Milling and roasting impact pasting and rheological properties of oat flours and quality of steamed oat cakes.

Roasting is the traditional heat treatment of oat kernels before milling in China. The effects of roasting and milling methods on the physicochemical properties of oat flour and the quality of the steamed oat cake have not been explored. Roasting treatment caused a looser structure of the oat grain, which made the oat grain easier to crush. Stone milling induced severe damage (92 g/kg) and aggregation of starch granules, resulting in the highest total starch hydrolysis rate of oat flour and the highest total gas volume of raw oat batter. However, the pore expansion capacity was restricted, resulting in the minimum specific volume and the highest hardness of steamed oat cake. Ultrafine milling produced a more uniformly particle size distribution of raw and roasted oat flour and the steamed oat cake prepared with ultrafine-milled raw oat flour had the maximum specific volume and minimum hardness, 2.75 mL/g and 6.01 N. Pulverizer milling resulted in the lowest solubility index and the lowest starch hydrolysis rate of raw and roasted oat flour. Raw whole oat flour prepared by ultrafine milling or pulverizer milling gave softer steamed oat cakes with higher volume or slower starch degradation, respectively. • Stone milling induced severe damage and aggregation of starch granules. • Pulverizer milling led to the lowest solubility index and starch hydrolysis rate. • Steamed oat cake made of ultrafine-milled raw flour had the maximum specific volume. • Roasting reduced gas production capacity and resulted in uneven gas chamber structure. • Raw oat flour prepared by ultrafine milling is more suitable for making steamed oat cake. [ABSTRACT FROM AUTHOR]