Effects of mixed inoculation of Leuconostoc citreum and Lactobacillus plantarum on suansun (Sour bamboo shoot) fermentation

Insight into the autochthonous bacterial strains as starter cultures for improving the flavor profiles of dry-cured duck: Changes in microbial diversity and metabolic profiles

The purpose of this study was to reveal the effect of inoculating autochthonous bacterial strains (Lactobacillus and Staphylococcus simulans) on the flavor profiles, microbial community, and metabolites, and to elucidate the potential mechanism of flavor formation in dry-cured duck. The results indicated that the inoculation of bacterial strains could improve the amount of lactic acid bacteria and Staphylococcus and reduce the counts of Enterobacteria. There was a significant difference in flavor profiles between samples inoculated with different strains. Hexanal-D, acetone, 3-methyl-1-butanol-D, thiophene, hexanal-M, propanal, pentanal, (Z)-2-penten-1-ol and ethanol-D were the potential biomarkers. A total of 70 differential metabolites were screened and identified. Amino acid metabolism and lipid metabolism were the key pathways for the production of flavor and metabolites in dry-cured duck. The results of this study will improve our understanding of the mechanism of flavor formation regarding the inoculation of autochthonous starter cultures.

Screening and characterization of lactic acid bacteria and fermentation of gamma-aminobutyric acid-enriched bamboo shoots

In order to produce fermented bamboo shoots with functional properties, two strains of lactic acid bacteria were selected for inoculation and fermentation. One strain, Lactiplantibacillus plantarum R1, exhibited prominent potential probiotic properties (including gastrointestinal condition tolerance, adhesion ability, antimicrobial ability, and antibiotic resistance), while the other, Levilactobacillus brevis R2, demonstrated the capability of high γ-aminobutyric acid (GABA) production (913.99 ± 14.2 mg/L). The synergistic inoculation of both strains during bamboo shoot fermentation led to a remarkable increase in GABA content (382.31 ± 12.17 mg/kg), surpassing that of naturally fermented bamboo shoots by more than 4.5 times and outperforming mono-inoculated fermentation. Simultaneously, the nitrite content was maintained at a safe level (5.96 ± 1.81 mg/kg). Besides, inoculated fermented bamboo shoots exhibited an increased crude fiber content (16.58 ± 0.04 g/100 g) and reduced fat content (0.39 ± 0.02 g/100 g). Sensory evaluation results indicated a high overall acceptability for the synergistically inoculated fermented bamboo shoots. This study may provide a strategy for the safe and rapid fermentation of bamboo shoots and lay the groundwork for the development of functional vegetable products enriched with GABA.

A Study on the Formation of Flavor Substances by Bacterial Diversity in the Fermentation Process of Canned Bamboo Shoots in Clear Water

Canned bamboo shoots in clear water could produce a unique flavor through bacterial diversity via the fermentation process. Weissella, Streptococcus, Leuconostoc, Acinetobacter, Lactococcus and Lactobacillus were the main microorganisms. Tyrosine was the most abundant free amino acid (FAA), which had a negative correlation with Lactococcus. Ten kinds of flavor substances, such as 3-methyl-1-butanol, acetic acid, 2-phenylethyl ester, benzene acetaldehyde, benzoic acid and ethyl ester, were important influential factors in the flavor of fermented bamboo shoots. Through the verification test of tyrosine and phenylalanine decarboxylase, it was found that Lactococcus lactis TJJ2 could decompose tyrosine and phenylalanine to produce benzaldehyde and benzene acetaldehyde, which provided the fermented bamboo shoots with a grassy aroma.

Dynamics changes in physicochemical properties, volatile metabolites, non-volatile metabolites, and physiological functions of barley juice during Bifidobacterium infantis fermentation

The purpose of this research was to explore the potential of Bifidobacterium infantis fermentation to modify the composition and physiological properties of barley juices. B. infantis JFM12 showed a potent capability to decrease the total sugar contents from 0.39 ± 0.01 mg/mL to 0.35 ± 0.01 mg/mL within 24 h of fermentation. The volatile metabolite profiles were enriched after B. infantis JFM12 fermentation, leading to the changes of 13 aldehydes, 11 ketones, 10 acids, 7 alcohols, and 6 esters. A total of 98 key non-volatile metabolites were identified in the barley juice between before and after B. infantis JFM12 fermentation, including 80 non-volatile metabolites that were remarkably increased and 18 non-volatile metabolites that were remarkably reduced. Furthermore, the antioxidant activities and lipase inhibitory activities of fermented barley juice were higher than those of unfermented barley juice. Overall, B. infantis JFM12 was beneficial in increasing the quality of barley juice.

Co-fermentation of non-Saccharomyces yeasts with Lactiplantibacillus plantarum FST 1.7 for the production of non-alcoholic beer

The non-alcoholic beer (NAB) sector has experienced steady growth in recent years, with breweries continuously seeking new ways to fulfil consumer demands. NAB can be produced by limited fermentation of non-Saccharomyces yeasts; however, beer produced in this manner is often critiqued for its sweet taste and wort-like off-flavours due to high levels of residual sugars and lack of flavour metabolites. The use of Lactobacillus in limited co-fermentation with non-Saccharomyces yeasts is a novel approach to produce NABs with varying flavour and aroma characteristics. In this study, lab-scale fermentations of Lachancea fermentati KBI 12.1 and Cyberlindnera subsufficiens C6.1 with Lactiplantibacillus plantarum FST 1.7 were performed and compared to a brewer's yeast, Saccharomyces cerevisiae WLP001. Fermentations were monitored for pH, TTA, extract reduction, alcohol production, and microbial cell count. The final beers were analysed for sugar and organic acid concentration, free amino nitrogen content (FAN), glycerol, and levels of volatile metabolites. The inability of the non-Saccharomyces yeasts to utilise maltotriose as an energy source resulted in extended fermentation times compared to S. cerevisiae WLP001. Co-fermentation of yeasts with lactic acid bacteria (LAB) resulted in a decreased pH, higher TTA and increased levels of lactic acid in the final beers. The overall acceptability of the NABs produced by co-fermentation was higher than or similar to that of the beers fermented with the yeasts alone, indicating that LAB fermentation did not negatively impact the sensory attributes of the beer. C. subsufficiens C6.1 and L. plantarum FST 1.7 NAB was characterised as fruity tasting with the significantly higher ester concentrations masking the wort-like flavours resulting from limited fermentation. NAB produced with L. fermentati KBI12.1 and L. plantarum FST1.7 had decreased levels of the undesirable volatile compound diacetyl and was described as 'fruity' and 'acidic', with the increased sourness masking the sweet, wort-like characteristics of the NAB. Moreover, this NAB was ranked as the most highly acceptable in the sensory evaluation. In conclusion, the limited co-fermentation of non-Saccharomyces yeasts with LAB is a promising strategy for the production of NAB.