Novel Probiotic Frozen Yogurt Formulated with Baked Fermented Milk: Physicochemical, Microbiological, and Sensory Characteristics

Consumers increasingly favor frozen yogurt as a healthier alternative to ice cream due to its lower fat content and probiotic benefits. Baked fermented milk (BFM), with its caramelized flavor, brown color, and enhanced nutritional properties, has emerged as a promising ingredient for improving the functional and sensory qualities of frozen yogurt. This study aimed to develop a novel probiotic baked frozen yogurt (PBFY) using BFM instead of traditional fermented milk (TFM) and to evaluate its physicochemical, microbiological, and sensory characteristics compared with traditional probiotic frozen yogurt (PTFY). Reconstituted skim milk and fresh cream were heat-treated (90 °C, 5 min) for TFM or baked (115 °C, 20 min) for BFM prior to culture inoculation. Both bases were inoculated with Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus, along with the probiotic strains Lactobacillus acidophilus and Bifidobacteriumanimalis subsp. lactis. PTFY and PBFY were formulated by blending ice cream mix with TFM or BFM at 25, 50, and 75% substitution levels. Increasing fermented milk concentration significantly decreased pH and surface tension while elevating mix viscosity. High inclusion levels (75%) impaired whipping ability, reduced overrun, increased fat destabilization, decreased the melting rate, and reduced culture survival during storage. Compared with PTFY, PBFY exhibited a higher melting rate, lower viscosity, and superior antioxidant activity (1.31- and 1.33-fold higher DPPH and ABTS radical-scavenging activity, respectively); however, the fermented milk type did not significantly affect overrun or fat destabilization. During storage, S. thermophilus was the most stable strain, with a decline rate of 0.6–0.69 log10 CFU/mL/month, whereas B. animalis subsp. lactis showed a more rapid decline (0.80–0.89 log10 CFU/mL/month). Sensory evaluation revealed that a 50% BFM inclusion level was optimal, producing PBFY with a smooth texture, light brown color, and appealing caramel-like flavor.