Classification and measurement of nutritionally important starch fractions.

For nutritional purposes, starch in foods may be classified into rapidly digestible starch (RDS), slowly digestible starch (SDS) and resistant starch (RS). RS may be further divided into three categories according to the reason for resistance to digestion. A method is reported for the measurement of total starch, RDS, SDS, RS and three RS fractions in starchy foods, using controlled enzymic hydrolysis with pancreatin and amyloglucosidase. The released glucose is measured by colorimetry, using a glucose oxidase kit. Values for RDS and SDS in foods obtained by the method reflect the rate of starch digestion in vivo. Values for RS are similar to the amounts of starch escaping digestion in the small intestine of ileostomates, and are a guide to the amounts of starch likely to enter the colon for fermentation. Results are given for a number of starchy foods.