Development and metabolomic characterization of novel functional fermented juices fortified with a probiotic consortium

• Probiotics, such as lactic acid bacteria and yeast, are commonly used for their health benefits. • The fermentation of vegetable substrates with probiotics has the potential to improve the health benefits of foods. • A variety of secondary metabolites were excreted during fermentation, such as aromatic metabolites, phenolic compounds, and hydroxyacids. • New alternatives to dairy-based matrices are emerging, and incorporating new technologies remains a challenge. At present, there is a growing interest in the commercial application of probiotics derived from alternative fermented food products. As a result, this study aimed to explore the performance of a consortium of potential probiotic yeast and lactic acid bacteria ( Pichia kudriavzevii, Lactococcus lactis subsp . hordniae, Lactococcus lactis subsp. lactis (LABs) in producing non-dairy fermented beverages based on the extracts of Annurca apple peels, goji berries, and beetroots obtained with a green procedure of extraction using the Naviglio extractor. We investigated the effects of the consortium fermentation of the extracts on the viability of microorganisms during the process, pH changes and antioxidant activity. The results suggested that all the three extracts were appropriate substrates for the simultaneous growth of two LABs and the yeast strain, and that the total viable count can reach almost 6.5 log CFU mL -1 for LABs. During fermentation acidity increased as a consequence of the metabolic activity of the microorganisms. Consortium fermentation increases also the antioxidant activity of the fermented extracts compared to the unfermented counterparts. We deepened our knowledge by performing metabolomic analysis, to better detect the consistent differences in the metabolites produced during juices fermentation by the consortium. In addition, 149 secondary metabolites were detected by gas chromatography-mass spectrometry (GC–MS), including alcohols, aldehydes, acids, ester, ether, ketones, phenol, and amides differently upregulated or downregulated during fermentation. In summary, these results indicated that our consortium could serve as a potential candidate probiotic for use in fermented matrices such as Annurca apple peels, goji berries, and beetroots, providing a promising strategy for the development of functional foods to prevent chronic diseases.