Effects Of High Pressure Treatment On Preservative Properties Of Roast Chicken

Roast chicken is a famous traditional meat products in China and loved by consumers because of its special flavor and rich nutrition. But its shelf life was very short because the heating temperature was very low so that the sterilization effects was very bad and it was riched of nutritents, which was suitable for growth of microorganism. Nowadays, the methods of studying storage property of roast chicken were using preservatives or heating, but it could influence nutrients and flavor of roast chicken. High pressure processing is a kind of non-heated sterilization technology, and could improve meat properties and extend shelf life without destroying meat nutrition and flavor. In this thesis, using roast chicken as material, major spoilage microorganisms and changes of microflora during storage, effects of high pressure level, dwell time, gradient oscillatory high pressure treatments and pulsed high presssure treatments on microorganism, physical-chemical properties and sensory quality of roast chicken.1. Major spoilage microorganisms and changes of microflora components of roast chicken during storage of 4℃and 20℃conditions were studied. Results showed that spoilage microorganisms mainly included Bacillus, Lactic acid bacteria, Micrococcus, Brochothrix thermosphacta, Pseudomonas, Aeromonas, Enterobacteriaceae. Storage temperature had no significant effect on microflra component when roast chicken were stored at 4℃or 20℃, Lactic acid bacteria was the main spoilage bacteria during the whole storage, next was Pseudomonas, Enterobacteriaceae prefers higher temperature, but Staphylococcus and Brochothrix thermosphacta decreased.2. Effects of high pressure level(200～600MPa) and dwell time(10～30min) on preservative properties of roast chicken were studied. Results showed that with pressure level higher and dwell time longer, decreased magnitudes of total bacterial count and lactic acid bacterial larger, and during storage the rate of multiplication lower; the pH value and TBA value were increased after high pressure treatmnets and decreased during storage with increased high pressure level and dwell time. There were not significant effects on sensory qualities of roast chicken after high pressure, but during storage, there were significant differentces among treatments because growth rates of microorganisms were different. Comprehensively considered based on whole results, 500MPa and 20min were optimal levels.3. Effects of gradient oscillatory high pressure treatments and pulsed high pressure treatments on preservative properties roast chicken during storage were studied. Results showed that total bacterial counts and lactic acid bacterial counts were significantly decreased after gradient oscillatory high pressure treatments and pulsed high pressure treatments, and during the whole storage, the rate of microorganism multiplication were lower than continious high pressure, so they could enhance sterilization effects and prolong the shelf-life time. But the results were equipvalent between two staged and threee staged gradient oscillatory, it maybe because the first lower high pressure level was lower and dwell time was shorter of three staged gradient oscillatory high pressure treatment; there was not linear relationship between plused times and sterilization affects, the results of one time pulsed high pressure was very bad, they were equipvalent between two times and three times pulsed high pressure treatments.