In Situ De‐esterification of lime pectin

Abstract

The in situ de-esterification of pectin in lime pulp by the action of pectinesterase (PE) has been investigated. It has been shown that the degree of pectin esterification is reduced to about 20% when the pulp is held at pH 8.5 for 90 min. The rate of de-esterification by the enzyme in situ is highest when the pH is in the range 7.5-9.0 and the NaCl concentration is 0.1-0.3111. At pH values above 9 chemical de-esterification becomes important. The activity of extracted lime PE was shown to be almost independent of pH in the range pH 6.c9.0. It is suggested that the difference between the behaviour of the extracted and the in situ enzyme is due to the fact that the latter needs to be solubilised before it can act on some of the pectin in the pulp. In support of this it is found that the proportion of lime PE which can be extracted from the pulp decreases with decreasing pH and ionic strength, reflecting electrostatic binding to the cell wall.

Solubilization of Cell Wall Bound, Thermostable Pectinesterase from Valencia Orange

“…An incremental increase in the pH of extraction did not greatly improve the efficiency of extraction and had a detrimental effect on enzyme recovety at pH 11.0. These results contrast with those of King et al (1986) who observed that an increase in pH from 3.5 to 8.5 to 10.0, at constant ionic strength of 0.3M NaCl, increased the percentage of PE solubilized from lime from 38% to 70% to 90%, respectively.…”

In‐situ pectin de‐esterification of alkali‐treated fruit waste materials

“…This was further substantiated by calculation of the levels of PE activity for the unripe and ripe peels assuming that only the soluble pectin was de-esterified and to the DE determined in the initial 5 min which were 11 and 13 units g-' DM respectively. These levels of activity were similar to those determined by titration with NaOH (King et al 1988).…”

“…The ripe and unripe fruits were processed to obtain pulp as described previously (King et al1986) and the freeze-dried material was stored at -15°C. The mangoes were classified according to their stage of ripeness as unripe, semi-ripe or ripe, and the peel was removed and dried as described previously (King et al 1988).…”

Rheo-NMR Studies of an Enzymatic Reaction: Evidence of a Shear-Stable Macromolecular System

“…Plant PMEs show optimal performance in the pH range of 6.5-9.5, whereas fungal PMEs show optimal performance under acidic conditions (pH 4.0-5.2) (28). It has been reported that PME does not act on a methylesterified component that is located between two deesterified carboxyl groups, and does not completely deesterify pectin, stopping at a certain degree of esterification governed presumably by the requirement of a particular binding epitope (34)(35)(36)(37)(38).…”