Intragastric gelation of whey protein–pectin alters the digestibility of whey protein during in vitro pepsin digestion

Abstract

The aim of this work is to investigate the effect of pectin on in vitro digestion of whey protein. Digestion of heated whey protein isolate (WPI) and pectin solutions (WPI-pectin) as influenced by pectin concentration and pH was studied under simulated gastric conditions. Electrophoresis, dynamic light scattering, colorimetric measurements, and gel microstructures were used to study the digestion pattern. At low pectin concentration (0.25% w/w), pectin did not significantly influence the degradation of whey protein. Increasing the pectin concentration to 1% led to extensive intragastric gelation immediately after mixing with simulated gastric fluid. The microstructure of intragastric gel from WPI-pectin at pH 6.0 showed a more interconnected and denser gel network than that at pH 7.0. More protein and pectin were involved in the gelation at pH 6.0 than pH 7.0. The digesta of samples at pH 6.0 was mainly composed of peptides, while that at pH 7.0 mostly consisted of aggregates and crosslinked peptides. This study suggests that WPI-pectin at high biopolymer ratio formed intragastric gel in simulated gastric models, which could delay protein digestion and potentially slow gastric emptying and promote satiety.