Studies On Quality Formation Of Beef Under Naturally Freeze-drying With Ventilation And The Rule Of Microorganism Alteration

This experiment determines the total water content, water activity and the values This experiment determines the total water content, water activity and the values microbiological index, with hind quarter of bison from the Kubu Qi Desert in Hangjing Qi of Ordos in Inner Mongolia as its raw material, and the local climate from December to February of next year as the processing condition of beef under freeze-drying with ventilation. It finds out the following results:1.In the process of beef under naturally freeze-dying, the total water content and water activity present a gradually declining trend from the first dying weeks to the sixth. The water activity decreases sharply (P<0.05) from the fourth dying weeks to the sixth. It is not obvious to see their changes (P>0.05) in the dying weeks between the first and the third as well as the sixth and the eighth. Finally, the total water content and water activity of the products are, respectively, are12.7%and0.354until the eighth weeks.2. In the overall course of naturally freeze-dried, the acid value, peroxide value and thiobarbituric value of beef show a markedly growing tendency (P<0.05). The final acid value of the products is3.35mg/g. Its peroxide value is1.37mmol/kg and its thiobarbituric value is0.47mg/kg to the drying eighth weeks. The changes of products can not be seen evidently (P>0.05) though the pH value also appears the increasing trend, with5.7as the final pH value.3. The numbers of microorganisms gradually reduce in the procedure of beef under naturally freeze-drying. The sums of aerobic bacterium decline significantly (P<0.05). The totalities of mildew and microzyme fall strikingly during the period from the first drying week to the fifth (P<0.05). The amounts of aerobic bacterium of products are83CFU/g to the eighth weeks, while the levels of mildew and microzyme are7CFU/g. As the workpiece process, the coliform groups lessen little by little, not testing Staphylococcus aureus, Salmonella and Listeria monoctogenes.4. In the drying process, the degrees of water content and water activity much relate to the quantitative of microorganism. The low water content and water activity can suppress the growth of product microorganisms, but they have a bad effect on quality such as flavor and taste etc. At the same time, if water losses much, it will cause the extensive machining period and the severely reducing of product weight, which will have an impact on the economic benefits of meat processing enterprises. The results of this test which measures every indicator reveals that the oxidation and health indicators accords with the relevant standards of nation under the natural conditions of freeze-drying. According to the analysis of varied regularities of each key indicator in the experiment, combining the actual situation of manufacturing enterprises, it takes the beef that has been freeze-dryed for six weeks as the end of the freeze-drying.