Proximate Composition, Mineral Composition and Phytic Acid in Three Common Malawian White Rice Grains

Abstract

Rice is the second most important food crop in Malawi, after maize. Some studies have reported on losses of macro- and micronutrients in rice grains subjected to different polishing rates. In this study, the proximate composition, mineral contents and phytic acid profile of three white (i.e. polished) rice varieties in Malawi were investigated. Proximate composition was determined by adopting AOAC method. Mineral contents were determined using flame atomic absorption spectrophotometer and phytic acid determined using standard procedures. The results show that proximate composition for the three varieties were variable in the with ranges being 9.35-10.42%, 0.69-0.90%, 5.43-7.03%, 0.72-1.71%, 1.42-3.15%, 81.41-82.45% and 39.56-42.10%, for moisture, ash, crude protein, crude fat, crude fibre, carbohydrate and energy content, respectively. Significant amounts of minerals were present in all three rice varieties in the ranges: 5.19-7.81 mg/100g for calcium; 30.21-40.32 mg/100g for magnesium; 216-268 mg/100g for potassium; 0.33-0.58 mg/100g for manganese; 0.77-1.40 mg/100g for zinc; 0.26-0.47 mg/100g for copper; and .83-2.49 mg/100g for iron. Phytic acid ranged between 93.10 and 204.92 mg/100g in all the three rice varieties, whereas heavy metals such as lead, chromium and cadmium were not detected in all varieties. The results suggest that the white rice varieties could serve as an alternative source of food for humans and animals after quality processing.

Keywords: Malawian White Rice Grains, Proximate Composition, Minerals, Nutrient Content, Phytic Acid.