Apples, pectin-esterases

Versteeg et al. (50) have isolated various multiple forms of pectin esterases in oranges and shown that they differ in affinity to pectins and pectates and in heat stability and therefore may play different roles in cloud loss phenomena. One form (about 5% of the total PE activity) was found to be much more heat stable than the other forms it was also active at low pH (2.5) and at low temperatures. Another form did not cause self-clarification for this enzyme a similar mode of attack was proposed as for fungal pectin esterases which produce low-ester pectins less sensitive to calcium. Multiple forms of pectin esterases are present in the fruits of all of the orange varieties and citrus species tested. The two isoenzymes known to be responsible for cloud loss and gelation in citrus products were found to occur in all of the component parts of the orange fruit (51). In the French cider industry the endogenous PE of apple is used for the self-clarification of apple juice (52). 

Native pectin esterases can be used for protecting and improving the texture and firmness of several processed fruits and vegetables these include apple slices (53), canned tomatoes (54), cauliflower (55), carrots (56), potatoes (56), beans (57) and peas (91). 

Cell wall pectin can be effectively solubilized and degraded by the combined action of pectin esterase and polygalacturonase as was demonstrated for apple and apricot tissue (86). 

Joshi, V. K., Parmar, M., and Rana, N. S. (2006). Pectin esterase production from apple pomace in solid-state and submerged fermentations. Food Technol. Biotechnol. 44,253-256. 

Klein, J. D., Hanzon, J., Irwin, P. L., Shalom, N. B., and Lurie, S. (1995). Pectin esterase activity and pectin methyl esterification in heated Golden Delicious apples. Phytochemistry 39, 491-494. 

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