Significant proportion of starch in the normal diet
A significant proportion of starch in the normal diet escapes degradation in the stomach and small intestine and is labeled 'resistant starch' but this portion is difficult to measure and depends on a number of factors including the form of starch and the method of cooking prior to consumption. Resistant starch should be considered a dietary fiber and can be defined as the sum of starch and products of starch degradation not absorbed in the small intestine of healthy individuals. It serves as a primary source of substrate for intestinal microflora, which make important vitamins (and intestinal gas) and has several important physiological roles. Resistant starch has been categorized as physically inaccessible (RS1), raw ungelatinized starch (e.g. in banana; RS2), thermally stable retrograded starch (e.g. as found in bread, especially stale bread; RS3) and chemically modified starch (RS4). Many functional derivatives of starches are marketed including cross-linked, oxidized, acetylated, hydroxypropylated and partially hydrolyzed material.
For example, partially hydrolyzed (i.e., about two bonds hydrolyzed out of eleven) starch (dextrin) is used in sauces to control viscosity.