Effect of parboiling on toxic metal content and nutritional composition of three rice varieties locally produced in Nigeria

Parboiling of rice is a common cooking method and its effect on quality of rice is sparse in the existing literature. The current study was designed to evaluate the effect of parboiling on levels of nutritional components and toxic metals of rice locally produced and consumed in Nigeria. Three varieties of rice were considered and each sample divided into two portions for parboiling and conventional cooking procedures using standard methods. The rice flours were prepared for proximate analysis, amino acid and vitamin profiles using HPLC, while minerals and toxic metals were analyzed by inductively-coupled plasma optical emission spectrometry (ICP-OES). Parboiling significantly (p<0.05) increased ash and fiber contents of the rice samples, whereas, lipids considerably (p<0.05) reduced compared to the unparboiled rice. The levels of some of the essential amino acids, vitamins were significantly reduced by parboiling. Parboiling markedly (p<0.05) reduced levels of aluminium, nickel, chromium and manganese; cadmium, lead and arsenic levels were however increased significantly by parboiling. This study reveals that parboiling may significantly affect components of cooked rice and exert impact that may alter health status. Future studies are suggested to clarify further the effect of parboiling on toxic metals in staple food like rice. (C) 2020 The Author(s). Published by Elsevier B.V. on behalf of African Institute of Mathematical Sciences / Next Einstein Initiative.