In addition to on-going growth in fermented dairy foods, plant-based dairy analogues are also experiencing rapid growth, however, the diversity of plant-based fermented analogues remains low. One reason for this is that while much is known about the compounds that give fermented dairy products their unique flavour, including how they are derived, this knowledge is missing for plant-based dairy analogues. This is because the flavours generated during fermentation are not only a function of the microorganism(s) involved and fermentation conditions but also the composition of the growth substrate. Of interest in this segment is kefir due to its purported health benefits and sensory attributes. In kefir, fermentation is driven by a heterogeneous microbial consortium aggregated in so-called ‘kefir grains’, which consist of different bacterial and yeast genera wrapped in a polysaccharide matrix. Kefir flavour is shaped by a class of secondary microbial metabolites that are volatile and present in trace levels. Due to its ability to measure trace levels of volatile organic compounds (VOCs) in real time Proton Transfer Reaction Time-of-Flight Mass Spectrometry (PTR-ToF-MS) is an ideal tool to measure the generation of these VOCs. In the present work, PTR-ToF-MS was used to determine at what stage of kefir fermentation VOCs were formed and their concentrations in bovine milk and three plant-based milk bases (milk, oat, maize and barley flours). Milks were inoculated with commercial kefir starters, which were diverse microbial consortia. To investigate the integration of additional bacteria into complex microbial communities, a <i>Lactiplantibacillus plantarum</i> strain that allows a bio-enrichment of the riboflavin was also inoculated. The findings improve our understanding of the VOC contributing to kefir flavour and provide information on the influence of fermentation substrate on the generation of VOCs in complex starters that will assist the next generation of plant-based fermented products.

Real-time monitoring of VOCs associated with kefir <i>versus</i> kefir-like (plant-based) fermentation induced inoculating diverse microbial resources

ACS Spring 2022

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Real-time monitoring of VOCs associated with kefir versus kefir-like (plant-based) fermentation induced inoculating diverse microbial resources