Measurement of dynamic rheology during ageing of gelatine–sugar composites

The effect of sugars (sucrose, glucose and xylose) at different concentrations (0, 10, 20, 30, 40 and 50%) on the dynamic rheological properties of gelatine (2% w/w) was investigated during ageing. Storage moduli (Gʹ), when measured at 5 °C, decreased with increasing concentration of added sugar. Xylose was found to induce the greatest reduction in the values of Gʹ. Gʹ values, measured as a function of ageing time (10 h) at 5 °C, increased rapidly at the initial stage and then reached a pseudoplateau region after long ageing times. Increasing the sugar concentration resulted in a decrease in the pseudoplateau values. The rate constant (K) for structure development of gelatine during ageing was described by apparent first-order kinetics. Gʹ and K values in gelatine–sugar composites increased in the following order: xylose (less than) glucose (less than) sucrose. The magnitudes of Gʹ at the end of ageing were much greater than those of Gʹ, showing a small dependence (slope = 0.005–0.088) on frequency (omega).