[Enzymatic breakdown of linoleic acid hydroperoxides to volatile carbonyl compounds by isomerase from barley (author's transl)].

Barley protein fractions with active isomerase, purified by means of gelchromatography were incubated at room temperature with linoleic acid hydroperoxides (LHPO), containing 9-hydroperoxy-10-trans,12-cis-octadecadienoic acid (9-LHPO) and 13-hydroperoxy-9-cis,11-trans-octadecadienoic acid (13-LHPO) in the ratio of about 1:1. The volatile compounds resulting from the reaction have been isolated, concentrated and investigated by means of gas- and radio-gaschromatography. In the case of incomplete LHPO-breakdown remaining hydroperoxides and nonvolatile breakdown products have been separated before gaschromatographic analysis. In addition to hexanal as main product, traces of 2-tr-heptenal and 2-tr-octenal were found; about 6% of the converted hydroperoxides were transformed to carbonyl compounds. By numerous additional experiments it was confirmed that the volatile compounds are formed by enzymatic catalysis.