In vitro starch degradation from wheat-based products in the presence of lipid complex emulsions

The lower glycemic index when lipids are coingested with starchy foods was supposed to result from several factors such as lower gastric emptying, hig her insulinic response, decreased glucose absorption through the upper smal l intestine and lower starch accessibility to alpha-amylase. This study inv estigated whether lipid/food structure interactions may play a role in limi ting starch accessibility to alpha-amylase. Three wheat-based products (whe at starch, white-wheat bread and 5-mm spaghetti strands), differing in food structure/porosity, were incubated for 8 h with human salivary alpha-amyla se (HSA) in the presence or not of two differently-sized emulsions (7.1 and 0.6 mu m) HSA-specific activity was not modified in the presence of the co arse emulsion (7.1 Gun) On the whole, regardless of the food structure, the two emulsions had no marked effect on the rate and degree of alpha-amyloly sis. However, in the presence of the fine emulsion, starch from white-wheat bread tended to be more slowly hydrolysed effect being significant (P < 0. 05) between 10 and 30 min of alpha-amylolysis. In the case of pasta, starch tended to be more rapidly hydrolysed in the presence of the coarse emulsio n with a significant effect at 4 h of alpha-amylolysis. We concluded that e mulsified lipids do not interact with complex starchy food structure of whi te-wheat bread and pasta in a way that significantly limits the action of a lpha-amylase. (C) 1999 Elsevier Science Inc.