Development of a novel protein and calcium fortified plant-based yogurt by addition of pea protein isolate and bio-calcium from Nile tilapia bones

Abstract The aim of this study was to develop plant-based yogurt from a mixture of waxy corn and soy milks that mitigated the nutritional deficiencies of typical plant-based products with desirable sensory characteristics and nutritional value by fortifying them with pea protein isolate (PPI) and bio-calcium (Bio-Ca) from Nile tilapia bone. Firstly, different concentrations of PPI (1.0%, 3.0%, and 5.0%) were applied to enhance protein content of plant-based yogurt. Their impacts on the fermentation, physicochemical, and sensory characteristics of developed plant-based yogurts were studied. During fermentation at 40 °C (14 h), the pH of PPI-supplemented samples was higher than that of the control (without PPI) in the first period of fermentation (0–6 h), indicating buffering property of PPI. Titratable acid content (TTA) of yogurt with PPI showed higher TTA than control (p < 0.05) after 14 h of incubation. With good acceptance (score ≥ 6) and high protein content (5.41%), the yogurt with 5% PPI was then selected for a study on Bio-Ca fortification. The results showed that adding Bio-Ca (0.5%, 1.0%, and 1.5%) changed the way yogurt fermented and its physical and chemical properties, especially when Bio-Ca levels were higher than 0.5%. After fermentation, the sample with Bio-Ca exhibited a higher total titratable acidity (TTA) and increased viscosity, indicating enhanced metabolic activity of lactic acid bacteria and the formation of salt bridges, respectively, due to Bio-Ca. Sensory evaluation showed that the addition of Bio-Ca had no adverse effect on all attributes tested. In addition, fortification of Bio-Ca at 1.5% showed that calcium content in yogurt was 206.5 mg/100 g sample. Thus, yogurt with 5.0% PPI and 1.5% Bio-Ca was selected for stability evaluation under cold storage for 21 days. The selected yogurt showed a great stability with > 6 log CFU/mL of probiotics throughout the storage period with a lowered syneresis (78.8%), compared with control (72.0%) (p < 0.05). This study emphasizes a novel formulation of plant-based yogurt, which provides a rich source of protein and calcium, thereby suggesting its potential advantages over both conventional dairy and plant-based yogurts. Graphical Abstract