Parboiling : a process that deeply changes the properties of rice Thermoanalytical Approach

DSC, TGA and Texture Analysis (with Kramer Cell) investigations allowed a thorough comparison between parboiled and white rice from RIBE cultivar cooked in excess water to various extent. Parboiling implies a complete gelatinization of the rice starch and the formation of a homogeneous structure of the kernels; the cooking process corresponds to the migration of water from the surface toward the core through a practically isotropic mean. Cooking of white rice instead implies the progress of starch gelatinization from the surface toward the core which therefore produces a layered kernel structure in the partially cooked rice. As a result the final texture of the cooked rice is significantly different in the two cases. In the case of parboiled rice, a straight line correlation was found between the chewing load (simulated with dynamometric tests) and the water content of the material, no matter the temperature-time operative conditions selected for the parboiling process. This finding can have a practical applications as far as it suggests that the mechanical (and other) properties of the parboiled rice can be tuned through the control of the water uptake on cooking. This is not the case of white rice.