Microbiota dynamics and their impact on the metabolites in lupin oat yoghurt analogues

Abstract

The growing demand for nutritious, flavour-rich plant-based yoghurt analogues calls for innovative fermentation strategies. This study examined the impact of three probiotic combinations- Y1 (Lactobacillus delbrueckii subsp. bulgaricus, Streptococcus thermophilus and Lactobacillus rhamnosus), Y2 (Lactobacillus delbrueckii subsp. bulgaricus, Streptococcus thermophilus and Lactobacillus paracasei) and Y3 (Lactobacillus plantarum and Bifidobacterium sps)- on microbial dynamics and metabolite formation in lupin-oat yoghurt analogues, using unfermented milk analogues as a control. Samples were assessed during fermentation and throughout 28 days of refrigerated storage (4 °C) using microbial enumeration, 16S rRNA sequencing, acidification profiling, and mass spectroscopy-based metabolomics. Fermentation increased volatile compounds, from 23 in the control to 28 (Y1), 41 (Y2) and 54 (Y3). Probiotic combination Y3 exhibited the most complex and stable aroma profile, enriched in pleasant volatiles such as butanoic acid, phenylacetaldehyde, and butyl esters which effectively masked off-flavours like hexanal and heptanal. Microbiota analysis revealed stable formulation-specific communities, with- Streptococcus dominating in yoghurt analogues Y1 and Y2, and Bifidobacterium prevailing in yoghurt analogues Y3. KEGG-based functional prediction linked these transformations to microbial enzymatic activities within metabolic pathways. Notably, Bifidobacterium dominance in Y3 facilitated enhanced ester biosynthesis and conversion of aldehydes to acids, highlighting the “bifid shunt” as a key contributor to flavour enhancement. This integrated multi-omics approach highlights the critical role of targeted probiotic selection in modulating fermentation biochemistry, microbial ecology, and sensory attributes in plant-based lupin-oat yoghurt analogues. Notably, Bifidobacterium-driven fermentation in Y3 offers a promising strategy for improving the flavour profile and consumer acceptance of lupin-oat yoghurt analogues.