Investigation of changes in chemical composition and rheological properties of Kyrgyz rice cultivars (Ozgon rice) depending on long-term stack-storage after harvesting

The present work investigated the effect of long-term stack-storage after harvesting on selected chemical and rheological properties of Kyrgyz rice cultivars, Ozgon. The performance indicators of in stack-stored Ozgon rice samples after 4, 6, and 12 days was grain size, grain weight, color, moisture, total starch, amylose, protein, fat and ash contents, and mineral composition as well as the rheological properties of rice flour dough. The change of stored rice is caused by the organic modification of the starch structure, decreasing of moisture as well as proteolysis of proteins in the endosperm. The increase of fat and ash contents, mineral composition, and bio-functional components such as γ-oryzanol indicated the diffusion of micro- and macronutrients from rice bran into the rice endosperm and, thus improvement of the nutritional value of the rice flour. These changes in chemical composition directly influence the physical properties, such as pasting and viscoelastic properties of the rice flour dough as well as the browning of the rice grain.