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Protection mechanism of alginate microcapsules with different mechanical strength for Lactobacillus plantarum ST-III

Zhao, Meng, Qu, Fangning, Wu, Zhengjun, Nishinari, Katsuyoshi, Phillips, Glyn O., Fang, Yapeng
Food hydrocolloids 2017 v.66 pp. 396-402
Lactobacillus plantarum, bile salts, cell membranes, correlation, encapsulation, gastric juice, gelling properties, hydrocolloids, lactic acid bacteria, membrane fluidity, particle size, permeability, strength (mechanics), viscosity
Alginate microcapsule is widely used to encapsulate and protect lactic acid bacteria (LAB). This study aims to design microcapsules with different mechanical strength and clarify their protecting mechanism for Lactobacillus plantarum ST-III under simulated digestive conditions through physical and physiological analysis. By controlling viscosity and gelling ability of alginate solution, a series of microcapsules with the same particle size (ca. 400 μm) and varying mechanical strength (5.4–51.9 N) were prepared. Cell survivals in simulated gastric juice (SGJ) and bile salts (BS) were found to be positively correlated with the mechanical strength of microcapsules. Diffusion experiments using different probes showed that the permeability coefficients of the microcapsules decreased with increasing mechanical strength. Moreover, membrane integrity and membrane fluidity of encapsulated LAB in SGJ were reduced to a less extent and tended to maintain at normal physiological values, with increasing mechanical strength. In contrast, cell membrane integrity was much more reduced (<4.0%) and membrane fluidity was markedly augmented in BS, regardless of the mechanical strength of microcapsules, indicating seriously damaged cells with abnormal physiological properties. These physical and physiological indexes together manifested the protection mechanism of alginate microcapsules with different mechanical strength for LAB.