Study On Technology Of Chilled Beef Preservation

Beef is one of the highest quality meat products in the international market, but its quality characteristics and techniques in preservation are burning questions in the development of our meat industry. Beef was used as experimental material in this research. The effect of gas ratio in MAP, the choice of packing material and MAP cooperated with composite natural preservatives on the quality and shelf life of cooling beef were studied. The volatile flavor compounds of beef in MAP were investigated. Finally, the models of quality indicators were established to predict shelf life of beef.1,The effect of different gas concentration in modified atmosphere packaging on the beef preservation was studied. Fresh beef were stored in modified atmosphere packaging at different levels of the concentration of O₂ and CO₂ within 0¹00% by uniform design method. During storage at 4±1℃, the gas concentration in packaging, total number colonies of beef, pH value, TVB-N values, the loss rate of juice, color were detected and analyzed every two days. The results demonstrated that: the influence of relatively high concentration of oxygen or carbon dioxide on beef preservation was not effective, while the shelf-life of beef in MAP (45%O₂ /30%CO₂ /25%N₂) was longest.2,In this experiment, changes in the quality of beef preserved in different plastic bags filled with modified atmosphere (45%O₂/30%CO₂/25%N₂) were monitored. During storage at 4±1℃, the gas concentration in packaging, total number colonies of beef, TVB-N value, lipid oxidation (TBARS), content of metMb, tenderness and elasticity were analyzed every two days. The results demonstrated that the effectiveness of PE/PP/PET composite film was superior to PA/PP/PET composite film and aluminum foil bag for fresh beef packaging whose shelf life could reach to 16 days. PE/PP composite film was not suitable for beef preservation.3,The effect of modified atmosphere packaging(MAP) with composite natural preservatives on fresh beef was studied.Beef treated with composite preservatives (1% chitosan/0.2% tea polyphenols or 1.5% chitosan/0.1%TP) were stored at 4±1℃under different atmosphere with high oxygen concentration (40% 70%).Vacuum-packed samples were used as comparison.The total number colonies of beef, pH value, total volatile basic nitrogen, the loss rate of juice, tenderness, elasticity and color were analyzed every two days. The results indicated that: 70%O₂/20%CO₂/10%N₂ of the modified atmosphere packaging combined with 1% chitosan/0.2% tea polyphenols of natural preservative was most effective for beef preservation.4,Solid phase micro-extraction (SPME) was used to distill the volatile flavor substances of MAP beef and gas chromatography-mass spectrometry (GC-MS) was used for qualitative and quantitative analysis of volatile flavor substances and detecting of the relative contents based on peak area. The results indicated that: 42 kinds of volatile flavor compounds were identified in fresh beef and 32 in MAP (45%O₂/30%CO₂/25%N₂) beef which stored at 4±1℃for 7 days. The volatile substances which lost during storage affected the flavor of beef. The main volatile compounds included 6-Octanal, Monoethyl carbonotrithioate, 2-Propanol,1-Propoxy , 1,2-Benzenedicarboxylic-acid,bis (2-methylpropyl) ester, Methy lester of 2-oxo-Nonanoicacid,2-Nonenal and 2,4,6,10-Tetramethyl-methyl ester Pentadecanoic acid.5,The growth trend of bacteria, total volatile basic nitrogen,a*,pH of fresh beef stored in modified atmosphere packaging at different levels of the concentration of O₂ and CO₂ was studied in the research, then establishment of the indicator simulation to predict the shelf life of MAP beef. During storage at 4±1℃,the total number colonies of beef, TVB-N values, a*, pH were detected and analyzed every two days,then the quality indicators models were founded by STATISTICA software. The results indicated that the models could effectively imitate the dynamic change of number of bacteria and TVB-N values during different storage packaging. The quality indicators models could provide a powerful tool to evaluate microbiological population and tissue damage during different modified atmosphere packaging and period.