The effect of nanochitin on gastrointestinal digestion of starch and protein: Role of surface charge and size

Abstract

The effects of three different kinds of nanochitin, namely amino-rich partially deacetylated nanochitin (PD-ChNF, length of ∼800 nm; and PD-ChNC, length of ∼500 nm), and carboxyl-rich TEMPO oxidized nanochitin (TO-ChNF, length of ∼400 nm) on nutrient digestion and absorption in vitro were investigated. All the nanochitin gelated in a simulated vitro environment and did not affect the activities of pepsin, trypsin and pancreatic amylase. During digestion process, nanochitin delayed the hydrolysis of starch and protein and inhibited the release/diffusion of glucose and free amino nitrogen by gelation wrapping. Positively charged nanochitin showed better reduction effect on starch digestibility, 4% PD-ChNC significantly decreased starch digestibility by 23% and glucose diffusion from 583 to 386 μmol; while, 4% TO-ChNF had a greater effect on protein digestibility, free amino nitrogen released in stomach was decreased from 358 to 129 μmol. The results demonstrated that nanochitin could be used as dietary fiber either to delay starch digestion and control postprandial blood sugar elevation or to affect protein digestion through physical encapsulation, whereby the accessibility of the digestive enzyme to chyme was inhibited.