Effect of non-starch polysaccharides on the in vitro gastric digestion of soy-based milk alternatives

Non-starch polysaccharides (NSPs) are usually used as a thickener/stabilizer in food systems. Although NSPs are not digestible, they may impact the physicochemical behavior of gastric digestion. Various types of NSPs (anionic and neutral) with different molecular weights (Mw), including alginates, pectin, and guar gum, were incorporated into soy-based milk alternatives (SBMAs) at 0.2 or 0.1 wt% concentrations. The samples were digested by a semi-dynamic gastric model for 85 min, and their gastric behavior, microstructural changes, and emptying pattern of proteins were investigated. The length-scale dependent structural feature of gastric coagula determined the emptying rate. Soy proteins aggregated and formed large curds in the gastric vessel. The addition of NSPs led to fragmented curds, which emptied earlier. Confocal images revealed that embedded oil bodies coalesced within the protein coagula. High-Mw alginate formed gel particles in the gastric vessel. Soy proteins and pectin formed compact aggregates, emptying uniformly during digestion. Guar gum generated micro-phase separated small aggregates emptying at early stages of digestion. The Mw of polysaccharides, irrespective of their surface charge, significantly influenced the protein emptying rate by interfering with the growth of protein aggregates. The nutrient delivery rates of protein-stabilized emulsions can be controlled through the rational addition of NSPs with different physicochemical properties.