Dissolved pectins are decomposed spontaneously by
deesterification as well as by depolymerisation; the rate of this
decomposition depends on pH, on water activity, and on the
temperature. In general, maximum stability is found at pH 4. The presence of sugar in the pectin solution has a certain protective
effect while elevated temperatures increase the rate of degradation.
At low pH-values and elevated temperatures degradation due to
hydrolysis of glycosidic linkages is observed. Deesterification is also
favoured by low pH. By deesterification a HM-pectin becomes
slower setting or gradually adapts LM-pectin characteristics. At
near-to-neutral pH (5-6), HM-pectin is stable at room temperature
only. As the temperature (or pH) increases, a so-called âelimination
starts which results in chain cleavage and very rapid loss
of viscosity and gelling properties. LM-pectins show a somewhat
better stability at these conditions. At alkaline pH-values pectin is
rapidly deesterified and degraded even at room temperature (Rolin,
1993).