Studies On Preparation And Properties Of Microcapsules Containg Lactobacillus Plantarum Based On External Emulsification Method

The probiotics have been proved to have great benefits on human body, and they have been applied to a range of products. However, due to their low tolerance on harsh environments such as human gastric fluid and bile salts, and the easily losing activities, more attention should be payed to conserve them during probiotics processing and shelf life. Commonly,106cfu/g of probiotics is adequate for probiotics consumption. The coated Lactobacillus plantarum was prepared throught external emulsification combined with vacuum freeze-drying, in optimized the processing conditions. In this paper, the properties of microencapsules and Lactobacillus plantarum survival rates in them were studied. The main contents and results were as follows:(1) The effect of bacteria and sodium alginate solution volume ratio, sodium alginate concentration, emulsifier content, emulsification time, stirring speed, and other factors on the embedding rate were investigated through single factor test. Appropriate level and factors for orthogonal testing were selected to creen out the optimum encapsulating conditions: the bacteria and sodium alginate solution volume ratio was1:6, the sodium alginate concentration was2%, emulsification time was10minutes, and the stirring speed was600rpm. Under such conditions, embedding rate of microcapsules of Lactobacillus plantarum reached57.8%.(2) Based on single factor test, the effects of skimmed milk powder, trehalose, glycerol, and sucrose on the freeze-drying performance were investigated. The best protective agent through the orthogonal test was screened out:8%of skimmed milk powder,4%of trehalose,3%of glycerol,6%of sucrose. Compared with the microcapsules without protective agent, the number of viable cells of Lactobacillus plantarum in the alginate microcapsules which were prepared under this condition were improved nearly three orders of magnitude.(3) After being treated in simulated stomach juice for3h and in simulated bile solution for6h, the survival rate of Lactobacillus plantarum in alginate microcapsules was greater than60%and significantly higher than these of free Lactobacillus plantarum. It was indicated that the tolerance to gastric juice and bile salt solution of Lactobacillus plantarum embedding could be improved by external emulsification method. Treated in simulated intestinal juice for40minutes, transmittance of microcapsules descended the least, and remained unchanged. The results showed that the microcapsules prepared by external emulsification method had better disintegrateion. The survival rate of Lactobacillus plantarum reached67.8%, while that of free Lactobacillus plantarum decreased below10%, which showed that microencapsulation could significantly improve the storage stability of Lactobacillus plantarum.(4) We prepared alginate/chitosan microcapsules containing Lactobacillus plantarum by coating alginate microcapsules with chitosan, and analysed their properties. The results indicated that the addition of chitosan could improve acid-resistance of microcapsules. The molecular weight of chitosan, as well as the concentration and pH of chitosan solution had significant effects on acid-resistance of microcapsules. The optimal conditions for preparing microcapsules are as follows:330kDa of chitosan molecular weight,0.4%of chitosan concentration and solution pH5.0. The effects of chitosan on other properties of microcapsules need further study.