Comprehensive evaluation of d-allulose on the quality, flavor profile, and probiotic viability in Lacticaseibacillus rhamnosus GG fermented milk.

d-Allulose has emerged as a promising sucrose substitute, yet its impact on the quality of probiotic fermented milk is not well understood. This study evaluated the effects of d-allulose on the viability, physicochemical properties, texture, stability, sensory quality, and volatile profile of fermented milk produced with Lacticaseibacillus rhamnosus GG and Streptococcus thermophilus. d-Allulose was incorporated at levels of 0% to 10%. With this range, d-allulose maintained the viability of both strains in fermented milk. Among the tested treatments, moderate supplementation, particularly at 3%, was associated with the greatest acidification, favorable textural properties, and the highest overall sensory acceptability. Volatile analysis further indicated that replacing sucrose with d-allulose reshaped the aroma profile, reducing the contribution of some fruity and green-related odorants while enhancing buttery and creamy aroma-associated ketones in the moderately supplemented samples. Overall, these findings indicate that moderate d-allulose supplementation, especially at 3%, may improve the overall quality of probiotic fermented milk and support its potential application as a sucrose alternative in lower-calorie fermented milk products.