Fatty acid, tocopherol and sterol composition as well as oxidative stability of three unusual sudanese oils

Abstract

Three unusual oils, obtained from Sclerocarya birrea (Marula), Aspongopus viduatus (melon bug) and Agonoscelis pubescens (sorghum bug), collected in Sudan from Abu Gibaiha, Ghibaish and Rahad agricultural areas, respectively, were investigated. In addition to the oil content, the fatty acid as well as sterol composition was determined by capillary gas chromatography and the tocopherols were evaluated by high-performance liquid chromatography. Oxidative stability of the oils was investigated by the Rancimat method. The oil content of seeds from S. birrea amounted to 53.5%, whereas bugs of A. viduatus and A. pubescens came to 45 and 60%, respectively. The oils contained 67.2, 46.5 and 40.9% oleic acid, 5.9, 3.4 and 34.5% linoleic acid, 14.1, 44.2 and 12.1% palmitic acid and traces of linolenic acid, respectively. The tocopherol content of these oils amounted to 13.7, 0.3 and 34.0mg/100g oil, respectively. Gammatocopherol was the predominant tocopherol in the oil of S. birrea and A. pubescens. The total content of sterols in the three oils was 287, 17 and 450mg/100g oil, respectively, whereas β-sitosterol was determined as the main compound in all oils with about 60% of the total sterols. In the oil of S. birrea higher amounts of 5-avenasterol (4.8mg/100g) were found. The oxidative stability of the oils, as measured by the Rancimat test at 120C, was 43, 38 and 5.1 h, respectively. © Copyright 2004, Blackwell Publishing All Rights Reserved.