Photothermal characterization of citrus essential oils and their derivatives

Photothermal techniques were used to study thermal diffusivity, thermal effusivity, thermal conductivity and specific heat of folded and non-folded citrus essential oils and their corresponding terpenes; the latter are derivatives of the folding process. Experimental results show that thermal properties of all citrus essential oils are comparable. However due to a decrease on d-limonene and other monoterpenes with the folding process, thermal properties of folded citrus oils are higher than those for unfolded citrus oils. Moreover, thermal properties of various citrus terpenes are lower than those of folded and unfolded citrus oils. Analysis of variance (ANOVA) reveals significant differences (p < 0.05) among means for thermal data with the folding degree and fruit type for citrus oils. Valued obtained in this work, most of them not available in the literature thus far, together with values expected to emerge from future photothermal calorimetric experiments, might be used in the modelling and design of distillation columns, reboilers and heat exchangers all being parts of equipment used for citrus oils processing at industrial scale.