2005 Volume 49 Issue 1 Pages 24-29
A high level of ethanal (acetaldehyde) was generated from mackerel muscle homogenate by addition of potassium bromate (mild oxidizing agent) to the homogenate and heating. Lactic acid was found to be a causative substance of ethanal production (EP). However, such a high level of ethanal was not produced only by addition of potassium bromate to lactic acid in the reaction mixture and heating, suggesting the presence of unknown substances in mackerel muscle promoting the reaction of EP. In fractionation of a liquid extract of mackerel muscle on ion-exchange resin, the ampholytic substance fraction (ASF) showed a strong enhancing activity in EP from lactic acid. Sephadex G-10 gel chromatography of the ASF revealed that the amino acids-eluting fractions had an enhancing activity in EP and the substances enhancing EP were thought to be of relatively low molecular weights. In fractionation of the ASF on a SP-Sephadex C-25 cation exchange unit, the histidine-eluting fractions showed a strong enhancing activity in EP. When histidine was used instead of the ASF in reaction mixture, however, the enhancing activity of the former in EP from lactic acid was not so large as that of the latter. Iron-ion- and biological-iron-containing compounds, such as myoglobin, hemoglobin and cytochrome c, generated ethanal markedly from lactic acid. From the findings that the substances enhancing EP from lactic acid in mackerel extract had relatively low molecular weights and also from the behaviors on iron-exchange resin, it was considered that a complex of iron ions and histidine might play, at least in part, an important role in enhancing EP from lactic acid.
