Compact structure and proteins of pasta retard in vitro digestive evolution of branched starch molecular structure

The roles that the compact structure and proteins in pasta play in retarding evolution of starch molecular structure during in vitro digestion are explored, using four types of cooked samples: whole pasta, pasta powder, semolina (with proteins) and extracted starch without proteins. These were subjected to in vitro digestion with porcine alpha-amylase, collecting samples at different times and characterizing the weight distribution of branched starch molecules using size-exclusion chromatography. Measurement of alpha-amylase activity showed that a protein (or proteins) from semolina or pasta powder interacted with alpha-amylase, causing reduced enzymatic activity and retarding digestion of branched starch molecules with hydrodynamic radius (R-h) < 100 nm; this protein(s) was susceptible to proteolysis. Thus the compact structure of pasta protects the starch and proteins in the interior of the whole pasta, reducing the enzymatic degradation of starch molecules, especially for molecules with R-h > 100 nm. (C) 2016 Elsevier Ltd. All rights reserved.