Comparative study of the viability of free and encapsulated Lactobacillus acidophilus LA02 under simulated gastrointestinal and food system conditions

This study investigated the combined effects of drying method, wall material ratio and concentration, and green tea extract addition on the technological performance and simulated gastrointestinal survival of microcapsules containing Lactobacillus acidophilus . Microcapsules were produced by freeze-drying and spray-drying using different maltodextrin and gum arabic ratios and evaluated for viability, yield, encapsulation efficiency, storage stability, structural characteristics, and resistance under simulated gastrointestinal conditions. Freeze-drying preserved probiotic viability more effectively than spray-drying. Post-encapsulation counts after freeze-drying ranged from 8.23 to 8.54 log CFU/g, with encapsulation efficiencies above 93%. In contrast, spray-dried samples showed lower counts (7.59-8.30 log CFU/g) and reduced yields (42-62%), despite efficiencies exceeding 86%. Under simulated gastrointestinal conditions, free cells showed a reduction of approximately 3.7 log units, resulting in final viability of about 61%. Freeze-dried formulations with maltodextrin-gum arabic ratios (8:2 and 5:2) maintained survival rates above 90% throughout gastrointestinal stages, whereas spray-dried samples exhibited lower ileal counts (4.6–5.7 log CFU/g). The addition of green tea extract further improved probiotic survival, particularly in optimized freeze-dried systems. Fourier transform infrared spectroscopy and scanning electron microscopy supported the structural interpretation, indicating improved matrix vitrification, reduced structural defects, and enhanced oxygen barrier properties in polymer formulations. Although encapsulation efficiency remained high after processing, simulated gastrointestinal exposure significantly reduced viable counts, highlighting the importance of matrix composition in controlling protection. Overall, probiotic performance depended on the integrated interaction between drying method, polymer ratio, and antioxidant incorporation, providing practical formulation criteria for robust probiotic ingredients with enhanced gastrointestinal resistance. • Optimized maltodextrin–gum arabic ratios ensured >90% survival during digestion. • Freeze-dried capsules formed amorphous, low-aw matrices with high probiotic stability. • Encapsulation increased resistance to heat, pH, salt, and osmotic food stresses. • Integrated processing–digestion–storage assessment guides functional food design.