Lactobacillus Rhamnosus Encapsulated In Maillard Reaction Products Of Whey Proteins And Isomaltooligosaccharide Microbeads

Probiotics had the functions of adjusting host micro-ecosystem flora, enhancing immunity, reducing serum cholesterol and blood pressure and others in physiology. However, they lost vitality easily during processing and storage and under unfavorable conditions of high acid and salt in vivo. Microcapsules were applied to improving survival rate of probiotics in poor situations as one of methods of protecting bacteria. So far, studies on mixed and coated materials used to encapsulate bacteria were so many, but there were still some deficiencies and shortcomings, which were the critical problems to be solved.In this paper, whey protein and isomaltooligosaccharide were selected as subjects for the Maillard reaction in wet heating conditions. The influence of various factors on the degree of reaction was tested. Gel strength index was used to optimize the reaction parameters. Lactobacillus rhamnosus was encapsulated in whey protein / isomaltooligosaccharide Maillard reaction products(WIMRPs) microspheres prepared by emulsification technique coupled with internal cold gelation process, compared with whey protein and mixture of whey protein and isomaltooligosaccharide. Vitality and released ability of each encapsulation materials under simulated gastrointestinal conditions and the stability of storage were determined to provide theoretical guidance in aspect of Maillard reaction products as the microcapsule material.(1) The effect of temperature, time and the ratio of whey protein and isomaltooligosaccharide on Maillard reaction: the results showed that the degree of reaction reached 10% in the set conditions. By studying the effect of temperature, time and the ratio of materials on cold gel strength of Maillard reaction products, the optimum conditions of Maillard reaction were determined. The results were 4: 1 ratios of whey protein and isomaltooligosaccharide, 90℃,2.5h, and gel strength was the maximum(267.46 g/cm2) under this processing conditions.(2) There was good biocompatibility between microcapsule material obtained by optimized parameters and L.rhamnosus. L.rhamnose was encapsulated in the encapsulation materials through emulsification/internal gelation. The microcapsules radius, optical microscopy morphology and encapsulation yield were determined. The microcapsules radius of whey protein, mixture of whey protein/isomaltooligosaccharide and Maillard reaction products were 118,201,183μm, respectively. Encapsulation yield were 85.13%, 87.63%, 88.88%, respectively. Microcapsules using Maillard reaction products had a suitable radius, smooth appearance and good encapsulation yield.(3) Vitality of bacteria was studied after they were respectively encapsulated in whey protein, mixture of whey protein/isomaltooligosaccharide and Maillard reaction products in simulated gastric juice(p H 2.0) and 3% bile salt solution. The vitalities of bacteria were 6.48,7.27,7.49 Log CFU/g in simulated gastric juice for 90 min. The vitalities of bacteria were 6.03,6.49,7.17 Log CFU/g in bile salt for 90 min. The vitalities of Maillard reaction product microcapsule is higher than other two encapsulation materials 0.35 and 2.5 Log in continuous simulation environment of the gastrointestinal tract for 180 min. Compared with other two encapsulation materials, Maillard reaction products showed a higher level of protection for probiotics, which suggested that this material could improve the ability of probiotics to resist gastric acid and bile salt. Vitality of L.rhamnosus reached the maximum and remained constant when microcapsules using Maillard reaction products were placed in simulated intestinal fluid for 60 min. This encapsulation material had a good ability to release in certain site.(4) Through observing the microstructure of microcapsules, the results showed that microcapsules using Maillard reaction products were smooth, seamless and non-cracking. The vitalities of bacteria encapsulated in mixture of whey protein/isomaltooligosaccharide and Maillard reaction products after spray drying were 3.26,3.15 Log CFU/g, respectively. While the vitalities of bacteria encapsulated in mixture of whey protein-isomaltooligosaccharide and Maillard reaction products after freeze-drying were 1.62,1.51 Log CFU/g, respectively. The vitalities encapsulated in mixture of whey protein/isomaltooligosaccharide and Maillard reaction products were 6.23,6.61 Log CFU/g in freeze-drying and 8.26,7.31 Log CFU/g in spray drying after refrigerated for 30 days. Aw of microcapsules using Maillard reaction products reduced after freeze-drying. Maillard reaction products had better stability of storage as wall material.The results of this study showed that the vitality of L. rhamnosus, which were encapsulated in Maillard reaction products of whey protein and isomaltooligosaccharide, was protected better in simulated gastrointestinal. Microcapsules using Maillard reaction products had a good release in certain site. The vitality of bacteria reached expectations after microcapsules were freeze-dried and refrigerated for 30 days.