A process for preventing enzymatic degradation of rutin in tartary buckwheat (Fagopyrum tataricum Gaertn) flour

The use of tartary buckwheat flour as a source of dietary rutin has been limited because of the enzymatic degradation of rutin during the dough-making process, which results in a bitter taste. A variety of pretreatment regimes, including heating, steaming, boiling, and extruding, were evaluated in relation to the inactivation of the rutin-degrading enzyme responsible for rutin loss and color change during dough-making. Steaming (120 sec), boiling (90 sec) buckwheat grains, or extruding (180 rpm/min at 140 degrees C) the flour resulted in the retention of >85% of the original rutin and eliminated the bitter taste in the hydrated flours. In contrast, dry heating at 140 degrees C for 9 min or microwaving at 2,450 MHz for 3 min did not reduce the rutin loss, and the bitter taste remained. Unlike in the flour, the rutin degradation in water-soaked grains was insignificant at room temperature. Moreover, the samples treated by steaming, boiling, or extrusion were darker and more reddish in color.