Microbial Communities and Physiochemical Properties of Four Distinctive Traditionally Fermented Vegetables from North China and Their Influence on Quality and Safety

The bacterial communities and physicochemical characteristics of four types of extremely distinctive traditionally fermented vegetables (pickled pepper (PP), pickled Brassica napobrassica (PBN), salted flowers of wild chives (SFWC), and pickled cucumber (PC)) were identified and compared from north China. Lactobacillus was the main bacterial genus in PP and PBN samples, with Oceanobacillus only being observed in PBN. The predominant genus in SFWC was Weissella, while in PC they were were Carnimonas and Salinivibrio. At the species level, Companilactobacillus ginsenosidimutans, Fructilactobacillus fructivorans, and Arcobacter marinus were abundant in PP and PBN. Levilactobacillus brevis and Companilactobacillus alimentarius were enriched in PP, and L. acetotolerans, Ligilactobacillus acidipiscis and Pediococcus parvulus were observed in PBN. Weissella cibaria and Kosakonia cowanii were abundant in SFWC. Moreover, tartaric acid was the most physicochemical factor influencing microbial composition, followed by malic acid, titratable acidity (TA), and lactic acid. Furthermore, functional analysis demonstrated that the most genes of the bacterial profiles correlated with carbohydrate metabolism. However, some foodborne pathogens were existed, such as Staphylococcus and Arcobacter marinus. The results of this study provide detailed insight into the relationship between the bacterial communities and physicochemical indices of fermented vegetables, and may improve the quality and safety of traditional Chinese fermented vegetables.

Evaluation of Nitrite, Ethyl Carbamate, and Biogenic Amines in Four Types of Fermented Vegetables

Nitrite, ethyl carbamate, and biogenic amines in fermented vegetables are considered harmful compounds. In this study, the concentration of the nitrite, ethyl carbamate, and biogenic amines in four different varieties of fermented vegetables in China was determined. The results show that the nitrite concentration in the fermented cabbage was the highest, followed by fermented mustard, fermented bamboo, and fermented radish. Additionally, nitrite concentration in two fermented cabbage samples and one fermented mustard sample exceeded the maximum allowed residue limit (20 mg/kg) suggested by China’s National Food Safety Standards. However, only one fermented cabbage sample had a very low level of ethyl carbamate (<10 μg/kg). Otherwise, higher biogenic amines were found in the samples of fermented cabbage, fermented bamboo, and fermented mustard. Additionally, the concentration of biogenic amines in some samples exceeded the recommended limit. On the contrary, biogenic amines in fermented radish samples were relatively low. Therefore, the concentration of nitrite and biogenic amine should be closely monitored and controlled during the vegetable fermentation processes, especially for the fermentation processes of bamboo, cabbage, and mustard.

Influence of Drying Type of Selected Fermented Vegetables Pomace on the Natural Colorants and Concentration of Lactic Acid Bacteria

Nowadays, foods with probiotic bacteria are valuable and desired, because of their influence on human gut and health. Currently, in the era of zero waste, the food industry is interested in managing its waste. Therefore, the aim of the study was to determine the influence of drying process on the physicochemical properties of fermented vegetable pomace. The work included examining the influence of the lactic acid bacteria (Levilactobacillus brevis, Lactiplantibacillus plantarum, Limosilactobacillus fermentum and its mixture in the ratio 1:1:1) used for vegetable fermentation (beetroot, red pepper, carrot), obtaining pomace from fermented vegetables, and then selection of drying technique using the following methods: convection drying (CD) or freeze-drying (FD) on the physical and chemical properties of pomace. In the obtained pomace and its dried form, dry substance, water activity, color, and active substances such as betalains and carotenoids by spectrophotometric method and also bacteria concentration were evaluated. After fermentation of pomace from the same vegetable, a similar concentration of lactic acid bacteria was found as well as dry substances, color and colorants. Results of physico-chemical properties were related to the used vegetable type. After drying of pomace, it could be seen a high decrease in bacteria and colorant concentration (betalains, carotenoids) independently from drying and vegetable type as well as used starter cultures. The smallest change was observed for spontaneously fermented vegetables compared to those in which the starter culture was used.

Influence of Fermented Vegetable Consumption on Gut Microbiome Diversity

Objectives The effects of fermented foods on the gut microbiome are of great interest, yet evidence regarding its potential to increase gut microbial diversity, a measure likely associated with health, is lacking. Therefore, we analyzed the microbial composition (bacteria and yeasts) of commercially available fermented vegetables. Furthermore, we conducted a pilot study to assess the feasibility of studying effects of regular consumption of fermented vegetables on the gut microbiome. Methods Six healthy male volunteers (age: 25.5 ± 2.9yrs, BMI: 24.3 ± 1.2kg/m2) participated in a randomized crossover trial, with two 2-week intervention phases each of which was preceded by a 2-week washout phase. Participants consumed 150g/d of either sauerkraut (intervention 1) or a variety of six different fermented vegetables (intervention 2). We used 16S rRNA sequencing to assess the effects of each dietary regime on the composition, diversity and dynamics of the gut microbiome, as well as the composition and diversity of the fermented vegetable microbiome. Results Lactobacillus was the dominant genus in all fermented vegetables; still, the alpha diversity, richness and evenness of the microbiota differed substantially among the different products. Among our study participants, we observed an increase in alpha diversity (Shannon index) after both, consumption of sauerkraut (pre intervention: 3.31 ± 0.74, post intervention: 3.58 ± 0.68) and the selection of fermented vegetables (pre: 3.60 ± 0.93, post: 3.84 ± 0.81). However, the results did not reach statistical significance, due to the high inter- and intra-individual variability as evaluated by beta diversity of the gut microbial communities. Conclusions A longer-term intervention study with fermented vegetables and/or sauerkraut seems feasible. Consumption of fermented vegetables appears to increase the diversity of the gut microbiome, even after a relatively short period of time. However, further studies with a larger sample size are warranted to verify our observations. Funding Sources Institutional budget.

Culture-independent analysis of the bacterial communities in Chinese fermented vegetables and genomic analysis of lactic acid bacteria

Six different fermented vegetables were collected from Zhejiang Province, China, to explore the associated bacterial communities using a high-throughput sequencing platform. A total of 24 phyla, 274 families and 569 genera were identified from six samples. Firmicutes and Proteobacteria were the main phyla in all of samples. Meanwhile, Brevibacterium was the major genus in Xiaoshan pickled radish. Lactobacillus-related genera and Vibrio were the major genera in fermented potherb mustard and its brine. Enterobacter and Cobetia were the major genera in fermented radish and its brine. Chromohalobacter was the major genus in the tuber mustard. These results indicated there were clear differences between the bacterial genera present in Xiaoshan pickled radish, fermented potherb mustard, fermented radish, and tuber mustard. This demonstrated the possible influences of raw materials and manufacturing processes. Furthermore, a large number of lactic acid bacteria were isolated and identified by culture-dependent and 16S rRNA gene sequence analysis, which accounted for more than 68% of all the isolates. In addition, whole genome analysis of Lactobacillus suantsaii, Lactobacillus sakei subsp. sakei, and Weissella cibaria showed they had large numbers of genes associated with carbohydrate metabolism. This may explain why these three bacterial strains can grow in fermented vegetable environments.