Extraction and Characterization of Native Starch From Black and Red Rice

The objective of the study is to extract and characterize red rice starch, a grain commonly consumed in the Northeast region of Brazil and to compare it with the starch obtained from black rice, widely spread in eastern countries. Starch was extracted by immersion of rice in sodium metabisulfite (0.2%), followed by milling, filtration, decantation and drying at 50 °C. The obtained starches were characterized by the following parameters- physicochemical, physical, rheological, textural, structural, thermal and morphological. The highest starch extraction yield was found in red rice grains (67.84%), where it obtained higher water absorption and lower apparent viscosity, firmness and gum. Both starch gels indicate the behavior of non-Newtonian fluid in the specific case of pseudoplastic crystallinity type A and with polyhedral geometry. For the thermal analysis of red rice starch, it was observed higher gelatinization temperature and lower gelatinization enthalpy. Black and red rice grains can be considered an alternative source of starch, especially red rice, which has a lower cost due to its production in the country.