Effect of Ultrasonication on the Physicochemical Properties and Stability of a Fermented Almond Beverage Added With Microencapsulated Lacticaseibacillus casei ATCC 334

The growing demand for probiotic plant-based beverages presents challenges, particularly regarding physical stability. Ultrasonication has emerged as a promising technology to enhance the stability and functionality of such products. This study is aimed at developing an almond-based probiotic beverage using ultrasonication and evaluating its impact on physicochemical and functional properties. Two ultrasonication amplitudes (40% and 80%) were applied to almond extracts, which were then inoculated with free cells of Lacticaseibacillus casei ATCC 334 and incubated at 37°C for 6 h. The 40% ultrasonication treatment improved phase separation stability and significantly increased antioxidant activity, from 22.79 ± 3.9% (untreated) to 30.01 ± 2.19%, and further to 38.46 ± 1.06% in the ultrasonicated and fermented sample. Three types of fermented almond beverages were prepared using the 40% ultrasonicated extract inoculated with yogurt starter cultures and Lb. casei in different forms: free cells (LCF), whey protein microencapsulated cells (LCW), and phosphate starch with inulin microencapsulated cells (LCI). Probiotic viability was monitored during fermentation, 28-day cold storage, and simulated gastrointestinal (GI) exposure. The LCI treatment showed a significant increase in probiotic cell counts during fermentation. No significant differences in viability were observed among treatments during storage. Microencapsulation with whey protein and phosphate starch–inulin effectively reduced postacidification. After simulated GI exposure, LCF showed the greatest cell loss (~5.1 log CFU/mL), while LCW and LCI exhibited improved survival (3.0 and 3.27 log CFU/mL loss, respectively). Based on rheological properties, LCW had the highest initial apparent viscosity, whereas LCI maintained greater stability at a constant shear rate (25°C). Overall, ultrasonication combined with fermentation improved the antioxidant capacity, probiotic viability, and physical stability of almond-based probiotic beverages, supporting its application in developing functional plant-based products.