Assessment of the effects of oligosaccharide supplementation on the structure of lactic-fermented soy protein gel and its allergenic epitopes

The specific structural configurations and allergenic epitopes of soy protein are primary factors triggering soy allergies. Probiotic fermentation and oligosaccharide addition can alter the structure of soy protein, regulating its changes during gastrointestinal digestion and thus affecting the allergenicity of soy protein. This study prepared soy protein gels (FSPIs) through fermentation by lactic acid bacteria (LAB). The gels incorporated five types of oligosaccharides (fructooligosaccharide (FOS), xylooligosaccharide (XOS), stachyose (SOS), galactooligosaccharide (GOS), and isomaltooligosaccharides (IMO)). Moreover, this work investigated the effects of different oligosaccharides on soy protein gel structure and conducted in vitro dynamic gastroduodenal digestion and in vivo animal models to determine the changes in the allergenicity of the gel samples. Peptidomics were applied to determine the degradation of linear allergenic epitopes. Results showed that the type of oligosaccharides influenced the texture and microstructure of the FSPIs, affecting digestive behaviors. The samples added with FOS (F-FOS) and XOS (F-XOS) showed low-hardness, demonstrating weak structures, whereas the samples with SOS (F-SOS), GOS (F-GOS), and IMO (F-IMO) displayed high-hardness, strong sheet structures. Additionally, allergenicity and peptidomics results indicated that the F-FOS and F-SOS exhibited low antigenicity and IgEbinding capacities at both 120 min of in vitro digestion and in vivo mice studies, and particularly promoted extensive degradation of the sensitizing epitopes located on the external regions of the glycine G2/G5 subunits and the core barrel domain of the (3-conglycinin alpha and (3 subunits. This study suggests that using oligosaccharides with LAB to create soy protein gels is a promising strategy for developing hypoallergenic plant protein matrices.