Enhanced Quality in Bean Products Through Mixed Fermentation: A Comparative Analysis of Physicochemical, Structural, and Functional Properties of Soybean Products

Abstract

This study investigated the quality evolution of soybean products (soymilk, tofu, dried bean curd) through mixed-strain fermentation with Lacticaseibacillus rhamnosus CICC 6151 and Saccharomyces cerevisiae AS2.400 under optimized conditions (7% inoculum, pH of 5.2, 85 °C/50 min thermal treatment). Physicochemical, structural, and microbial dynamics were systematically analyzed. Key results demonstrated that probiotic tofu exhibited superior water-holding capacity (82% WHC vs. 65% in traditional variants) and enhanced protein retention (Δ + 2.4% during storage), linked to microbial-mediated structural stabilization. Mixed fermentation induced substrate competition (S. cerevisiae biomass: OD₅₆₀ of 1.2 at 10 h vs. L. rhamnosus OD₆₀₀ of 1.0 at 25 h; ANOVA p < 0.001), driving pH-dependent protein network formation (isoelectric precipitation at pH of 4.8 ± 0.1) and volatile profile divergence (PCA explained 82.2-89.1% of variance). Probiotic variants maintained chromatic stability (ΔE < 15 vs. traditional ΔE > 23) and textural integrity (23% lower deformation under compression), correlated with secondary structure preservation (β-sheet increased by 10% in FTIR analysis). These findings establish synergistic microbial-metabolic regulation as a strategy for developing functional bean products with enhanced nutritional and sensory properties.

Keywords: mixed microbial fermentation; physicochemical properties; soybean products; structural characteristics; textural properties.

Figure 1

(A) Production process of probiotic bean products after mixed culturing of L. rhamnosus 6151 and S. cerevisiae AS2.400. (B) Growth profiles of L. rhamnosus 6151 (OD₆₀₀) and S. cerevisiae AS2.400 (OD₅₆₀) (p < 0.01). PCA analysis of three kinds of soybean products: (C) Soymilk of treatment group and control group. (D) Magnesium chloride tofu and probiotic tofu. (E) Magnesium chloride dried bean curd and probiotic dried bean curd.

Figure 2

(A) The texture changes in probiotic tofu during storage for 48 h. (B) The texture changes of magnesium chloride tofu during storage for 48 h. (C) The change in the water holding capacity of the two kinds of tofu during storage. (D) The texture changes in probiotic dried beans during storage for 48 h. (E) Changes in the texture of probiotic magnesium chloride dried bean curd during storage. (F) The change in the water loss rate of the two kinds of dried bean curd during storage. Note: Different lowercase letters above the bar chart and line chart denote significant differences in the same component across time points (bar chart) or between groups at the same time point (line chart), respectively, and “a” denotes the minimum value of this group (two-way ANOVA with Tukey’s post hoc test; p < 0.05).

Figure 3

(A) Correlation analysis of two groups of tofu samples. (B) The color difference in two groups of tofu samples changed with storage time. (C) Correlation analysis of two groups of dried bean curd samples. (D) The color difference in two groups of dried bean curd samples changed with storage time. Note: P, probiotics; M, magnesium chloride, lightness (L*), red-green axis (a*), yellow-blue axis (b*). * p < 0.05.

Figure 4

(A) Changes in protein content in two kinds of tofu during storage. (B) Changes in protein content in two kinds of dried bean curd during storage. (C) Changes in protein subunits of two kinds of tofu during storage. (D) Changes in protein subunits in two kinds of dried bean curd during storage. Note: Different lowercase letters (a, b) above lines indicate significant differences between groups at the same time point (two-way ANOVA with Tukey’s multiple comparisons test; p < 0.05).

Figure 5

FTIR (A) Probiotic tofu. (B) Magnesium chloride tofu. (C) Comparison of secondary structure of two kinds of tofu samples over time. (D) Probiotic dried bean curd. (E) Magnesium chloride dried bean curd. (F) Comparison of secondary structure of two kinds of dried bean curd samples over time.

Figure 6

The SEM images of different tofu and dried bean curd samples. (A) Magnesium chloride tofu × 300. (B) Probiotic tofu × 650. (C) Magnesium chloride tofu × 550. (D) Probiotic tofu × 700. (E) Magnesium chloride dried bean curd × 370. (F) Probiotic dried bean curd × 650. (G) Magnesium chloride dried bean curd × 500. (H) Probiotic dried bean curd × 750.