Evaluation of the Effect lf Ozone Gas on Quality Characteristics of Rice Grain (Var. Fajr)

Rice (Oryza sativa L.) is the second most important cereal after the wheat crop in the world. Rice grains and their products make up about 40% of the food needed by half of the world population. To replace new and low-risk methods in grain storage while maintaining its quality, in this study, the effects of ozone gas concentration and exposure time after a four-months storage period on some characteristics of Fajr Var. rice including cooking time, loss of solids, Water absorption, amylose content, the weight of cooked rice, cooked grain elongation ratio, gelatinization score and volumetric expansion) using a completely randomized design in (4×4) factorial experiments with four levels of ozone concentration (i.e. 0, 25, 50 and 75 ppm) and four levels of exposure time (i.e. 1, 3, 5 and 7 days) with three replications were examined. The results showed that the ozone gas concentration had a significant effect at the (P<0.01) on all cooking characteristics of rice grain except volumetric expansion, cooked grain elongation, cooking time, gelatinization score and amylose content. The maximum weight of rice cooked (13.12 g), water absorption (8.12 g), loss of solids (0.59 g), cooked grain elongation (1.428) with a significant difference (P <0.05) occurred at concentrations of 0, 25, 50 and 75 ppm, respectively. In addition, there was no significant difference (P <0.05) for the cooking time (11.71 min), gelatinization score (2.63) and amylose content (23.24%) with the ozone concentrations (50, 75 and 25 ppm), respectively. The volumetric expansion characteristics (P<0.05), the content of solids and the amount of amylose (P <0.01) were significantly affected by the duration of treatment, so that the maximum volumetric expansion (4.16), weight loss of solids (0.613 g), and the rate of amylose (24.80%) were observed at 1, 3 and 1 day, respectively. Therefore, regarding the interaction between ozone gas concentration and exposure time, it was recommended to the storage of rice grain ozonation with 25 ppm for five days must be used because of having a maximum weight of boiled rice (11.51 gr) and water absorption (10.11 gr) with significant differences (p< 0.01), and no significant effects (p< 0.01) on the other characteristics.