| The paper is consisted of four parts. In part â… , the effects of different packaging materials under vacuum condition on chilled beef storage life were studied. Part â…¡ focused on the application of modified atmosphere packaging(MAP)in chilled beef .The relative characteristics of natural preservatives in preservation of chilled beef were discussed in the part â…¢.In part â…£,research on effects of natural preservatives on shelf life of chilled beef.Part â… :Vacuum packaging(VP) is one of the most important methods extending shelf life of chilled beef. The different packaging materials(PA/CPP , PET/CPP, PET/PA/CPP, PET/AL/CPP, PET/AL/PA/CPP) have different effects on microbial growth, pH value, TVB-N value, TBARS value, percentage of metMb and sensory quality. The result showed that VP could extend shelf life 8-10 days longer than that packaging in the oxygen-permeable foil-wrapped trays. There showed positive correlation between TVB-N value, percentage of metMb, and oxygen transmission rate(OTR) ( p < 0. 05 ) , and no significant correlation between weight loss, pH value, TBARS and OTR ( p>0. 05 ) .Part â…¡:MAP (20%O2/60%CO2/20%N2; 400/oO2/40%CO2/20%N2; 60%O2 /20%CO2/20%N2; 80%O2 /20%CO2/0%N2) could significantly extend the storage life of chilled beef. The higher ratio of O2 in MAP, the more fresh red color the chilled beef had. However, the higher ratio of O2 would result in multiplication of aecrobic bacteria and cut down the shelf life and worsen the quality of chilled beef. The 20 percentage of CO2 in MAP was enough to retard the growth of aerobic bacteria, and with the increase of the ratio of CO2 , there was little significant increase in the ability of inhibition when the ratio of CO2 are more than 20 percentage. The results showed that the 60%O2 /20%CO2/20% N2 had the best preservative effect on chilled beef, in term of microbial, physical and chemical measurements, and sensory attributes, and the treatment could extended shelf life of chilled beef up to 12 days in low temperature(2 1 ) after aging for 8 days at 4 under VP.Part â…¢: Given that the inhibition of bacterial growth and lipid oxidation in chilled beef is critical to retard quality deterioration, the inhibitive effects of tea Polyphenols(TP), chitosan(Ch),potassium sorbate on dominant spoilage bacteria of chilled beef and the antioxidative effects of tea polyphenols,L-ascorbic acid(Vc),BHT on lipid oxidaton were studied in this part. The results showed that tea polyphenols exhibited more effective antioxidation than BHT and L-ascorbic acid(p<0.05) did at level of 0.2g/kg meat.Chitosan and Tea polyphenols showed marked ininhibiton of microbial dominanted in chilled beef and it is very feasible to use the two preservatives combined.Part â…£:Addition of TP,TP+Vc.TP+Ch could extend the storage life of chilled beef markedly ( p < 0. 05 ), and the treatment of TP+Ch was the best one which could keep APC at very low level (2.18 logcfu-g-1),while other treatments were all up to or over the safe warning line (6.0 logcfu-g-1) under vacuum packaging. Packaged in oxygen permeable foil-wrapped trays, with preservatives above had 3-9 days longer storage life than the control.Different preservative methods produced varieties not only in the quality of chilled beef, but also in economic cost. The increasing order of different preservatives methods according to cost was as follows : preservatives combined with trays |
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