Gelatinisation and Retrogradation Behaviour of Some Starch Mixtures

Abstract

Differential scanning calorimetry (DSC) and dynamic rheological measurements were used to characterise the behaviour of potato-waxy maize, potato-barley and waxy maize-barley starch mixtures. Gelatinisation and retrogradation were studied at two starch concentrations, 20% (w/w) and 50% (w/w). In the DSC gelatinisation thermograms of the mixtures it was possible to recognise features of the thermograms of the individual components, indicating that each starch gelatinised independently of the other starch in the mixture. The retrogradation enthalpy was measured in the DSC after four and seven days of storage at 6 °C. The lowest values of retrogradation enthalpy for the mixtures were found for the waxy maize-barley and potato-barley mixtures, particularly at 20% starch concentrations and in the ratios 25:75 and 50:50, correspondingly. The retrogradation enthalpy measured for most starch mixtures corresponded to the calculated value, assuming that each starch contributed to the enthalpy according to its proportion in the mixture. Storage and loss moduli were measured for gelatinised starch suspensions during cooling from 90 to 6 °C, and then during a holding period at 6 °C for up to 6 h. The moduli for the mixtures were in most cases in between the values obtained for the individual starches.