Physicochemical properties and cell viability comparison of two Lactiplantibacillus plantarum DNZ-4 microcapsules and its application in beverages

Two microcapsules of Lactiplantibacillus Plantarum DNZ-4 (DNZ-4) with shell of casein-alginate (A-CDM) and casein-alginate-chitosan (CA-CDM) were prepared by the polymeric gel and layer-by-layer (LBL) encapsulation technique. These microcapsules with an encapsulation rate of 93.17% were compared with physicochemical properties, cell viability, storage, and application. The results showed that there was no significant difference in particle size between A-CDM (2.22 mm) and CA-CDM (2.35 mm). SEM images showed that CA-CDM became more regular and smoother after chitosan coating. FTIR analysis confirmed the presence of hydrogen bonds and electrostatic interactions in CDMs. The interaction between chitosan and alginate made the swelling ratio significantly lower than A-CDM in simulated gastric and intestinal fluid. Both microcapsules significantly improved cell viability under high temperature, low acidity, bile salts, storage, and gastrointestinal digestion, and CA-CDM demonstrated a better protective effect than A-CDM. The number of viable cells in beverages reduced by only 1.74 lg CFU/mL due to the protective effect of CA-CDM after pasteurized (63 °C, 30 min). Moreover, the cell counts were all above 7 lg CFU/mL stored at 4 °C for 28 days, and the pH and viscosity of the beverages changed slightly. Therefore, multilayer-coated microcapsules with casein-alginate-chitosan have great potential in protecting probiotics, target delivery, and applications.