Influence of developmental stage, cultivar, and hexapeptide and cyclodextrin inhibitors on polyphenol oxidase activity from tomato fruits

Two PPO preparations, one soluble and one particulate, were monitored at eight different developmental stages after anthesis of tomato fruits. Both PPO preparations showed significant decline after the 12th day postanthesis of fruit development. Although present in every cultivar tested, the two PPO preparations varied greatly in activity among the cultivars. The addition of 1-mM synthetic hexapeptides caused inhibition over 10% on PPO activity measured in both preparations. The antibrowning effect of the β-CD Cavasol W7M on PPO activity was also evaluated. Although the two families of compounds that we describe here, hexapeptides and CDs, react in very different ways either by physically blocking the active site of PPO or, alternatively, by chelating PPO substrates, they are common antibrowning compounds that can be commercially synthesized. These inhibitors are peptides and sugars, which are not likely to cause adverse health effects.