Use of cyclodextrins as secondary antioxidants to improve the color of fresh pear juice.

In this paper, the color of fresh pear juice was evaluated for the first time in the presence of some natural and modified cyclodextrins (CDs) and the effect of these compounds as browning inhibitors was determined using the color space CIELAB system. Furthermore, because contradictory claims have been published concerning the mechanism by which enzymatic browning is inhibited by CDs, a kinetic model in the presence of CDs is proposed and the corresponding apparent complexation constants between the mixtures of diphenols present in pear juice and alpha-, beta-, and maltosyl-beta-CD have been calculated. Moreover, pear juice color was studied in the presence of different polyphenoloxidase inhibitors. Finally, we show that maltosyl-beta-CD enhances the ability of ascorbic acid to prevent enzymatic browning because of the protection that maltosyl-beta-CD offers against ascorbic acid oxidation. In this respect, maltosyl-beta-CD seems to act as a "secondary antioxidant", reducing pear juice browning and enhancing the naturally occurring antioxidant capacity of pear juice.