Whole wheat flours were prepared by hammer mill (HM), stone mill (SM) and ultra-fine mill (UM) processes, during which entire wheat grain was ground by a hammer mill (Penten 3100, Sweden), an electric stone mill (custom-tailor) and an FDV ultra-fine mill (Beijing Kingslh Instruments Ltd., Beijing, CN), respectively. Whole wheat flours collected from above processes were all passed though a CQ20 screen before use