Construction of double network gel for co-encapsulation of probiotics and capsaicin: Enhanced the physicochemical stability and controlled release

Probiotics and capsaicin, as common hydrophilic and hydrophobic bioactive ingredients, are extremely sensitive to environmental stress. We used a one-step gelation strategy to co-encapsulate Lactobacillus rhamnosus GG (LGG) and capsaicin in a gel of whey protein isolate (WPI)-stabilized emulsion and shellac induced by glucono-δ-lactone (GDL) and CaCl 2 to solve this problem. Shellac was first induced by CaCl 2 to rapidly form a gel in a short time. Then, WPI-stabilized oil droplets were slowly covalently cross-linked by GDL and then embedded into the shellac gel network. Phase permeation behavior of the two biopolymers during gelation formed a tight microstructure through hydrophobic interactions and disulfide bonds. Results showed that the gel with 1.5% GDL and 4% shellac had the densest microstructure, maintained good integrity during in vitro digestion, and effectively controlled the release of capsaicin and LGG. Furthermore, the gel exhibited superior protection under harsh conditions such as heat, freezing, and storage: up to 7.76 log cfu/g of LGG and 66.26% of capsaicin were retained after 15 days of storage. Interestingly, capsaicin, as an antioxidant, may provide additional protection to the storage stability of LGG by reducing oxidative damage of cell membrane. This study provided a new perspective for designing co-delivery systems of hydrophobic and hydrophilic compounds.