Layer (whey protein isolate) -by-layer (xanthan gum) microencapsulation enhances survivability of L. bulgaricus and L. paracasei under simulated gastrointestinal juice and thermal conditions

In the study, Lactobacillus delbrueckii subsp. bulgaricus (L. bulgaricus) and Lactobacillus paracasei subsp. paracasei (L. paracasei) were isolated from food products and identified. The probiotics were co-encapsulated by emulsification technique with transglutaminase-induced gelation of whey protein isolate (WPI). A double layer was formed by xanthan gum (XG). The survival of both free and microencapsulated cells in each step was enumerated. The results showed that high entrapment yield (86.36 ± 1.07%) was achieved, WPI-XG provided significant protection for cells in simulated gastric juice and bile tolerance tests compared with free cells. Besides, the survivability under thermal condition also strengthened. During freeze-drying process, the survival was improved and naked cells cannot be seen on microcapsules surface when trehalose was added into WPI solution as a lyoprotectant. Additionally, the structure changes of WPI/XG in the encapsulation process were investigated by Fourier transform infrared spectrophotometer (FT-IR) and the thermal properties were studied by differential scanning calorimetry (DSC).