Abstract: In order to realize high-value utilization of rice processing by-products, a method based on infrared radiation was developed to improve the antioxidant properties of rice bran polysaccharides. Under the condition of infrared radiation intensity of 2 780 W/m2, fresh rice bran was heated until the surface temperature reached 70, 75, 80, 85 and 90 ℃, separately. The effects of infrared radiation treatment on the extraction yield and composition of polysaccharides were analyzed by the sulfuric acid-phenol method and gas chromatography (GC), respectively. The in vitro antioxidant activity of the samples obtained was further studied and the effect of this treatment on the nutritional properties of rice bran polysaccharides was discussed. The results showed that when the surface temperature of rice bran was 75 ℃, the yield of polysaccharides reached its highest value, which was 18.33% higher than that of untreated control. In addition, the relative contents of rhamnose and mannose in the treated group were significantly increased, reaching their highest values at 80 and 85 ℃, respectively. The in vitro antioxidant results showed that the highest 1,1-diphenyl-2-trinitrophenylhydrazine (DPPH) radical scavenging activity of (25.21 ± 0.88)% was obtained at 85 ℃. The optimal temperatures for obtaining the highest hydroxyl (·OH) and superoxide anion (O2-·) radical scavenging activity of (61.24 ± 1.08)% and (35.93 ± 0.24)% were 80 and 75 ℃, respectively. In conclusion, infrared radiation treatment can help improve the extraction yield of rice bran polysaccharides and simultaneous maintain good antioxidant properties.

Key words: infrared radiation, rice bran, monosaccharide composition, gas chromatography, antioxidant activity