Alginate-based double-network hydrogel improves the viability of encapsulated probiotics during simulated sequential gastrointestinal digestion: Effect of biopolymer type and concentrations

The impact of secondary polysaccharide, i.e., low methoxyl pectin (LMP) or κ-carrageenan (KC), and its concentration (0.2, 0.4, and 0.6%) on particle size, shape, morphological, textural properties and swelling behavior of sodium alginate (ALG)- based double-network hydrogel particles, as well as the viability of encapsulated probiotics Lactobacillus rhamnosus GG (LGG) in simulated sequential gastrointestinal (GI) digestion was investigated. We found the addition of LMP impaired the sphericity of double-network hydrogel particles, while the incorporation of KC increased the particle size. The FT-IR results indicated the miscibility and cross-linking capacity of the two polysaccharides in forming double-network hydrogel particles. With respect to the swelling behavior in simulated GI digestion, all hydrogel particles shrank in simulated gastric fluid (SGF) but swelled in simulated intestinal fluid (SIF). Among the two types of double-networking, ALG-KC hydrogel particles showed noticeable shrank in SGF in conjunction with the reduced swelling in SIF, which was unfavorable for protection and the controlled release of probiotics. In the case of death rate of encapsulated LGG, the presence of LMP at a lower level (0.2 or 0.4%) exhibited protective effect against LGG death during the sequential GI digestion, while addition of KC demonstrated an opposite role.