THE SIGNIFICANCE OF STARCH POLYMORPHISM IN COMMERCIALLY PRODUCED PARBOILED RICE

A study of eight commercial parboiled samples derived from two varieti es of rice produced by four different processes has shown that dependi ng on the parboiling process, the starch component itself can be prese nt as native and/or retrograded starch in addition to the amylose-lipi d complex. Further, it was demonstrated that the polymorphic slates of starch can influence the texture and behaviour of cooked rice. The pa rboiled rice samples which had all three states of starch (i.e. ungela tinized and recrystallized amylopectin plus the amylose-lipid complex) possessed the hardest eating property but the lowest solubility. A ne gative linear relationship was demonstrated be tween the hardness and the solubility of cooked, parboiled rice. Overall, the observations su ggest the existence of different forms of starch in parboiled rice whi ch vary with the different parboiling protocols. The conditions govern ing their formation need to be established before investigating the sp ecific functionality of individual forms within the rice. This study f urther confirmed that retrograded starch (amylopectin) in parboiled ri ce did not exhibit a B-tye X-ray pattern but mixed A+V patterns.