor cooked meat

Five experiments were conducted to evaluate the microbial quality of unrefrigerated cooked prerigor beef after the application of oxygen-permeable packaging. Specific objectives were to combine the beneficial effects of aerobic packaging, meat surface acidification and prerigor rapid cooking rates on meat storage stability at ambient temperature. In the experiments, the triceps brachii muscle was dissected from one side 45 min after exanguination of the animal, and samples of 2 × 3 × 5 cm were prepared. Bags made of a strong barrier, plastic film, and a highly oxygen permeable oriented polypropylene, were used. The cooking of the packaged samples covered a number of treatments ranging from cooking in a 70°C water bath to an internal sample temperature of 65°C to cooking in 100°C water for 40 min. Reheating and multiple heat treatments were also included. The pH values of the cooked samples were determined and aerobic plate counts (log(10)/g) were determined for the cooked samples at various intervals during two weeks of storage at 22°C or at 3°C for the control samples. The results indicate that heat treatment alone did not improve shelf stability at 22°C. However, dipping the samples in 80°C solutions of 0·7% citric acid or 1·25% lactic acid for 1 min and draining for 1 min followed by packaging using oxygen permeable bags and cooking in 100°C water for 40 min consistently resulted in shelf stable products at all 22°C storage intervals. The lactic acid treatment was superior to the citric acid treatment because it completely decontaminated the samples and delayed spoilage, especially at 3°C.