Interpenetrating polymer network hydrogels of soy protein isolate and sugar beet pectin as a potential carrier for probiotics

In present study, a combination of biopolymers soy protein isolate (SPI) and sugar beet pectin (SBP) has been used to prepare an interpenetrating polymer network (IPN) hydrogel by enzymatic method. The obtained results showed that the rheological properties, textural properties and swelling properties could be tuned by regulating the concentrations of SPI and SBP as well as the amount of laccase. Moreover, the incorporation of probiotic Lactobacillus paracasei LS14 resulted in a decrease of storage modulus (G′) and hardness of SPI/SBP IPN gels. The reason might be that the addition of probiotics caused the exposure of tryptophan-containing extension regions within SPI molecules to a more polar environment. In addition, the occurrence of steric-hindrance effect of probiotic cells during the gelation of IPN hydrogels retarded the formation of covalent cross-links or physical interactions between biopolymer molecules. Scanning electron microscopy (SEM) observation confirmed that the presence of probiotics slightly disrupted the ordered microstructure of the IPN hydrogel. Under simulated gastrointestinal conditions, the SPI/SBP IPN gel showed its advantage in protection of Lb. paracasei LS14 since it had higher viabilities of probiotic cells as compared to free cells. In addition, lyophilized gels exhibited better storage stability but lower probiotic viability in comparison to wet gels. Overall, this study explored a novel method for the production of SPI/SBP IPN gel as a delivery system for probiotics, which would have great potential for development of probiotic-containing foods.