Physicochemical Properties of the Rice Flour and Structural Features of the Isolated Starches from Saline-Tolerant Rice Grown at Different Levels of Soil Salinity

Three varieties of saline-tolerant indica rice were grown in soils with salinities of 0.0–0.6% (w/w). The rice grown at salinities of 0.3 and 0.6% had a smaller grain dimension than its counterpart. Salinity stress altered the physiology of plants, leading to changes in the basic chemical compositions for all rice varieties, e.g., increasing the soil salinity improved the content of rice protein (RP). The pasting and rheological properties of the rice flour highly depended on its chemical compositions. An increase of RP inhibited the swelling of starch granules and accordingly decreased the peak viscosity of rice flour, while the aggregation of RP weakened the gel structure of the cooked rice flour. The isolated starches showed polyhedral granules, and they all had an A-type crystalline structure with relative crystallinity varying from 34.16 to 45.40%. Moreover, increasing the soil salinity enhanced the lamellar order and periodic length of the isolated starches.