Physicochemical Properties, Rheological Characteristics, Flavor Profile and Antioxidant Activity of Fermented Plant-Based Alternative to Yoghurt from Avena sativa L. and Prunus dulcis (Mill.) D. A. Webb

This study compared oat yoghurt (OY), almond yoghurt (AY), oat–almond yoghurt (OAY), and an unfermented oat–almond milk (OAM) to clarify how blending and lactic fermentation affect fermented plant-based alternatives to yoghurt. Nutritionally, OAY showed a balanced profile (protein 2.87 g/100 g; fat 5.18 g/100 g), intermediate between AY (3.29 g/100 g, 8.89 g/100 g) and OY (2.39 g/100 g, 3.30 g/100 g). Fermentation enhanced physical stability, as OAY showed higher water-holding capacity (58.08%) and high viscosity (5381.49 mPa·s), together with the highest viable lactic acid bacteria count (7.1 log10 CFU/g). Scanning electron microscopy revealed that co-fermentation formed a denser, more cohesive multiphase gel network with reduced pore size compared with OAM and AY. All samples exhibited shear-thinning behavior; dynamic rheology indicated weak gel features (G′ > G″), and OAY showed the highest G′, implying a reinforced network likely associated with interactions between oat β-glucan and almond proteins during fermentation. Volatile profiling by GC–MS identified 117 compounds, and OAY exhibited the greatest total volatiles (523.02 μg/kg), exceeding OY (397.43 μg/kg) and OAM (195.73 μg/kg), indicating improved aroma complexity and consumer acceptability. In conclusion, our study will provide quantifiable formulations for the development of highly acceptable oat and almond-based plant-based yoghurt. Most importantly, it also offers additional dairy products for individuals with gluten allergies and lactose intolerance.