Effect of Stevia as a Natural Sweetener on the Quality of Synbiotic Pumpkin Yogurt

Pumpkin (Cucurbita moschata) is a potential base ingredient for synbiotic yogurt to its content of antioxidant compounds and Raffinose Family Oligosaccharides (RFO), which act as prebiotics to support probiotic growth. Stevia (Stevia rebaudiana Bertoni) offers a high-intensity, calorie-free natural sweetener, making it an alternative to conventional sugar in functional fermented dairy products. This study aimed to examine the effect of stevia concentration on the quality and antioxidant activity of synbiotic yogurt made from pumpkin juice. The novelty of this research lies in the use of stevia as a natural sweetener in pumpkin-based synbiotic yogurt, while simultaneously evaluating its chemical, microbiological, and sensory properties, as well as its antioxidant activity. This experiment employed a Completely Randomized Design (CRD) with four stevia composition treatments and three replicates: P0 (0%), P1 (0.1%), P2 (0.2%), and P3 (0.3%). Data were analyzed using One-Way Analysis of Variance (ANOVA), followed by the Least Significant Difference (LSD) test at a 5% significance level. Increasing stevia concentration significantly affected pH, TTA, Lactic Acid Bacteria (LAB) count, and antioxidant activity; it lowered pH while increasing TTA and LAB counts, all within the limits of the SNI 2981:2009 standard. Stevia concentration did not significantly affect color, aroma, or texture, but it did significantly influence taste, with treatment P2 (0.2%) achieving the highest level of sensory acceptance. The highest antioxidant activity was observed in P3 (0.3%) with an IC50 value of 77,388 ppm, categorizing its antioxidant activity as strong. Overall, P3 (0.3%) was determined to be the optimal formulation based on chemical, microbiological, and antioxidant properties, as well as sensory acceptance. These findings demonstrate the practical potential of stevia as a natural sweetener for the development of low-calorie functional dairy products with synbiotic and antioxidant properties.