Characterization of whey protein isolate-gum Arabic Maillard conjugate and evaluation of the effects of conjugate-stabilized emulsion on microbiota of human fecal cultures

Protein-polysaccharide conjugates formed by the Maillard reaction can be used as novel emulsifiers in the emulsion systems. However, understanding of the regulatory effects of the Maillard conjugates on gut microbiota is limited. The purposes of this work were to prepare a novel emulsifier (WPI-GA-C) formed by conjugation of whey protein isolate (WPI) and gum Arabic (GA) via the dry heating method and to investigate the effects of WPI-GA-C-stabilized emulsion on human gut microbiota. The changed characteristics including color, aroma profiles, chemical bonding interaction, as well as secondary and tertiary structures, confirmed the formation of Maillard conjugate. WPI-GA-C-stabilized emulsion could significantly modulate the composition and abundance of gut microbiota. At the phylum level, WPI-GA-C-stabilized emulsion decreased the ratio of Firmicutes to Bacteroidetes whereas increased the relative abundance of Actinobacteria. At the species level, Bacteroides ovatus and Bifidobacterium longum, the considered potential probiotics, were significantly enriched. The results of Phylogenetic Investigation of Communities by Reconstruction of Unobserved States analysis indicated that WPI-GA-C-stabilized emulsion significantly enriched the pathways of carbohydrate metabolism and bile acid biosynthesis. These results demonstrated that the novel emulsifier prepared by the Maillard reaction showed the potential to promote healthy changes in human gut microbiota, which have important implications for designing emulsion delivery systems using the protein-polysaccharide conjugates as the emulsifiers.