Thermal Abuse and Age of Biomass as Critical Factors for the Viability of Functional Microorganisms in “Fiordilatte” Ice Cream

ABSTRACT This study investigated the viability during storage, adhesion properties, and survival during simulated gastrointestinal transit of Lactiplantibacillus plantarum c19 and Bifidobacterium longum subsp. infantis DSM 20088 incorporated into “Fiordilatte” ice‐cream, with a focus on the effects of thermal abuse and biomass age. A multifactorial experimental design was applied, including the number of thawing cycles (1–3 cycles at 25°C), their duration (2–6 h), and cell age (15, 24, and 72 h). Biomass age was the most critical factor affecting probiotic survival: 72‐h‐old cultures showed a significant reduction in viability (approximately 1.0–1.9 log CFU/g) compared to 15‐ to 24‐h‐old cultures ( p < 0.05). Moreover, thawing/refreezing cycles affected viability only in interaction with cell age. Both strains demonstrated strong resistance during simulated gastrointestinal transit, with final concentrations above 7 log CFU/g, and high adhesion capacity, indicating their potential for stable intestinal colonization. Sensory scores were not affected, and the overall scores were between 7.5 and 8.1 without significant differences due to probiotic addition. Overall, these results confirm that ice cream can serve as an effective delivery matrix for probiotics, provided that critical parameters, such as biomass age and strict control of thermal conditions during production and storage, are carefully managed.