Effect of Black Soybean Substitution and Fermentation Method (Backslope vs. Precision) on the Physical and Sensory Properties of Symbiotic Yogurt Ice Cream

The development of symbiotic frozen desserts using locally sourced plant-based ingredients remains limited, particularly the use of Indonesian Detam-1 black soybean and the comparison of different yogurt fermentation methods. This study aimed to formulate symbiotic yogurt ice cream by substituting whole cream milk with Detam-1 black soybean paste (0%, 10%, 20%) and applying two fermentation approaches: backslope and precision. A Completely Randomized Design with three replications was used. Physical evaluations included measurements of viscosity, overrun, total soluble solids, and melting time, while sensory analysis involved 40 semi-trained panelists using a nine-point hedonic scale. Data were analyzed using two-way ANOVA followed by Duncan’s test. The results showed that the fermentation method had no significant effect on any of the parameters (p > 0.05). The best physical performance was observed in the 20% substitution formula (F2), which showed the highest viscosity and a melting time of around 31 minutes for both methods. Although increasing substitution levels slightly reduced preference, the product’s overall appearance maintained a neutral to like moderately range (5.78 to 6.70). These findings indicate that Detam-1 black soybean paste has strong potential as a functional, locally plant-based prebiotic source and provides new insight into the comparative use of backslope versus precision fermentation in symbiotic frozen dessert development.