Consumers are becoming increasingly interested in functional foods, specifically synbiotic products, that not only provide basic nutrition but also have added health benefits. This study was conducted on soy and cow's milk yoghurts that used probiotic culture ABT7 (mixed culture: L. bulgaricus, S. thermophillus, B. animalis) and prebiotics like psyllium husk. Additionally, this study aimed to determine the effect of prebiotics and probiotics on different physico-chemical, microbial, and sensory properties of the prepared synbiotic yoghurts.

Four different formulations of soy yoghurt and cow's milk yoghurt were made using psyllium husk and probiotics, with the first batch of each serving as a control. The best formulation was chosen based on sensory attributes and the selected formulations were then physically examined and chemically analyzed for various parameters such as pH, titratable acidity, water syneresis, total soluble solid (TSS), total reducing sugar, total phenol content, total flavonoid content, total antioxidant activity, and microbial counts at different storage intervals of 1, 4, 8, and 12 days. This study found that synbiotic soy milk yoghurt, specifically with 0.5% psyllium husk, had the highest nutritional value, high viability, and high phenolic, flavonoid, and anti-radical activity, with levels ranging from 8.15 to 8.32 log cfu/ml, from 2.21 to 2.84%, 5.64 to 25.53%, and 62 to 64%, respectively, when stored for 12 days. However, based on these evaluations, it has been revealed that the synbiotic yoghurts could not be stored beyond 12 days, even at a refrigeration temperature (4°C). The potential applications of soy yoghurt as a functional food could be expanded by incorporating underutilized, fiber-rich ingredients such as psyllium husk to maximize its nutritional benefits.