A study of factors affecting in-situ de-esterification of mango (Mangifera indica) pectin.
King K., Norton G., Mitchell J. R., Caygill J.
Author Affiliation: Dep. Appl. Biochem. & Fd. Sci., Univ. Nottingham Sch. Agric., Sutton Bonnington, Loughborough LE12 5RD, UK.
Journal of the Science of Food and Agriculture 45 : 231-241
Abstract : De-esterification of mango peel pectin in situ by the action of the enzyme pectinesterase (PE) was investigated. The rate of enzymic de-esterification was highest between pH 8.5 and 9.5 with chemical de-esterification also being important. In situ PE activity declined with fruit ripening but remained relatively constant when assayed on citrus pectin. The most likely explanation for this difference is a change in suitability of the pectin substrate within the fruit during ripening. A reduction in the degree of esterification (DE) of the pectin to 36-42% was obtained following incubation of the mango peels at pH 8.5 for 90 min. A crude preparation of exogenous PE from mango peel and lime pulp was incubated at pH 8.5 with heat-treated (PE-inactive) peel as a means of increasing the rate and extent of de-esterification. The PE activity of both these exogenous enzyme preparations was lower on the peel than that of the in situ mango enzyme, but considerably higher on a hot-water-soluble fraction extracted from the peel. It is suggested that enzyme solubiliy and pectin accessibility are the major factors affecting in situ de-esterification of pectin in mango peel.