Study On Immobilization Of Lactase And Low-Lactose Milk

In the first place, this thesis researched into the immobilizing methods and the immobilized biological characteristics of lactase, and discussed the feasibility of using these methods in industrial manufacture. Then starting from the practical requirement of industrialization, to improve the hydrolytic ratio of lactose in the milk and ensure the quality of milk, we introduced the cutting-edge biological enzyme technique into the manufacturing techniques of low-lactose milk. The requirements of the new production were that: the types of nutrition were completed for human health, the flavor is pure, fragrant and sweet, the hydrolytic ratio of lactose is above 70%, and also the cost of manufacture is relatively low. The following are the summary of this thesis:(1) Using the gelatin as the carrier to immobilize the lactase, we can get a preferable effect of immobilization. When the concentration of gelatin was 150 g/L, the concentration of glutaraldehyde was 0.5%, the lactase amount was 5 g/L, pH value was 7.2 and mixing round time was 3 minutes, the result of lactase activity recovery ratio was up to 78.12%. And we can confirm that the pH stability, thermal stability and storing stability on the immobilized lactase was improved remarkably.(2) The iodimtry method and enzymic method which are used to determine the hydrolytic ratio were applied on the same sample production. After the statistical processing of the data, we get the result that the standard deviation of these two methods were respectively 0.4370, and 0.4526;the CV value of them were respectively 0.00796, 0.00831. Therefore, we can conclude that the accuracy of iodimtry method was a little bit better than the enzymic method. Apparently their distinct characteristic was that they can reach a satisfactory mensuration result with only ordinary apparatus. So that our suggestion was thatiodimtry and enzymic method were suitable for the general using of enterprise.(3) When researching into the effects of the conditions of enzymic technics on low-lactose milk hydrolytic ratio, after the analysis of orthogonal experiment,we can find that it is comparatively easy to get a hydrolytic ratio up to 70%. Considering the long period of hydrolyzation will increase the costing and decrease the efficiency in the manufacture, and also the pollution in this progress will probably decrease the quality of milk, we chose the No. 12 to do the experiment repetitively, shortened the hydrolytic time to determine the hydrolytic ratio. The result showed that when the hydrolytic temperature was 40℃, the amount of the lactase was 0.8g/kg, function time was 3 hours , pH value was 6.6 and amount of Mg2+ was 0.5 mL, the optimization of the hydrolytic technique can be reached.