Validation of Layer-By-Layer Coating as a Procedure to Enhance Lactobacillus plantarum Survival during In Vitro Digestion, Storage, and Fermentation

Probiotics are sensitive to phenolic antibacterial components and the extremely acidic environment of blueberry juices. Layer-by-layer (LbL) coating using whey protein isolate fibrils (WPIFs) and sodium alginate (ALG), carboxymethyl cellulose (CMC), or xanthan gum (XG) was developed to improve the survival rate of Lactobacillus plantarum 90 (LP90) in simulated digestion, storage, and fermented blueberry juices. The LbL-coated LP90 remained at 6.65 log CFU/mL after 48 h of fermentation. Scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) indicated that dense and rough wall networks were formed on the surface of LP90, maintaining the integrity of LP90 cells after the coating. Stability evaluation showed that the LbL-coated LP90 had a much higher survival rate in the processes of simulated gastrointestinal digestion and storage. The formation mechanism of the LbL coating process was further explored, which indicated that electrostatic interactions and hydrogen bonding were involved. The LbL coating approach has great potential to protect and deliver probiotics in food systems.

Automated summary

A layer-by-layer coating method using whey protein isolate fibrils and sodium alginate, carboxymethyl cellulose, or xanthan gum was developed to improve the survival rate of Lactobacillus plantarum in simulated digestion, storage, and fermented blueberry juices. The coated Lactobacillus remained stable after fermentation and exhibited higher survival rates in simulated digestion and storage compared to uncoated counterparts. The formation mechanism of the coating process was explored, revealing the involvement of electrostatic interactions and hydrogen bonding. This approach has great potential in protecting and delivering probiotics in food systems.