A dual strategy for selenium fortification: Probiotic fermentation and tannic acid–based microencapsulation in apple juice

This study developed a selenium-fortified functional apple juice by combining Lacticaseibacillus paracasei fermentation with tannic acid (TA)-based self-assembled microencapsulation. Results showed that fermentation with strain CICC 20241 reduced malic acid by 91.6% via malolactic conversion, significantly improving flavor and antioxidant capacity. Meanwhile, strain CICC 20975 was encapsulated to form selenium-rich microcapsules, which improved probiotic survival to 69.7% in simulated intestinal fluid. The final fortified juice achieved a selenium content of 25.85 μg/100 mL and maintained high probiotic viability and physicochemical stability over 32 days of storage at 4 °C. This dual strategy effectively addresses the instability of probiotics in low-pH fruit juice matrices, offering a precise technological approach for designing functional beverages with co-delivery of bioactive selenium and probiotics.