Study On Microencapsulation Of Lactobacillus Plantarum And The Tolerance In Digestive Tract

Probiotics are live microorganisms which confer a health benefit on the host and the function was preformed by improving host intestinal microbial balance.Probiotic products are prepared based on its characteristics of maintaining intestinal balance and exerting a beneficial effect on the host. Lactobacillus is a commonly used probiotic strain. But low pH gastric acid and bile in digestive tract can do great harm to viable probiotics, thus affect their beneficial effects in intestine.In this study, a combining method of microencapsulation technology with vacuum drying was adopted to entrap probiotics. The sodium alginate and skim milk were used as the wall material, Lactobacillus plantarum and protectants as the core material. Microcapsules were then treated with subsequent vacuum drying aimed at moisture reduction in order to extend the storage time and enable probiotics to survive passage through the gastric tract and arrive alive at their site of action to exert beneficial effects.L. plantarum loaded microcapsules were prepared by extrusion technology, the optimum preparation conditions and protectants ingredient during freeze drying were optimized. In addition, the traditional vacuum freeze drying method was replaced by new two-step vacuum drying method to increase the survival rate of probiotics in frozen microcapsules. The quality of microencapsulation product was assessed based on research in simulated gastrointestinal treatment and storage stability. The main research contents and results were as follows:1,At a low pH and in the presence of pepsin, the main composition and structure of whey proteins were shown to be intact. Consequently, skim milk was used as part of wall material. With the help of response surface methodology, the optimal conditions of preparation of microencapsulation by extrusion technique were as follows:sodium alginate2.68%, calcium chloride0.20mol/L, skim milk4.17%. After being treated in simulated gastric fluid for 3h, the viable cell counts were up to8.79X109CFU/g.2,4types of protectants were selected. The optimum formula was determined through orthogonal experiment:trehalose8%, lactose8%, vitamin C0.2%, and glycerol3%. Under such conditions, the survival rate of dried L. plantarum reached87.2%.3,The improved two-step drying method was the combination of two continuous steps:vacuum thermostatic drying and vacuum freeze drying. The modified method shortened the freeze-drying time and also increased the survival rate of probiotic cells to90.3%.4,After being treated in simulated gastric fluid for3h, the survival rate of viable cells in microcapsules could reach80%. Apparently, microencapsulated L. plantarum showed excellent tolerance to gastric conditions.5,After45min in simulated intestinal fluid, the transparency of microcapsules dropped to the least, and no solid pellets were seen. So microcapsules had been disintegrated, which meets the standard of Pharmacopoeia of the People's Republic of China (Edition2005). Therefore, the microcapsules had excellent disintegration in intestine.6,The survival rates of L. plantarum were nearly70%and60%when the frozen microcapsules were stored at-20℃and2℃for60d. So the optimized microencapsulation method can effectively increase product stability during storage at low temperature.