Enhanced viability of Lacticaseibacillus paracasei under storage and gastrointestinal conditions by electrostatic spray drying: Effects of polysaccharide type and concentration

The encapsulation material is crucial for the storage and gastrointestinal delivery performance of probiotic microcapsule. This study investigated the physical properties, structural characteristics, storage, and digestive stability of Lacticaseibacillus paracasei K56 ( L. paracasei K56) encapsulated in a matrix composed of whey protein isolate (WPI) and three polysaccharides using the recently developed electrostatic spray drying technique. Microscopic observations indicated that L. paracasei was successfully encapsulated, and the surface of the microcapsules were smooth and crack-free. Fourier-transform infrared spectroscopy and molecular docking results revealed that hydrogen bonding and van der Waals forces are the primary interactions between WPI and the polysaccharides. All microcapsules exhibited high encapsulation efficiency (>96%) and viable cell counts (>9.7 Log CFU/g). Compared with WPI microcapsules, the addition of three polysaccharides to the microcapsules enhanced the survival ability of L. paracasei after heat treatment, storage, and in vitro digestion. In general, as the concentrations of curdlan and gum arabic in the wall material increased, the survival rates of L. paracasei gradually increased. Conversely, increasing concentrations of pullulan gradually had adverse effects. Among these formulations, the protective effect of WPI-curdlan microcapsules exhibited a stronger protective effect than WPI-pullulan and WPI-gum arabic microcapsules. After storage at 25 °C for 12 weeks, the survival rate exceeded 88%, and the viable cell count after digestion exceeded 6.4 Log CFU/g. In conclusion, this study demonstrates that WPI and CUR can serve as effective wall materials, thereby protecting cells during drying, thermal treatment, storage, and digestion.