Abstract:To develop an oat product with a low glycemic index（GI），oat dietary fiber powder was prepared using oats as the main raw material through processes including defatting，maturing，and ultrafine grinding.With fat residue rate as the evaluation index，the optimal defatting process conditions of the oat dietary fiber powder were determined by single-factor experiments and orthogonal experimental design.The effect of the defatting process on the color，particle size，and in vitro digestibility of the oat dietary fiber powder was investigated，and the GI value of the defatted oat dietary fiber powder was determined.The results showed that the optimal process conditions for fat removal from oat dietary fiber powder using n-butane were five extraction times，40 minutes of extraction，and a material-to-liquid ratio of 1∶1.0（g/mL）.Under these conditions，the fat residue rate of the oat dietary fiber powder was 0.20%.After the defatting process，the fat content of the oat dietary fiber powder decreased by 97%.The L* and a* values decreased，while the b* value increased.The particle size shifted toward a smaller range，and the median diameter（D0.5）decreased from 69.91 μm to 32.12 μm.The in vitro hydrolysis rate decreased from 56.64% to 40.33%.The GI test results showed that the GI value of the defatted oat dietary fiber powder was 36，indicating that it is a low-GI food.In conclusion，oat dietary fiber powder with low GI can be prepared through a defatting process，which can provide more dietary choices for people with chronic diseases such as diabetes and obesity.