Gelatinisation of starch in mixtures of sugars. I. Dynamic rheological properties and behaviours of starch–honey systems

Abstract

Dynamic rheological behaviour of starch–honey systems was studied using a strain-controlled rheometer. A dynamic temperature (30–130 °C) ramp test was used at 10 rad s −1 frequency, 1% strain, 2 °C min −1 ramp rate, 25 mm parallel plate, and 1.5 mm gap, using Wheaten cornflour TM and five honeys to generate 25 formulations (0.34–0.80 g water/g dry starch). G ′, G ″, and η ∗ increased upon gelatinisation, and they reduced as the honey content was increased. For all the formulations, G ′ was higher than G ″, and tan δ was generally less than 1.0. Key gelatinisation characterising temperatures (onset, peak and end) ranged from 96.0 to 122.3 °C, but did not vary much (CV<5%) for each honey irrespective of the concentration. The influence of water, fructose and glucose, singly and in combination, on gelatinisation indices (temperature and rheological parameters) was investigated. An exponential equation was employed to describe the relationship, and relevant parameters were obtained. The consequences of the observations in the study are discussed particularly as they relate to extrusion of such systems, and possible interactions between fructose and glucose in the starch–honey systems.