Viability of Microencapsulated Lactobacillus acidophilus LA5 with Yeast Cell Wall and β-Glucan in Synbiotic Doogh (Iranian Yogurt Drink) under Simulated Gastrointestinal Conditions

This study examined whether spray-dried microcapsules can preserve Lactobacillus acidophilus LA-5 in a real food matrix. Three wall systems were compared: 1.5 % sodium alginate (Alg), 1.5 % alginate supplemented with 3% yeast cell wall (Alg-Y3), and alginate 1.5 % with 5% β-glucan (Alg-βGlu5). Microcapsules (initial loading 109 CFU/mL-1) were incorporated into Doogh (Iranian yogurt drink) and stored at 4 °C for 28 days. Probiotic viability, physicochemical parameters (pH, titratable acidity, apparent viscosity, phase separation/sedimentation) and sensory acceptance were monitored; selected samples were also challenged in simulated gastric and intestinal fluids. Microencapsulation markedly reduced viability loss during refrigerated storage and substantially improved tolerance to gastrointestinal-like stress compared with free cells. The Alg-Y3 system delivered the best overall performance, retaining >7 log CFU/mL-1 at the end of storage and showing the highest survival after sequential SGF/SIF exposure, while free cells fell below functional levels. Alg-βGlu5 increased apparent viscosity but did not impair consumer acceptance. Importantly, incorporation of the optimized microcapsules into Doogh did not adversely affect sensory scores. These findings indicate that alginate co-formulated with yeast cell wall or β-glucan offers a practical route to produce synbiotic fermented beverages with improved probiotic stability and gastrointestinal delivery.