Abstract
Methods are described for the extraction and quantification of total lipids in cereal grains and other similar tissues, and for the determination of all the major classes of acyl lipid found in these extracts. Total lipids, obtained by direct solvent extraction or after acid hydrolysis, are quantified as fatty acid methyl esters (FAME) by gas chromatography (g.c.), using heptadecanoate (17:0) as internal standard. Individual lipid classes are separated by thinβlayer chromatography; nonβpolar lipids and glycolipids are measured as FAME by g.c., while phospholipids are determined from phosphorus distribution. Crude lipid extracts are used to avoid losses during purification, and methanolysis of lipid classes is always performed without extracting the lipids from silica gel in order to minimise autoxidation, handling losses and contamination. Corrections are described for minor losses during experimental procedures, and factors are given for conversion of weights of FAME or phosphorus into weights of original lipid. In the authors' laboratory the precision of routine determinations (variations expressed as percentage of mean values) are usually well within the limits: total lipids, 1.5%; major lipid classes, 1.5%; minor lipid classes, 5%.