In this research, the emulsification method was used to encapsulate Lactobacillus reuteri in microparticles of whey protein concentrate (WPC) at different levels (1%, 2%, and 4%) and gum Arabic (GA) at three levels (0/5%, 1%, and 1/5%) and a constant level of sunflower oil (5%). The results showed that emulsions with higher quantities of wall materials exhibited better encapsulation efficiency (67%/57%) and preservation ability at different temperatures, different pH, and presence of 1% bile salt. During the storage time, the droplet size of the emulsion increased more than two times (from 2.2 to 4.6 μm) and the absolute zeta potential of the optimal emulsion decreased (from −19/63 to −16/76 mV). Encapsulating Lactobacillus reuteri in the stabilized emulsion with the highest concentration of wall material improved the cells\\\\\\\\\\\\\\\' protection during storage. The study also observed a decline in the number of primary encapsulated live cells in the gastrointestinal tract (from 4/32 to 3/58 Log CFU/mL) after 90 days of storage. In the case of the nonencapsulated sample, the initial live population decreased from 2.8 to 1 Log CFU/mL after 90 days of storage. The electron microscope images showed that the emulsions became unstable after 30, 60, and 90 days of storage, but the microbial cells were still visible in the continuous phase. Overall, encapsulating Lactobacillus reuteri using emulsification technique can preserve the probiotics during storage and “in vitro” gastrointestinal digestion.

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