Freeze stability of starch mixtures. Interest of konjac glucomannan in reducing the freezable water and impact on gelatinization properties of potato starch.

Abstract

Konjac glucomannan (KGM) is a very attractive hydrocolloid with a very high water holding capacity. It is put to the fore by the media and attracts a lot of interest for specific applications such as gelling of liquids for elderly (dysphagia problems), ability to enhance satiety (diet applications), and others. Konjac glucomannan (KGM) could be a useful ingredient in increasing water holding capacity of starch gels and might affect the starch gelatinization. The objective of this study is to characterize the ability of blends of starch and KGM to reduce the amount of freezable water and to observe the influence of addition of this hydrocolloid on the gelatinization properties of potato starch. The effects of KGM on the gelatinization properties of potato starches were investigated by DSC showing that the addition of 1% (w/w) KGM in starch suspensions causes a decrease in the amount of available water. This appeared sufficient to disrupt the gelatinization of potato starch; in turn a higher stability of starch suspension containing small amount of KGM are expected to have a better stability in terms of texture and a better freeze-thaw tolerance.