Modulation of Biofunctional and Structural Properties in Stevia-Sweetened Ice Cream by Lactic Fermentation

This study investigated the viability of probiotic Bifidobacterium animalis subsp. lactis and Lactobacillus gasseri in a dietetic ice cream matrix. Four formulations were produced: control (A), B. animalis subsp. lactis (B), L. gasseri (C), and a coculture of both strains (D). A synbiotic frozen system was developed using a milk-based cocoa matrix, and the cold adaptation of probiotic cells was monitored in the presence of phenolic-stevia-based cryoprotective components. Samples were analyzed before freezing, after freezing, and during 60 days of storage. Bacterial viability was assessed in the synbiotic ice cream matrix together with physicochemical properties (pH, texture, color, and organic acid formation), phenolic, antioxidant capacity (CUPRAC, DPPH), and sensory characteristics. Although a decrease in viable cell counts was observed during storage, levels remained above the recommended minimum threshold (≥ 6 log₁₀ cfu g^-1), indicating the maintenance of probiotic functionality. Microbial counts were positively correlated with lactic acid production, textural parameters (penetration and adhesiveness), and sensory attributes, such as sourness and fermented milk flavor. The synbiotic fermented system exhibited higher antioxidant capacity. Sensory evaluation showed that all fermented ice cream samples achieved acceptable scores (> 4 on the hedonic scale), indicating good consumer acceptability throughout storage. Overall, the findings suggest that the stevia-sweetened cocoa ice cream matrix can serve as a promising synbiotic frozen carrier for maintaining probiotic viability during 60 days of storage, while retaining acceptable functional and sensory quality.