2001 AACC Annual Meeting Charlotte, North Carolina October 14-18, 2001 Charlotte Convention Center

The stability of starch and starch-sugar systems containing less than 15% water (wet weight basis) was studied over a range of storage temperatures (T(a)) below their glass-rubber transition temperatures (T(g)). The sub-T(g) endotherm observed on the differential scanning calorimetry thermogram, which is associated with the enthalpy relaxation aspect of physical ageing was monitored in terms of its temperature and enthalpy in relation to T(g)-T(a). The sub-T(g) ageing was accompanied by an increase in the hardness of the samples as measured using isothermal dynamic mechanical thermal analysis (DMTA). Ageing kinetics parameters were obtained by applying to the modulus versus storage time data an approach similar to that proposed by Struik for creep compliance data on synthetic polymers. The widely used Tool-Narayaswamy-Moynihan model (TMN) for the describtion of the ageing of inorganics and synthetic polymer glasses was used to model the ageing process. The analysis revealed some of the difficulties in applying such models which are mainly due to the complexity of the glass-rubber transition behaviour of multi-components real and model food systems.