Effect of water activity and temperature on thermal behaviour, specific heat and sorption isotherms of potato and carrot [electronic resource].

Includes references.

Differential scanning calorimetry (DS C) technique was applied separately or combined with thermogravimetry (TG) to study the effect of moisture content and temperature on thermal behavior and specific heat (Cp) values of potato and carrot. Gravimetric method was applied to establish the sorption isotherm curves of dried potato and carrot samples. Typical DSC- and TG- thermograms were obtained with one endothermal peak for moisture evaporation and several exothermal peaks for the decomposition of sugars, starch and fibre contents of the tested samples. Characteristic onset, peak and completion temperatures for each peak are included. For the drying process, it could be recommended not to use air temperatures higher than 140°C for carrot and 180°C for potato. Specific heat of both vegetables increased with increasing moisture content and temperature. A mathematical model was developed to predict the Cp-values of tested material in relationship to moisture content and temperature. Sorption isotherm curves of dried samples showed sigmoid shaped curves with monolayer content of 0.069 and 0.141 kg H20/kg OM for potato and carrot respectively. Dried carrot samples showed higher hygroscopicity than that of potato. The obtained results are useful in designing drying processes and storage of potato and carrot.

Summary in Arabic.

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