| Controlled freezing point technology was a beneficial method for storing fresh food, which could maintain normal metabolism, inhibit the growth of microorganisms and prolong the refreshment. To our knowledge, although controlled freezing point technology was widely applied to fruits and vegetables, and its application in meat increased gradually. The study combined controlled freezing point technology with high-pressure treatment or modified atmosphere packaging, and investigated the qualities of beef and mutton under different conditions. At last, electronic nose technology was used for prediction of the storage shelf life of beef and mutton, in order to provide a reference for the application of controlled freezing point technology in preservation of fresh beef and mutton. The research content and major results of experiment were clarified as follows:1.In this study, Simmental beef was used as the material to investigate the effect of high pressure at 150 MPa on the quality of beef stored at ice temperature(-2℃), giving a reference to develop a new method of beef storage. The results showed that comparing with the control group, the sensory scores of the beef treated by 150 MPa at 20℃ for 15 mins were higher. Compared with control group, the change of indexes such as texture, cooking loss rate, p H of beef treated by high pressure was slower. The storage time of 150 MPa beef was 32 days, extending 7 days than control group. It is reasonable to conclude that high pressure is beneficial for prolonging the storage period of the beef at ice temperature.2.In order to extend the storage time of fresh mutton, effect of modified atmosphere packaging(MAP) with various gas components on the quality of fresh mutton during ice temperature storage were determined. Sensory evaluation scores, color, drip loss rate, TVB-N, p H value and microbial loads of the mutton samples packed under 75%O2+25%CO2 and 75%N2+25%CO2 atmosphere stored at ice temperature(-1℃) were analyzed, vacuum packaging as control. The results showed that the drip loss rate of fresh mutton in vacuum package is significantly higher than that of modified atmosphere packaged mutton, but the color and sensory evaluation of mutton packed under 75%N2+25%CO2 atmosphere were worst among the three types of pakages. Mutton packed under 75%O2+25%CO2 atmosphere had the best color and sensory evaluation scores, less drip loss rate, and the lower p H value. After 42 d storage of the mutton packed under 75%O2+25%CO2 atmosphere at ice temperature(-1℃), the total amount of bacteria, Pseudomonas, lactic acid bacteria were 5.91(lg(CFU/g)), 5.95(lg(CFU/g)) and 5.23(lg(CFU/g)) respectively, and the total amount of bacteria was not higher than that of level two fresh meat according to National Standard. In general, 75%O2+25%CO2 atmosphere package combined with ice temperature(-1℃) can extend storage time of fresh mutton as long as 42 days, and this method is suitable for keeping quality of fresh mutton during storage.3.The electronic nose was applied in predicting the freshness of beef and mutton stored at ice temperature. Electronic nose could distinguish from the meat stored at different storage times under ice temperature in various treatments(the beef treated by 150 MPa vs. the control group and the mutton packed under 75%O2 + 25%CO2 vs. 75%N2 + 25%CO2 atmosphere). Besides, with electronic nose, we built up the model based on parameters of sensory evaluation, p H and cooking loss rate and the model based on parameters of sensory evaluation, TVB-N and total plate count, used for forecasting other indicators not involved in models. The regression analysis of the predicted values and measured values showed outstanding prediction in diverse quality indexes of beef and mutton under each storage conditions. The establishment of electronic nose model provided a convenient and accurate evaluation for testing the quality of beef and mutton stored at ice temperature in different groups and made extraordinary meaning of preserving beef and mutton. |
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