Protective effects of enzymatic hydrolysis products of pomelo peel cellulose on Lactobacillus plantarum during freeze-drying process

The successful application of probiotics in food industry depends on the use of good cryoprotectants. This paper was aimed to evaluate protective effects of enzymatic hydrolysis products of different degrees of pomelo peel cellulose (EHPC) on Lactobacillus plantarum during freeze-drying process. The data showed that in contrast to trehalose, the survival rate of L. plantarum was increased obviously under the optimal composite cryoprotectants, which consisted of trehalose and EHPC for 2 h with the mass ratio of 8:2. In addition, the morphology, water-related indices, glass transition temperature (Tg) and cell membrane integrity of lyophilized L. plantarum powder were also evaluated. The results showed that the water content of L. plantarum prepared by the optimal composite cryoprotectants was lower, which was in a reasonable range and conducive to subsequent storage; the Tg and cell membrane integrity were significantly improved. Furthermore, the macromolecular fibers of composite cryoprotectants provided a good habitat and attachment space for L. plantarum, and the sheet fibers with large area acted as a physical barrier to prevent the damage to cells from adverse external environment. The composite cryoprotectants from this study could be considered for industrial development of probiotics.