みそのエステル型脂肪酸,遊離脂肪酸および有機酸の抽出とガスクロマトグラフィーみそ成分の研究(第1報)

概要

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A modified method for efficient extraction of lipids from miso and for successive determination of ethyl esters, total glycerides and free organic acids was developed. By this method, glycerides and ethyl esters of fatty acids were extracted with diethyl ether after adjusting the pH of the miso cake emulsion to 12.0 with 0.02N sodium hydroxide solution. In the conventional celite method, the miso emulsion is filtered on celite and the residue is extracted with diethyl ether. Ethyl esters of fatty acids were determined by direct GC analysis of the first ether extract from the alkaline miso emulsion using DEGS columns. The amount of total glycerides is shown by subtracting the ethylesters of fatty acids from the value obtained by transesterification with BF3-methanol of the first ether extract of miso. On the other hand, the aqueous layer separated from the first ether extract was acidified to pH 2.0 and then extracted with diethyl ether continuously for 4 days. The resulting acids in the second extract were methylated with diazomethane to determine the amounts of free fatty acids and various non-volatile organic acids. The yield of the first ether extract obtained by our method was about 2-times higher than that by the celite filtration method. The present procedure provides a rapid and reliable method for fractional determination of miso fatty and organic acids as ethyl ester, glycerides and in free forms.
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