Measurement and Characterization of Dietary Starches
Some factors present in the starchy foods influence the rate at which the starch is hydrolysed and absorbed in vivo. In order to predict the physiological effects of starchy foods and to complement information of food composition database, the quantification and characterization of the various components in the starch fraction must be evaluated. The contents of total starch (TS), resistant starch (RS), digestible starch (DS), amylose and dietary fibre (DF) were evaluated in 11 starchy foods cooked and cooked/stored (-20°C/30 days—conventional and domestic storage). The in vitro starch hydrolysis, the hydrolysis index (HI), rapidly digestible starch (RDS) and slowly digestible starch (SDS) were also carried out with the same samples. These storage conditions increased the RS content and decreased the HI in all studied foods, and each food showed a specific behaviour in relation to each variable. The high concentration of amylose is not the only fact involved with the starch retrogradation and the formation of RS. Therefore, the complete characterization of the starch fraction of foods subjected to different ways of preparation and storage conditions should be included in the food composition database. The highly significant positive correlation observed between the HI and RDS (y=0.573x-16.671, r=0.907, P0.001, n=22) suggests that the RDS, expressed as dry weight, is an alternative device to predict the digestion of starchy foods.
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