Lactobacillus delbrueckii is the key functional microorganism of natural fermented tofu sour water involved in the traditional coagulation of Chinese Huizhou Mao-tofu

Bioturbation effect of artificial inoculation on the flavor metabolites and bacterial communities in the Chinese Mao-tofu fermentation

A comparison between artificially inoculated Mao-tofu (CC) and naturally fermented Mao-tofu (MM) indicated that artificially adding Mucor plasmaticus to Mao-tofu dramatically enhanced the essential amino acid (EAA) content, as well as umami and sweet amino acids. Gas chromatography-tandem mass spectrometry (GC-MS/MS) analysis revealed that phenol (3.226 μg/g), 1-octen-3-ol (5.031 μg/g), ethyl heptanoate (1.646 μg/g), and indole (3.422 μg/g) were the key flavor components in Mao-tofu. Unlike MM, CC displayed a substantial increase in esters and a considerable decrease in foul odor substances, including sulfur-containing compounds and indole. Lactococcus raffinolactis, Enterobacter sp. 638, and Streptococcus parauberis KCTC 11537 represented the key bacterial species altering the amino acids and flavor of Mao-tofu according to PacBio single-molecule real-time (SMRT) sequencing and correlation analysis. This study presents the technical feasibility of artificially inoculating Mao-tofu to regulate the core bacterial communities and control the quality of fermented soybean products.

A glimpse into plant-based fermented products alternative to animal based products: Formulation, processing, health benefits

Fermented foods and beverages are increasingly being included in the diets of people around the world, as they significantly contribute to flavor and interest in nutrition and food consumption. Plant sources, like cereals and pulses, are employed to produce vegan fermented foods that are either commercially available or the subject of ongoing scientific investigation. In addition, the inclination towards nutritionally healthy, natural, and clean-label products amongst consumers has encouraged the development of vegan fermented products alternative to animal-based products for industrial-scale production. However, as the vegan diet is more restrictive than the vegetarian diet, manufacturing food products for vegans presents a significant problem due to the limited availability of many raw materials. So further research is required on this topic. This paper aims to review the formulation, quality, microbial resources, health benefits, and safety of foods that can be categorised as vegan fermented foods and beverages.

Yeast diversity in pit mud and related volatile compounds in fermented grains of chinese strong-flavour liquor

Chinese strong-flavour liquor is produced via a traditional solid-state fermentation strategy facilitated by live microorganisms in pit mud-based cellars. For the present analysis, pit mud samples from different spatial locations within fermentation cellars were collected, and the yeast communities therein were assessed via culture-based and denaturing gradient gel electrophoresis (DGGE) approaches. These analyses revealed significant differences in the composition of yeast communities present in different layers of pit mud. In total, 29 different yeast species were detected, and principal component analyses revealed clear differences in microbial diversity in pit mud samples taken from different cellar locations. Culture-dependent strategies similarly detected 20 different yeast species in these samples. However, while Geotrichum silvicola, Torulaspora delbrueckii, Hanseniaspora uvarum, Saturnispora silvae, Issatchenkia orientalis, Candida mucifera, Kazachstania barnettii, Cyberlindnera jadinii, Hanseniaspora spp., Alternaria tenuissima, Cryptococcus laurentii, Metschnikowia spp., and Rhodotorula dairenensis were detected via a PCR-DGGE approach, they were not detectable in culture-dependent analyses. In contrast, culture-based approaches led to the identification of Schizosaccharomyces pombe and Debaryomyces hansenii in these pit mud samples, whereas they were not detected using DGGE fingerprints profiles. An additional HS-SPME-GC-MS-based analysis of the volatile compounds present in fermented grains samples led to the identification of 66 such compounds, with the highest levels of volatile acids, esters, and alcohols being detected in fermented grains from lower layer samples. A canonical correspondence analysis (CCA) suggested they were significant correlations between pit mud yeast communities and associated volatile compounds in fermented grains.

Natural Environmental Variation Determines Microbial Diversity Patterns in Serofluid Dish, a Traditional Chinese Fermented Vegetable Food

Serofluid dish is a traditional fermented food that contains rich microbial populations. To gain insight into the environmental variables shaping the microbial diversity patterns, serofluid dish samples were collected from different areas, and 16S rRNA sequencing was performed. Analyses revealed both species and community diversity, including phylotype richness, Shannon index and phylogenetic diversity, were mostly influenced by pH. Additionally, such effects were corroborated by the Mantel test of pairwise UniFrac distances and variable selection of multiple linear regression models. Eventually, correlations between dominant lineages and the pH of serofluid dish other than geographical distance explained a large portion of the changes in microbial composition and diversity. Lactobacillus and related genera, Pediococcus and Acetobacter were largely driven by the variability of pH, and higher richness was observed under moderate pH ranges. Collectively, the results demonstrated that a microbial diversity pattern in serofluid dish is predictable by natural environmental variation and can be better understood through pH conditions.

Polyvinylidene Fluoride Membrane with a Polyvinylpyrrolidone Additive for Tofu Industrial Wastewater Treatment in Combination with the Coagulation-Flocculation Process

Wastewater from the tofu industry contains many pollutants that are very harmful to the environment, significantly endangering aquatic life and producing a pungent odor. This study aims to prepare a polyvinylidene fluoride (PVDF) membrane with the additive polyvinylpyrrolidone (PVP), and utilize it to treat tofu wastewater in the ultrafiltration (UF) process. Flat sheet membranes were prepared using PVDF that was dissolved in N,N-dimethylacetamide (DMAc) and then combined with the additive material of PVP at the varying compositions of 14.9/0.1, 14.85/0.15, and 14.8/0.2 g of PVDF/gram of PVP. The addition of PVP was proposed to improve the properties of the membranes. Characterization by scanning electron microscope (SEM), water contact angle, and Fourier transform infrared spectroscopy (FTIR) were performed on the PVDF/PVP membrane flat sheet in order to understand and compare changes in the physical and chemical properties that occurred in the membrane. Prior to the UF process, the tofu wastewater was treated by a coagulation–flocculation process through a jar tester using poly aluminum chloride (PAC) as a coagulant. Based on the membrane characterization, the addition of PVP improved the physical and chemical properties of membranes. The pore size of the membrane becomes larger, which could increase permeability as well as the flux value. The TSS and turbidity of the water produced in the UF process decreased with an increase in feed pressure due to a greater driving force generated to facilitate the penetration of the suspended solids. The UF results showed that the effect of PVP on water flux was greatest for the 14.85/0.15 PVDF/PVP membrane for both pure and wastewater. In addition, the highest percentage of rejection for TSS and turbidity were observed in the 14.9/0.1 PVDF/PVP membrane and rejection for TDS was indicated in the 14.8/0.2 PVDF/PVP membrane. Meanwhile, the resulting pH decreased slightly across all samples as feed pressure increased.

Differences in the physicochemical, digestion and microstructural characteristics of soy protein gel acidified with lactic acid bacteria, glucono-δ-lactone and organic acid

This study evaluated the differences in the physicochemical, digestion and microstructure of soy protein gels acidified with Lactobacillus casei (L. casei), glucono-δ-lactone (GDL) and citric acid. The maximum acidification rate was as follows: citric acid > GDL > L. casei. The gelation points of L. casei-induced gel (LC gel) and GDL-induced gel (GDL gel) occurred at 74 min and 55 min; however, gelation point of citric acid-induced gel (CA gel) was not detected because acidification was too fast. LC gel showed the high gel hardness (20.40 ± 2.23 g) and water holding capacity (84.58 ± 0.59%). At the end of intestinal digestion, the average particle size of the LC gel was the largest, but there was no significant difference between GDL gel and CA gel. The microstructure of the GDL gel was found to be the densest. Acidification rate was the "key step" of acid-induced gels, while both the proteolytic and exopolysaccharide (EPS) production capacity were involved in LC gel.