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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.

Freeze drying has been well applied in the preparation of high-efficiency probiotic powders. However, the process is generally accompanied by probiotic viability deficiency, which is the bottleneck for further application. To improve the viability of Bifidobacterium bifidum BB01 during freeze-drying, we optimized the cryoprotectant of B. bifidum BB01 by response surface methodology (RSM) with a Central Composite Design (CCD). In this study, two values of B. bifidum BB01 with different protectant factors were investigated, including freeze-drying survival rate and the viable counts of per unit weight of freeze-dried powder. The optimized cryoprotectants were obtained as follows: glycine of 5.5%, sodium bicarbonate of 0.8%, xylo-oligosaccharides of 7%, arginine of 4.5% and skim milk of 25%. The survival rate and the viable counts of per unit weight of powder were 90.37 ± 1.9% and (2.78 ± 0.13) × 1011cfu·g−1, respectively, both close to the predicted value (88.58% and 2.71 × 1011 cfu·g−1). Our research demonstrated that RSM was successful in optimizing composite cryoprotectant for freeze-dried powder of B. bifidum which can as well protect the probiotic cells.

A directed vat set (DVS) starter was proposed to improve the drawbacks of liquid starters in fermented production and enhance the survival rates of B. animalis subsp. lactis BZ11, S. thermophilus Q-1, and Lactiplantibacillus plantarum LB12. The protective agent formula was optimized using the response surface method (RSM), with the survival rate as the benchmark. The best combination of cryoprotectants was determined to be BZ11: 10 % skimmed milk powder, 3 % sodium glutamate, and 15 % trehalose; LB12: 10 % skim milk powder, 5 % glutamate sodium, and 10 % trehalose; Q-1: 10 % skimmed milk powder, 3 % sodium glutamate, and 10 % trehalose. The survival rate of BZ11 significantly increased to 92.87 ± 1.25 %. The DVS fermented milk did not differ significantly from the control group regarding cholesterol removal, live cell counts and pH (p > 0.05). All DVS can be stored for at least 2500 d at −20 °C—this DVS starter for fermented milk benefits from its large-scale and automated commercial production. [Display omitted] • DVS can prepare fermented milk with good performance. • Milk prepared by DVS with a good cholesterol degradation rate. • The protective effect of trehalose and sodium glutamate on BZ11 was extremely significant. • BZ11 survival rate as high as 92.87 ± 1.25 %. • Milk fermented with BZ11, LB12, and Q-1 had good physicochemical indexes and flavor. [ABSTRACT FROM AUTHOR]

Freeze drying has been well applied in the preparation of high-efficiency probiotic powders. However, the process is generally accompanied by probiotic viability deficiency, which is the bottleneck for further application. To improve the viability of Bifidobacterium bifidum BB01 during freeze-drying, we optimized the cryoprotectant of B. bifidum BB01 by response surface methodology (RSM) with a Central Composite Design (CCD). In this study, two values of B. bifidum BB01 with different protectant factors were investigated, including freeze-drying survival rate and the viable counts of per unit weight of freeze-dried powder. The optimized cryoprotectants were obtained as follows: glycine of 5.5%, sodium bicarbonate of 0.8%, xylo-oligosaccharides of 7%, arginine of 4.5% and skim milk of 25%. The survival rate and the viable counts of per unit weight of powder were 90.37 ± 1.9% and (2.78 ± 0.13) × 1011cfu·g−1, respectively, both close to the predicted value (88.58% and 2.71 × 1011 cfu·g−1). Our research demonstrated that RSM was successful in optimizing composite cryoprotectant for freeze-dried powder of B. bifidum which can as well protect the probiotic cells. [ABSTRACT FROM AUTHOR]