Thermally stimulated luminescence technique for compositional change in food materials: a new approach in thermal analysis

Structural changes are normally studied using the well-known techniques such as TGA, DTA, DSC etc. An attempt is made in the present studies to use thermally stimulated luminescence (TSL) technique for monitoring these changes in food products such as rice and wheat powders. These materials, in the form of fine powders, are subjected to heating cycle in the temperature range of 300 -700 K using the heating rate of 6.66 K/sec. The TSL emission is monitored concurrently using a TSL apparatus equipped with PC based operation facility. It is seen that a well-defined TSL peak around 575 K is observed in these samples. It is associated with the evolution of gaseous fumes, which in turn, may result in changing the composition of the material under study. The TSL peak is interpreted as due to an intermediate compound between carbohydrate and oxide (formed on charring of material at 700 K). On irradiation of the virgin materials with β emission obtained from 90Sr source for short duration of 5 minutes, the peak intensity shows a steep rise over the unirradiated samples. The irradiation effect is however, removed on storage of these samples for 24 hours. (author)