The effects of MRS, whey protein and blueberry alone, and mixed fermentation on the survival rate of lactic acid bacteria under various freeze-drying conditions were investigated. The surface structure of the freeze-dried powders was also investigated to explore the anti-freezing protection mechanism of mixed whey protein and blueberry fermentation on the bacteria. It was found that the mixed fermentation medium of blueberry and whey protein has a protective effect on the freeze-drying bacteria and is better than the traditional MRS and whey protein medium. The optimal concentration of blueberry juice addition was 9%. The survival rate of the pre-freezing temperature at −80 °C was higher than at −20 °C after the pre-freezing and freeze-drying processes. The freeze-drying thickness of 0.3 cm could improve the survival rate of the bacteria. The Fourier transform infrared spectroscopy results indicated the interaction between the whey protein, anthocyanins, and the surface composition of the lactic acid bacteria.

In this study, lactic acid bacteria (LAB) fermentation and β-galactosidase catalysis methods were combined to increase the lactulose concentration and reduce the galactose and lactose content in a hot-alkaline-based system. The optimal conditions for chemical isomerization were 70 °C for 50 min for lactulose production, in which the concentration of lactulose was 31.3 ± 1.2%. Then, the selection and identification of LAB, which can utilize lactose and cannot affect lactulose content, were determined from 451 strains in the laboratory. It was found that Lactobacillus salivarius TM-2–8 had weak lactulose utilization and more robust lactose utilization. Lactobacillus rhamnosus grx.21 was weak in terms of lactulose utilization and strong in terms of galactose utilization. These two strains fermented the chemical isomerization system of lactulose to reduce the content of lactose and galactose. The results showed that the lactose concentration was 48.96 ± 2.92 g/L and the lactulose concentration was 59.73 ± 1. 8 g/L for fermentation lasting 18 h. The β-galactosidase was used to increase the content of lactulose in the fermented system at this time. The highest concentration of 74.89 ± 1.68 g/L lactulose was obtained at an enzymatic concentration of 3 U/mL and catalyzed at 50 °C for 3 h by β-galactosidase.

Fermentation is an effective method to enhance the bioactivity of plant proteins, yet the link between the functionality and conformational state of fermented soybean 11S protein (F11S) requires clarification. This study first evaluated the antioxidative efficacy of F11S and its application in emulsion systems, followed by a mechanistic investigation into its structural evolution. Results showed that the bioactivity of F11S was strictly fermentation-time-dependent, reaching its peak at 16 h. At this stage, F11S exhibited maximal scavenging capacities for ·OH (84.51 ± 2.53%) and DPPH radicals (93.84 ± 2.62%). Crucially, in a Tween 20 emulsion system, the F11S-16h fraction demonstrated superior oxidative stability, maintaining the lowest peroxide value (4.33 ± 0.53 mmol/kg) after 15 days of storage. To elucidate the mechanism behind this enhanced functionality, structural analysis was conducted. It revealed that while surface hydrophobicity peaked at 12 h due to protein unfolding, extended fermentation to 16 h induced a refolding process, guiding the protein into a thermodynamically stable conformation. These findings indicate that the stable refolded structure formed at 16 h, rather than maximal hydrophobicity, is the key determinant for the superior antioxidant performance and emulsion stabilizing ability of F11S.