ENZYMIC SUSCEPTIBILITY OF STARCH FROM PASTA

The aim of this work was to study the structural factors of pasta products that are responsible for their low glucose and insulin responses and incomplete intestinal absorption of starch in healthy subjects. Native starch extracted from durum wheat in the laboratory was used as reference. Starch granules in pasta of different sizes, cooked for different time periods, were completely gelatinized, as proved by differential scanning calorimetry and X-ray diffraction. Compared to native starch, susceptibility to α-amylase hydrolysis was always increased by cooking. Complete solubilization into oligosaccharides was obtained in 24 h for enzyme concentrations higher than 600 nkat/ml with 17 mg starch per ml. Smaller pasta size and increased cooking time led to higher susceptibility. When pasta structure was destroyed by grinding, starch was solubilized completely in less than 30 min by α-amylase hydrolysis. Limited swelling of starch granules during cooking and encapsulation by the protein network were partly responsible for the slow amylolysis kinetics. An estimation of the susceptibility towards α-amylase of gelatinized starchy products is proposed, based on the minimal concentration of α-amylase necessary to obtain the solubilization of the easily degradable fraction. © 1990, Academic Press Limited. All rights reserved.