Proximate composition, calorie content and heavy metals (As, Cd, Pb) of selected Sri Lankan traditional rice (Oryza sativa L.) varieties

Abstract

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There are over 2000 Sri Lankan traditional rice varieties (STRV) known to have existed in Sri Lanka. But only about 30 varieties have been subjected to scientific research and proven to have high nutritional and medicinal properties. Therefore, uncovering the nutritional values of the rest of the STRV has become very important. Standard methods of AOAC nutritional guidelines were used to obtain the proximate composition of six STRV; Kalu heenati (KH), Pokkali (PK), Gurusinghe wee (GW), Kahawanu (KW), Sudu murunga (SM) and Unakola samba (US). Heavy metals (As, Cd and Pb) of these STRV were determined by using an ICP-AES. The moisture content of selected STRV ranged from 11.2±0.2 % -11.9± 0.2 %. The results showed that crude protein content of the selected STRV was in the range of 9.7±0.3 % - 11.0±0.4 % KH had the highest crude protein content while SM had the least. In relation to crude fiber content, SM had the highest percentage (1.14±0.04 %), while the lowest (0.92±0.03 %) was recorded for KH. Crude fat content of all the STRV ranged from 2.3±0.0 % - 2.9±0.1 %. US had the highest crude fat content while PK and GW similarly had the least. PK had the highest ash content of 1.9±0.1 % and the least ash content of 1.2±0.0 % was shown by SM. Carbohydrate content of the selected STRV ranged from 72.0±0.1 % - 76.3±0.1 %. Calorie contents of the selected STRV were in the range of 352.3-372.8 Kcal/100 g and the highest value was reported for KH. The study reveals that the levels of As, Cd and Pb were below the limit of quantification (LOQ: Pb-0.04 ppm, As-0.02 ppm and Cd-0.01 ppm). Therefore, consumption of STRV may not cause metal toxicity due to Pb, Cd or As. This reveals that STRV show high nutritional values than those values reported for the improved rice.