Effect of pepper lipoxygenase activity and its linked reactions on pigments of the pepper fruit

The products formed during the enzymatic reaction catalyzed by the lipoxyge nase of pepper (variety Agridulce) have in vitro a strong destructive actio n on the carotenoid pigments of the fruit. When conditions and proportions of enzyme and pigments are similar to those found in the fruit, and at a re action temperature of 20 degrees C, almost 30% of the pigments are destroye d after 24 h of reaction. Of this amount, 2.5% is due to autoxidation of pi gments, 4.5% to oxidation induced by the presence of linoleic under saturat ing conditions, and the remaining 22% to the presence in the medium of reac tion products of the lipoxygenase-catalyzed reaction. When the enzyme acts under substrate-saturating conditions, the rate of pigment destruction by l ipoxygenase can be considered maximal at the experimental temperature. The fact that in vitro pepper lipoxygenase induces a heavy destruction of pigme nts and that, in vivo, its activity remains almost, constant during over-ri pening could explain why up to 40% of the pigment content in some varieties is lost during the postharvest period.