Impact of dry- and hydro-thermal treatments on swelling power, water absorption and water solubility on red-rice flours

The impact of dry- and hydro-thermal treatments on swelling power (SP), water absorption (WA) and water solubility (WS) of red-rice flour (RRF) were investigated. The dry-thermal treatment was conducted at RRF’s moisture content (mc) of 10%, and the hydro-thermal treatment was performed at the mc of 25%. There were two heating methods applied on RRF: oven (80oC) and autoclave (121oC) heating. The exposure duration was 8, 10 and 12 hours in an oven-heating; 15 and 30 minutes in an autoclave-heating. Results showed that exposure durations, moisture content and theirs interaction had significant effect on SP and WS of RRF for the autoclave-heating. WA and WS increased with longer exposure duration to heat, and at a higher heating temperature. WA of RRF (40.34%) at 8 hr of exposure duration increased to 51.43% after 12 hr of exposure duration (for dry-thermal treatment) and 45.36% to 50.76% for hydro-thermal treatment. Modification of RRF by hydro-thermal treatment in an autoclave gave better physical properties than that of heating in an oven with higher values on SP and WA, and lower value of W