Hydroperoxide lyase activity was found in sugar beet leaves. Its optimum pH and temperature were, respectively, 6.7 and 22 degrees C. Under these conditions, conversion of linolenic acid 13- hydroperoxide to cis- 3- hexenal with a maximum yield of 80% was reached after only 2 min. The stability of cis- 3- hexenal was improved by acidifying the reaction medium. Based on these studies, a bioprocess producing greennote aldehydes in a laboratory- scale was achieved.