| The cooked meat product with its flavorful, delicious and abundant nutrition is popular by the consumer deeply; but it had a relatively short shelf life due to its low sterilization temperature and higher pH during the later storage, transport and distribution. Therefore, prolonging the shelf life of cooked meat product has become bottleneck problem during development. In this thesis, the effects of spoilage microorganisms on roast chicken quality, isolation and identification of predominant spoilage bacteria and the storage characteristics under different storage condition were systematically investigated, and further research on the compound preservative effects on roast chicken was also studied. we would like to a theory basis and technique for the ensuring of the quality and safety of cooked meat products in the period of processing, storage and distribution. The results indicated:1. The storage characteristics of roast chicken under different temperature were studied. Original physical and chemical parameter and total bacterial counts of roast chicken: pH value 6.27±0.09, TVB-N value 16.84±2.60 mg/100g, TBARS value 0.67±0.12 mg/100g, and total bacteria count of 103-104 cfu/g. With the storage time extending under different storage condition, pH value all decreased, TVB-N value all increased and TBARS value had no significant changes. The shelf life of products stored under different storage condition was investigated by analyzing the growth situation of microorganisms and changes of physical and chemical parameter during storage. The results indicated: the shelf life of roast chicken in vacuum-packed (without secondary sterilization)was 5 day at low temperature (0-4℃),1 day at room temperature (20-25℃), and the shelf life of roast chicken in anti-vacuum package was 5 day at low temperature (0-4℃), when the initial bacterial population was about103cfu/g.2. The initial microflora in roast chicken was analyzed. The result showed that Pseudomonas (47.58%) and Staphylococcus (31.34%) were the predominant spoilage bacteria, Enterobacteriaceae and LAB are minor, in addition, yeast was only 1.61 %.3. The microflora in roast chicken at the end of shelf life was analyzed. The result showed that yeast(50.93%) and Pseudomonas(40.16%) are the predominant spoilage bacteria of roast chicken in anti-vacuum package at low temperature, other bacteria is less(only 8.91%); yeast(49.05%) is the predominant spoilage bacteria of roast chicken vacuum packed at room temperature , LAB (22.78%) and Pseudomonas(17.52%) are minor, other bacteria is less(only 10.65%); yeast(49.05%) and LAB(22.78%)are the predominant spoilage bacteria of roast chicken in vacuum package at low temperature, Staphylococcus(17.23%) is minor , other bacteria is less(only 7.34%).4. The spoilage mechanism was studied. Spoilage microorganisms which were inoculated in chicken meat grew rapidly in the 2 -10 day; Bacteria counts on the inoculated chicken meat reached the limited content of 108cfu/g. No matter in low temperature or hypoxia conditions, the LAB grew more rapidly than the yeast, and the ability of decomposing protein to yeast was stronger than LAB.5. Using orthogonal experiment design,the effect of preservation of three kinds of preservative such asε-polylysine, nisin and clove oil on the roast chicken was studied. The result showed that 0.006%ε- polylysine+0.05% nisin+0.60mg/kg clove oil was the optimum proportion. The shelf-life of roast chicken was extended to 12 day.6. Using response surface methodology (RSM) experiment design, the effect of preservation of three kinds of preservative such as sodium lactate, nisin, potassium sorbate on the roast chicken was studied. The result showed that 0.03%nisin+3.00% sodium lactate+0.05% potassium sorbate was the optimum proportion. Result of valedictory experiment showed that the shelf-life of roast chicken was extended effectively, and the predictive and measured values coincided rather well.
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