(120e) Structural Relaxation of Powdered Amorphous Food Biomaterials

Understanding of structural relaxation of amorphous biomaterials either in powder or any other form is important from the point of view of determining their chemical stability and changes in their mechanical properties over the storage period. These properties can have positive or negative impacts on the product properties. The structural relaxation of non-equilibrium glassy state towards the lower energy state results into an exothermic enthalpy release over the time. This enthalpy can be analyzed by various thermo-mechanical techniques.

The objective of this research was to investigate the enthalpy relaxation of mixtures of food biomaterials at variable temperature and water activity conditions. A mixture of biomaterials composed of corn syrup solids, water and sucrose (at 4 ratios of corn syrup to sucrose) was boiled at 135oC to reduce the moisture content and to produce a glassy structure at room temperature condition. The boiled syrup was then poured on to the tray and cooled to room temperature. The vitrified structure was then ground to powder form. The powder was equilibrated at 0.11, 0.22 and 0.32 water activities at 23oC. The enthalpy relaxation occurred over the time was determined from the Differential Scanning Calorimetric (DSC) excess enthalpy shoot during glass-rubber transition. The relaxation kinetics followed the KWT function. The changes in these enthalpies suggest that the mechanical property of the powder such as compressibility, deformation and particle fracture property may change overtime.