Quantitative changes in guava polyphenols and the polyphenoloxidase (PPO) at different stages of maturation, ripening and storage.

The total polyphenols decreased in all stages of maturation, and ripening, whereas, the non-tannin phenolics contents were higher than the tannin phenolics in both white and pink varieties of guava and also the decreasing rate of non-tannin phenolics was much less than that of the tannin phenolics, although in both cases the non-tannin phenolics and the tannin phenolics were found to be decreased. The polyphenolic fractions, such as, simple polyphenols, hydrolysable tannins, non-tannin flavans and condensed tannins were found to be at a decreasing trend with maturation and ripening, although the content of hydrolysable tannins and non-tannin flavans was found to be small in quantity and the simple polyphenols constitute the major portion of the phenolics in the methanolic extract. The degree of polymerization of the methanolic extract was studied. The insoluble leucoanthocyanins were found to be the major component of the whole guava polyphenolics. There was no significant amount of polyphenoloxidase activity in immature and mature guava, but, at ripening the activity was noticeable. The activity was found to be increased remarkably at full ripening in both the varities.