CHARACTERIZATION AND OCCURRENCE OF LIPOXYGENASE IN BELL PEPPERS AT DIFFERENT RIPENING STAGES IN RELATION TO THE FORMATION OF VOLATILE FLAVOR COMPOUNDS

Extracts of green bell peppers (Capsicum annuum cv. Mazurka) were analyzed for the presence of lipoxygenase (LOX). A pH optimum of 5.5-6.0 was obtained, and enzyme activity was 100% and 51% inhibited by 10, mM n-propyl gallate and 340 mu M 5,8,11,14-eicosatetraynoic acid (ETYA), respectively. When bell peppers ripened from green to completely red, LOX activity decreased 70%. Also, the composition of volatile breakdown products from unsaturated fatty acids changed drastically upon maturation. Four typical patterns for these volatile products could be distinguished during ripening; some changed similarly to LOX activity. In both green and red bell pepper homogenates, the addition of linoleic acid increased considerably the levels of hexanal and hexanol, whereas the levels of (Z)-3-hexenal and (E)-2-hexenal were markedly enhanced by the addition of linolenic acid. When ETYA was added to these systems, the enhancing effects of both substrates were drastically reduced. A biochemical pathway was proposed for the formation of volatile bell pepper compounds upon tissue disruption.