Resistant Wheat Starch
Resistant wheat starch is an amylase-resistant starch from wheat belonging to RS4-type classification. It is manufactured by modifying wheat starch with a combination of sodium trimetaphosphate and sodium tripolyphosphate present in an approximate weight ratio of 99:1 and at suitable reaction conditions of time, temperature and pH and in the presence of salt (sodium sulfate). The reaction involves the introduction of numerous phosphate cross-linking bonds with proportionately lower level of substituting phosphate bonds. As a result, the Resistant wheat starch has restricted swelling even after cooking or heat treatment. Analysis by AOAC Method 991.43 gives at least 85 percent total dietary fiber (dry basis). The mechanism of resistance to enzyme digestion may be explained by the markedly reduced ability to form enzyme-starch complex due to steric hindrance by phosphate groups. Resistant wheat starch is primarily used in foods for fiber fortification and caloric reduction.