Involvement of the protein network in the in vitro degradation of starch from spaghetti and lasagne: a microscopic and enzymic study

This study aimed to determine the involvement of the protein network in the in mire degradation of starch from intact pasta strands. The physical structure of pasta was characterised during enzymic treatment by microscopy, and hydrolysis kinetics were interpreted. When incubated with human salivary alpha-amylase (HSA), the protein network remained intact, retarding starch degradation. The presence of proteases contaminating pig pancreatic a(pha-amylase contributed to the partial hydrolysis of the protein network (similar to the effect of pepsin), increasing starch degradation after 1 h of alpha-amylolysis in comparison with HSA. Complete accessibility of starch to alpha-amylase after 72 h of alpha-amylolysis was demonstrated by chromatography, both with intact and degraded protein networks. Two hours pre-treatment of pasta with pepsin or HSA increased respectively the initial degradation of starch and protein. Starch or protein presence, therefore, hinders the action of the enzyme, which does not degrade it. The protein network is not itself a physical barrier to alpha-amylase access to starch in pasta. Both microscopy and hydrolysis kinetics have revealed that new physico-chemical factors related to food structure should be considered in the enzymic degradation of pasta. (C) 1998 Academic Press Limited.