Analysis of pea lipid content by gas chromatographic and microgravimetric methods. genotype variation in lipid content and fatty acid composition

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Abstract
Two methods were developed for the analysis of total lipid content in dried peas. The first measured total fatty acid methyl esters (total FAME) by gas chromatography. The second was a microgravimetric method. Both methods gave equally precise results with a skilled analyst but the total FAME method required less sample, was easier to use and was preferred for the analysis of large numbers of samples. Using the total FAME method a wide range of pea genotypes including primitive or wild forms, field peas, and round and wrinkled garden peas were analysed. The lipid content, expressed as percentage by weight, of dry whole pea flours prepared from 166 genotypes ranged from 1.4–4.0% and exhibited a bimodal distribution. The lower lipid population corresponded to round peas and the higher lipid population to wrinkled peas. Although only five fatty acids occurred in significant quantities in the total lipid there was considerable variation in their individual contents. In decreasing order of content, in the vast majority of genotypes, the fatty acids were linoleic (18:2), oleic (18:1), palmitic (16:0), linolenic (18:3) and stearic (18:0). In a few genotypes, however, oleic acid predominated over linoleic acid. Linolenic acid ranged from 2.5–14.9% of the total fatty acids. A positive linear correlation (r=0.98) was found to exist between total FAME values (LF) and corresponding gravimetric lipid values (LG) for a combined population of round and wrinkled peas. An initial calibration was derived by regression analysis of data obtained by the FAME method and a large scale gravimetric method. This was tested and found to give satisfactory prediction of LG on a second set of samples analysed by the FAME method and the microgravimetric method.

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