Gas-chromatographic Determination of Esterified and Free Organic Acids in Various Kinds of "Miso"

Abstract

In the previous paper we presented a rapid and exact method (an alkaline method) to extract ethylester of fatty acids and glycerides as well as free organic acids in "miso". Employing the method twenty kinds of miso including rice koji, soybean koji, barley koji and local home made "miso" were analyzed by gas chromatography and following results were obtained. (1) The amount of ethylester of fatty acids showed about double of the values reported previously by the celite method, and nearly 50% of the total fatty acids in the original glycerides exsisted as their ethyl esters in "miso". (2) Free organic and fatty acids in various kinds of "miso" were found generally lower than 0.75%, and the dominant acids in non-volatile was lactic acid. The content of free fattyacids in soybean koji "miso" was near 0.18% which was higher than the average content of rice koji "miso" (0.01%). (3) From a kind of soybean koji miso in Aichi Prefecture, a mixture of ethylesters and methylesters of fatty acids was found in about equal amounts. (4) Concerning volatile organic acids, acetic, isobutyric and iso-valeric acids were found in all of the tested "miso". The later two acids giving uncomfortable flavor to miso were found higher in home soybean and rice koji miso (0.014%) than commercial rice koji "miso".