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Abstract

Rice (Oryza sativa) is a pivotal staple food providing important contribution to the calorie intake for a large number of world population. Furthermore, rice contains melatonin that is favourable for human health. However, the nutritional properties of rice including melatonin differ in specific classified rice varieties. Additionally, changes in the chemical compositions of rice can also occur during the cooking processes. Hence, the aim of the study described here was to screen a wide range of rice varieties in order to develop melatonin-rich rice products. Afterwards, to evaluate the profile of melatonin during the cooking processes including soaking, boiling and warming. The levels of melatonin on the tested rice samples were decreased up to 80% in average during the course of rice cooking. However, the final levels of cooked rice from melatonin-rich (whole grain) rice were remained high, especially pigmented rice (138 µg Kg-1 in red rice and 95 µg Kg-1 in black rice) which were significantly higher than the regular (6 µg Kg-1 in white polished grain) rice. Hence, these rice varieties could be chosen instead of the regular ones by the population interested in the properties associated to melatonin, without dramatic changes in their regular diets.