Factors affecting gelation of high-ester citrus pectin

A study was made of the effect of sugar concentration on optimum pH and jelly strength of high-ester citrus pectin jellies. The effect of the degree of esterification of pectin, concentration of ash constituents and jelly pH on the grade, setting temperature and setting time of sugar acid pectin jellies was also investigated. With jellies containing 55-65% sugar, wide variations in acidity beyond a certain minimum value have little or no effect on jelly strength. The effect of acid beyond the optimum appears to be that of materially increasing the rate of jelly formation. This rate may be reduced by lowering the sugar concentration so that no drop beyond the optimum occurs. The influence of the degree of esterification has been studied using pectins with different degrees of esterification prepared by saponification in an acid environment. The jellying power of partially saponified pectins is considerably more than the jellying power of pectins with a higher degree of esterification from which they were prepared. The setting time of jellies containing a pectin with a low ash content increased with a decreased degree of esterification of pectins to about 50%, while jellies from pectins with lower degrees of esterification exhibited shorter setting times. The addition of calcium to jellies caused an increase in setting temperatures in all cases, but this effect was much stronger when the pectins had lower degrees of esterification. Therefore, pectins with a degree of esterification of about 45-55% can be used as rapid-set pectins. (C) 1997 Elsevier Science Ltd.