Effect of pre-culture incubation duration on the physicochemical and microbial properties of vegan yogurt

At present, the consumption trend of plant-based nutritional products is becoming increasingly widespread, particularly among individuals with lactose intolerance or milk allergies. This study aimed to develop a plant-based yogurt using purple rice supplemented with soymilk, focusing on optimizing fermentation efficiency and product quality. The effects of varying commercial yogurt starter culture concentrations (0.5 %, 1.0 %, 1.5 % and 2.0 %) and pre-culture incubation durations (8, 16, 24, 32, 40 and 48 hr) were investigated. Bacterial density, fermentation time, lactic acid production and water-holding capacity of the yogurt were checked as the observed criteria. With a 1.5 % inoculum ratio pre-culture incubated within 32 hr, which was selected as the optimal condition ensuring betweenfermented efficiency and yogurt quality. Applying this condition, the bacterial concentration achieved 5.81 × 108 (cfu/mL), the fermentation duration was shortened to 360 min and the water-holding capacity (WHC) reached its maximum value at 94.66 %, presenting a well-formed gel texture with high flocculation and enhanced sensory attributes. This paper provided a practical approach for economical production of high-quality plant-based yogurt from unutilized crops.