The present investigation was carried out to apply a detection method of some irradiated spices using thermal analysis technique. Black pepper, cumin and ginger were irradiated using γ- irradiation at dose levels 5, 10 and 15 kGy, and stored for 12 months at room temperature. Thermal analysis techniques TGA and DTA were studied for characterizing irradiated spices. Thermo gravimetric analysis (TGA) is a method where the measurement of mass as a function of heating is recorded. TGA was used to determine the moisture and ash contents and thermal stabilities. Nonsignificant changes of the weight loss percent due to the irradiation occurred on the studied spices up to 10 kGy . The weight loss decreased at the first step up to 100 oC due to the release of water of hydration. Another sharp decreasing in weight loss percent at the second step 220- 300 oC may be due to volatilization of the sample. The final weight loss weight loss stage up to 500 oC may be due to burn out the fixed carbon remaining in the sample. As the irradiation dose increased from control up to 15 kGy, the weight loss percent at the dehydration step increased.
The kinetics of the spices decomposition were studied in order to ascertain the type of weight loss mechanism and calculate the activation energy Ea .
The differential thermal analysis DTA of the studied samples showed two main characteristic peaks, endothermic one due to the dehydration process and the second peak may be due to the partial volatilization of the aromatic compounds of the main constituent of the studied spices. Finally, it could be recommended that using γ- irradiation (up to 10.0 kGy) for black pepper, cumin and ginger are thermally stable to human consumption.
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