| The demand of beef is increasing with the increase in living standards of Chinese people. It is one of the main fresh meat products in the international market. There is a high demand of good quality beef. Therefore, the study of modified atmospheric packaging (MAP) in the preservation of fresh beef is of practical value and great significance. Unlike other domestic researches involving the technology of MAP, most of which mainly discuss on its appliance in fresh pork or other related products, this study is focused on methods and conditions to preserve fresh beef at low temperature in modified atmosphere with the aim of extending the shelf life. It was studied to apply MAP combined with vacuum and/or preserving agents pretreatment, storage at low temperature in the extension of the shelf life of fresh beef. The parameters about the effect of preservation include color difference value, pH value, total microorganism count, cooking loss, H2S experiment and organoleptic evaluation. The overall evaluation of the effect of preservation was obtained after single factor test was compared.First, application of MAP to preserve fresh beef was studied in this paper. At present MAP was an advanced technology to preserve fresh meat. The atmosphere contained O2, CO2 and N2. The O2 and CO2 had preservative effect and the N2 is only served as a kind of containing atmosphere. The suitable storage temperature of 0—4℃ was obtained based on the experiment of storing the fresh beef at different temperature (ambient temperature, 4℃ and 0℃) in the same atmosphere. To optimize the gas concentrations, this paper studied the effect of different proportion of atmosphere on the preserve of fresh beef. Thus, the oxygen concentration, that is 40％ and the carbon dioxide concentration, that is, 25％ were selected to be most appropriate to preserve fresh meat for 7 days at 0—4℃. Second, the methods of MAP combined with lactic acid, potassium sorbate and ascorbic acid as preserving agents to preserve fresh beef was studied. The result showed it was effective to extend the storage of fresh beef. The test about the additional dosage and proportion of the various preserving agents mentioned above showed the decontaminating of fresh beef with 0.1g/dL lactic acid, 2.0g/dL potassium sorbate, 3.0g/dL ascorbic acid for ten minutes simultaneously prior to packaging in modified atmosphere could significantly reduce total microorganism count of fresh beef and preserved the fresh beef for 10 days. In this study, a better preservative effect was obtained with vacuum pretreatment prior to packaging fresh beef in modified atmosphere. The test showed all of these factors, such as the proportion of atmosphere, final temperature and pressure of vacuum pretreatment, had an impact on the preservative effect. By optimization experiment, the pretreatment with 4℃ as the final temperature and 1200Pa as the pressure of vacuum pretreatment prior to packaging in 40％O2,25％CO2,35% N2 atmosphere had the best effect on preserving fresh beef with a result of 14 days storage at 0—4℃ and the fresh beef still remained the sensory quality as first grade fresh meat. Further research is needed to provide a technology for the storage of fresh beef according to these results. |
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