Omics in traditional vegetable fermented foods and beverages

Characterization and comparison of metaproteomes in traditional and commercial dajiang, a fermented soybean paste in northeast China

Dajiang is a popular Chinese fermented soybean condiment. Here, a comparative metaproteomic analysis of traditional and commercial dajiang was performed during fermentation. A total of 4250 and 1421 peptide sequences were obtained from 3493 and 1987 proteins in traditional and commercial dajiang, respectively. 4299 differentially expressed microbial proteins show a high metabolic heterogeneity between the two types of dajiang. The KEGG annotation indicated that there were some pathways related to human diseases, which suggest that some microbes in traditional dajiang fermentation may have greater food safety hazards. In combination with qualitative metabolomic analysis, we further traced metabolic intermediates and key enzymes in several main fermentation pathways of dajiang to be mainly affiliated with Penicillium, Tetracoccus and Bacillus in traditional samples, as well as Aspergilus in commercial samples. These results could provide information for the selection of strains that are more suitable to produce high quality dajiang and other fermented products.

Shift of Aromatic Profile in Probiotic Hemp Drink Formulations: A Metabolomic Approach

Vegetal drinks as a substitute for milk consumption are raising striking interest in the food industry. Soy and rice drinks are the most successful milk substitutes but are low in protein and fiber contents, are rich in sugars, and their cultivation systems are unsustainable; thus, alternative vegetal sources to resolve these limits must be found. A winning candidate could be hemp seed, which is a powerhouse of nutrients, is sugarless, rich in fiber and proteins, and little land and nutrients demanding. The aim is to develop novel drinks obtained from hemp seeds mixed or not with soy and rice and fermented with probiotics (Lactobacillus fermentum, Lb. plantarum, and Bifidobacterium bifidum). The drinks were characterized for their microbial growth, by means of culture-dependent and -independent techniques, and for their volatilome, by means of solid-phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS) analysis. The results showed that hemp seed drinks have a specific aroma and its compounds are dependent on the type of formulation and to the probiotic used. For example, in hemp seed drinks, 2-heptanol, 2-methyl, 2,4-decadienal, 2-butanone, 3-hydroxy, 2,3-butanedione, and propanoic acid were fine descriptors of probiotics fermentations. Multivariate analysis of volatile metabolites and their correlation to some physiological parameters and nutritional values offered a novel approach to assess the quality of functional hemp drinks which could result in a decisional tool for industrial applications.