EFFECT OF γ-IRRADIATION ON PHYSICAL, FUNCTIONAL AND PASTING PROPERTIES OF FIVE RICE CULTIVARS

ABSTRACT

Irradiation is a processing technology for improving the safety and quality by extending the shelf-life of food products. Effect of γ-irradiation (2, 4, 6, 8 and 10 kGy) on color, functional and pasting properties of flours and starches of five cultivars of rice was investigated. Color (L, a, and b) of non- and γ-irradiated rice cultivars was measured, and the deltachroma (DC), color difference (DE) and hue angle were calculated. Functional and physicochemical (pasting) of the milled rice were determined using standards methods and rapid visco-analyzer, respectively. Generally, L, a, and b values of rice flour and starch were significantly (p ≤ 0.05) affected by irradiation dose. Calculated chroma, color intensity and hue angle varied with cultivar and γ-irradiation dose. Water Absorption Capacity of non irradiated and g-irradiated rice flour ranged from 6.24 (Faro 35) to 10.60 %/ (Faro 44) and 4.95 (Faro 55) to 14.4 % (Faro 44) respectively, while the Oil Absorption Capacity of non irradiated and g-irradiated rice flour ranged from 3.26 (Faro 44) to 4.23 % (Faro 55) and 3.17 (Faro 56) to 6.5 % (Faro 55) respectively. Oil absorption capacity of rice flour increased at higher g-irradiation dose respectively. Non irradiated rice (flour and starch) showed higher pasting properties (peak, trough, breakdown, final and setback viscosities) than the irradiated rice. Aside from breakdown viscosity, the pasting properties decreased significantly (p < 0.05) with increased γ-irradiation dose.

Keywords: Gamma irradiation; Rice (Oryza glaberriumn.); Starch; Pasting properties; Functional properties