Abstract: Broken rice and flour from the whitening and polishing of brown rice was extruded, and main factors that affect the contents of soluble solids and soluble sugar in extruded rice flour were investigated. The results indicated that moisture content was the most significant affecting factor, followed by screw speed and extrusion temperature. The optimal moisture content, screw speed and extrusion temperature were determined as 25%, 240 r/min and 140 ℃, respectively. Under the optimal extrusion conditions, the contents of soluble solids and soluble sugar in extruded rice flour were 39.88% and 7.90%, respectively, revealing a 1.53- and 3.64-fold increase compared with those of non-extruded samples. HPLC analysis of soluble sugars in extruded rice flour obtained under the optimal conditions showed that 100 g of samples contained 275.124 mg of fructose, 891.632 mg of glucose, 853.144 mg of sucrose, 516.576 mg of maltose and 353.266 mg of maltotriose.

Key words: extrusion, rice flour, soluble solids, soluble sugars