Analysis Of The Dominant Spoilage Bacteria From Chilling Duck Meat And Research Of The Controlling Technique

Chilling meats refers to fresh carcass always kept in storage temperature of 0 4℃through the full period from processing to retail after slaughtering, instant cooling to 0 4℃of body center temperature within 24 h. They are popular with consumers especially high-income stratum people because of its health, nutrient and good taste. However there is an issue for chilling meats—short shelf time. Corruption of chilling meats are not only related to enzyme activity existed in it but also with the spoilage bacteria. The variety of raw meat species and their source cause the diversity of spoilage bacteria derived from chilling meats. Therefore, it is necessary for us to understand the corruption bacteria and bacterial phase composition in different phase for different meat species which is favorable for choosing effective preservative.In this paper, the traditional isolation culture method was combined with modern bacteria molecular biotechnology methods—16S rDNA to identify dominant spoilage bacteria for further verification of the corruption bacteria in chilling duck. And then the bacterial count change of the dominated spoilage strains was analyzed during storage period as well as the freshness and quality change of meet, including parameters of pH, volatile salt and nitrogen (TVBN), total count, and sensory evaluation. Finally the bacteriostasis of four chosen preservatives of chitosan, lactic acid sodium, cloves and cinnamon are discussed. The optimum formulation of four preservatives are determined by orthogonal experiment. The main research results are as follows:(1) By means of the traditional isolation culture method as well as physiological and biochemical method, pseudomonas, lactic acid bacteria, brochothrix thermosphacta, staphylococcus, aeromonas, enterobacteriaceae and acinetobacter were preliminarily identified.(2) The results of 16S rDNA flora analysis of spoiled chilling duck meet showed that community structure consist of Pseudomonas, Aeromonas, Lactobacillus, Serratia, Arthrobacter, Janthinobacterium and an unidentified bacterial colony. Pseudomonas account for 54% of the amount of identified population ,then Aeromonas, Lactobacillus, Serratia, Arthrobacter, Janthinobacterium and an unidentified bacterial colony take up 15%, 4%,15%,4%,4%,4% respectively.(3) In process of cold storage,. psychrophilic bacteria increase greatly. Till the ninth day, psychrophilic bacteria count had top the total count, and so did Pseudomonas and lactic acid bacteria. So they are also important indicators of hygiene. When compared to the other corruption bacteria, growth rate of Aeromonas is the highest of all. While E. coli, staphylococcus and brochothrix thermosphacta grow more slow. So Aeromonas has an important influence on the corruption of chilling duck meat in later stage.(4) During storage, PH value had been experiencing the trend of high-low-high, which is accord with most literature'report .TVBN value in the 11th days reach a peak, close to the state provisions of spoilage value. The shelf time of chilling duck remained in 4 degrees Celsius under baggie packing is around 11 days, best edible time in 3rd– 5th days.(5)By comparative experiment, comparative analysis of bacteriostatic effect of chitosan, sodium lactate, clove leaching liquid and cinnamon leaching liquid on the main dominant corruption bacteria were conducted. The results showed that as the increase of preservative liquid concentration, the antibacterial ability also follow to strengthen. The preservative liquid of chitosan possessed a notable bacteriostatic effect on the main corruption microbes. Cinnamon leaching liquid owned relatively weaker inhibition function to most bacterial population.(6)Through orthogonal experiment, the significance of influence factors of TVBN value and pH value is obtained, which are as follow: chitosan (A)> clove (C)>cassia fresh liquid (D) > sodium lactate (B) .The optimal formulation is A₂B₃C₃D₂, that is chitosan liquid at concentration of 0.6%(m/v), sodium lactate liquid at 4.5%(m/v), clove liquid at 6%(m/v), cassia liquid at 3.6%(m/v). And through verifying test, the preservative liquid prepared using optimum formulation can easily control the growth of bacteria, is feasible and effective.