Lupin protein isolates influence the nutrition, rheology, and protein profile of lupin-oat yoghurt analogues through probiotic activity

Substituting animal proteins with plant-based alternatives offers a sustainable approach to reducing the ecological footprint of livestock farming. This study explores the effect of protein composition on lupin-oat yoghurt analogues, utilizing oat water extract enriched with protein isolates from Lupinus angustifolius (ANG, rich in legumin) and Lupinus albus (ALB, rich in vicilin), fermented with probiotics Lactobacillus plantarum and Bifidobacterium (BB12). Rheological, textural and microstructural analyses revealed that addition of protein isolates improved water-holding capacity, firmness, cohesiveness and gel strength. However, ALB, rich in vicilin, exhibited superior gel matrix density and stability, while ANG, rich in legumin, contributed to enhanced emulsion stability. Acidification kinetics showed similar pH trends, but lower titratable acidity in ANG, sample suggests distinct protein interactions driven by its legumin-rich profile compared to the vicilin-rich ALB. Fermentation effectively reduced Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols (FODMAPs) content, particularly galactooligosaccharides, suggesting improved digestibility for individuals with irritable bowel syndrome. Organic acid profiling showed greater phytic acid degradation in ANG, which may be linked to enhanced mineral bioavailability. Fermentation led to greater protein breakdown in Lupinus albus than Lupinus angustifolius, with SDS-PAGE revealing dominant vicilin proteins in Lupinus albus and legumin proteins in Lupinus angustifolius, which influenced their gelation behaviour. Allergen mapping suggested probiotic fermentation as a potential method for reducing allergenic proteins, with notable degradation of Lup an 1 in ANG. These findings highlight the potential of lupin protein isolates to optimize plant-based yoghurt analogues by enhancing texture, nutrition, and reducing allergenic properties.