Characterization of different stages of Maillard reaction in soy: impact on physicochemical properties and immunogenicity of soy proteins

The Maillard reaction (MR, glycation) frequently occurs during processing of soy-based products widely consumed in Western diets. MR leads to the formation of a number of chemically different structures called Maillard reaction products (MRPs), which include early glycation products and advanced glycation end products (AGEs). AGEs/MRPs were shown to modulate the immune response by interaction with specific receptors expressed on immune cells, such as the receptor for advanced glycation end products (RAGE). However, the structure-function relationship of MRPs formed during soy processing in relation to binding to AGE receptors has not been well studied. The aim of the present study is to characterize the MRPs formed during different heating times of soy proteins (SP) with glucose by analyzing the biochemical changes and to relate them to the functional changes, including binding to AGE receptors and stimulating immune cells. Our results demonstrated time-dependent differences in the biochemical characteristics of glycated SP compared with heated SP, which could be attributed to the different stages of MR and the diversity of MRPs. Moreover, the formation of AGEs over time was positively correlated with binding capacity to AGE receptors. Additionally, stimulating peripheral blood adherent monocytes with glycated SP resulted in increased gene expression levels of pro-inflammatory cytokines (IL-1β, IL-8 and TNF-α) when compared to non-glycated SP, suggesting that the formed AGEs bind to and activate receptors, such as RAGE. Our findings highlight the importance of studying immunomodulation upon processing of SP, which may lead to optimisation of the processing conditions of soy based food products.