The role of thermostable proteinaceous α-amylase inhibitors in slowing starch digestion in pasta.

Abstract Starch in pasta is slowly digested, which is nutritionally advantageous because it reduces post-prandial glycemia, a risk factor for type 2 diabetes. We examine the role of proteinaceous amylase inhibitors, providing insights into how wheat proteins slow starch digestion. Gluten samples were extracted in the laboratory and also commercially obtained, and incubated in water at 37 °C and 100 °C. The centrifuged supernatant and gluten pellet were incubated with porcine α-amylase, and enzymatic activity measurement revealed that the supernatant from gluten heated to 100 °C retained the capacity to significantly reduce amylolytic activity. Confocal microscopy showed that the gluten pellet had become porous following heat treatment. These results are consistent with an increased concentration of soluble proteins after cooking. Proteins in the soluble fraction and gluten pellet were identified with mass spectrometry proteomics, which screened a limited number of endogenous double-headed α-amylase/trypsin inhibitors (α-AI(s)), found to be enriched in the supernatant after cooking. Endogenous α-AI(s) play a role in slowing starch digestion by interacting with α-amylase as it penetrates the gluten network that entraps the starch, resulting in an immobilization of the enzyme onto the gluten network, so that the digestion of starch entrapped by the gluten network is inhibited. Graphical abstract Wheat gluten network contains highly thermally stable proteinaceous α-amylase inhibitors that interact and complex with the α-amylase to inhibit the starch digestion. Image 1 Highlights • Slow starch digestion in pasta is nutritionally advantageous. • Thermostable α-amylase inhibitors (α-AI(s)) present in gluten network. • Proteomics screened limited number of probable target α-AI(s). • Endogenous α-AI(s) slow starch digestion by interacting with α-amylase. [ABSTRACT FROM AUTHOR]