Effects of Pea Protein Fortification, High-Pressure Homogenization and Probiotic Fermentation on the Nutritional, Technofunctional, Sensory and In Vitro Digestive Properties of a Peach–Grape Juice Beverage

This study characterized a protein-fortified peach-and-grape beverage, focusing on the effects of fermentation and protein particle size on protein digestibility and the bioaccessibility of minerals and antioxidants. Beverages were formulated with 3.5% pea protein isolate (PPI), added directly to peach-and-grape juice (PGJ) or subjected to high-pressure homogenization (HPH) before incorporation. The resulting beverages (PGJ + PPI and PGJ + PPIHPH) were evaluated before and after lactic fermentation for 48 h. HPH significantly reduced PPI particle size while increasing polyphenol content (11.27%) and antioxidant activity (ABTS: 11.09%; FRAP: 12.83%). Fermentation resulted in the detection of glutamine (1.32 ± 0.23 mg/g d.w.) and increased lactic acid content (61.44 ± 0.83 mg/g d.w.) and the levels of the essential amino acids phenylalanine and valine. Both fermentation and HPH increased the readily bioaccessible hydrolyzed protein fraction (13.27% and 11.94%, respectively), although neither significantly affected mineral or antioxidant bioaccessibility. Probiotic viability during fermentation and simulated gastrointestinal digestion was assessed using viable counts, with the quantitative results needed to establish the extent of viability retention. However, fermented beverages showed lower consumer acceptability. Overall, protein fortification and fermentation improved selected nutritional and in vitro digestive properties, although fermentation adversely affected sensory acceptance. These findings highlight the need to balance nutritional and functional improvements with consumer acceptability in the development of fermented, protein-fortified plant-based beverages.