Non-starch lipids and starch lipids in milled rice

Abstract

Milled white rice was reduced to a fine flour for lipid extraction. Quantitative recoveries of non-starch lipids completely free from starch lipids could not be obtained. Total lipids were extracted from rice flour, therefore, and starch lipids from purified starch; the composition of the non-starch lipids could then be obtained by difference. The non-waxy starches (12·2–28·6%, w/w, amylose) contained 0·9–1·3% (w/w) lipids comprising 29–45% fatty acids and 48–67% lysophospholipids, whereas the waxy starches (1·0–2·3% amylose) contained negligible amounts of lipids. The total lipid content of the rice flours ranged from 0·89 to 2·16%. The non-starch lipids in the waxy rice varieties consisted of triacylglycerols, fatty acids, small amounts of other non-polar lipids, glycolipids and phospholipids. Calculations showed that the non-starch lipids in the non-waxy varieties were similar; all samples showed evidence of partial lipolysis of the full acylated non-starch lipids usually found in endosperm tissue of cereal grains. Considerable variation in the quantities of total lipids and starch lipids were found in two rice varieties grown at nine locations throughout Europe, the Middle East and N. Africa.