Mechanisms of starch gelatinization during heating of wheat flour and its effect on in vitro starch digestibility

Abstract

This study aimed to understand mechanisms of starch gelatinization during heating of wheat (Triticum aestivum L.) flour, and its effects on in vitro starch amylolysis of cooked wheat flour. At water content of 20%, cooking did not disrupt greatly the crystalline structures of starch in wheat flour. Considerable disruption of ordered structures of starch occurred with cooking at a water content of 30%, and starch was fully gelatinized at a water content of 40%. The transition of the X-ray diffraction pattern from A to V types with increasing water content suggested the formation of starch-lipid complexes during cooking of flour. Typical starch pasting profiles of cooked wheat flour were observed at water contents of 40 and 50%, whereas longer cooking time decreased the pasting viscosities of the flour. Cooking the flour for only 5 min with 20% water greatly increased the rate and extent of in vitro enzymatic digestion of starch, which were not increased further by longer cooking or higher water content. From this study, we conclude that the progression of starch gelatinization during cooking was not greatly affected by non-starch components in wheat flour, and that some structural order in amorphous regions of starch contributed to the development of pasting viscosities.