Effect of far-infrared drying on the water state and glass transition temperature in carrots

摘要

The effect of far-infrared drying (FID) on the water state and glass transition temperature (T_g) of carrots were assessed by nuclear magnetic resonance (NMR) and differential scanning calorimetry (DSC). Results showed that, with increasing time, FID caused dramatic changes in the water state in dehydrated carrots. The drastically decreased content of free water in vacuoles was accompanied by sharp increases in the content of immobilized water in the cytoplasm and extracellular space. Subsequently, the content of immobilized water decreased gradually with increasing time. FID elevated the T_g values appreciably by decreasing the content of immobilized water in carrot tissues. In carrots with moisture content ＜0.39 g/g dry matter, T_g values were increased by 21.36, 35.55 and 40.99 ℃ with the moisture content decreased by 0.20, 0.25 and 0.30 g/g dry matter at respective infrared power values of 400, 600 and 800 W.