Sorption and Thermodynamic Properties of Aromatic Plants as Drying Objects

Abstract

The high demand for aromatic herbs in the biotechnological, cosmetic, pharmaceutical and food industries led to increased requirements for the technological processes of processing aromatic raw materials to preserve biologically active substances and essential oils. Peppermint (Mentha piperita L.) is a well-known medicinal essential oil crop that is widely distributed throughout Ukraine. It is widely used due to its beneficial properties and therapeutic effect on the human body.
 The purpose of the article is studies of sorption and thermodynamic properties of aromatic plants to determine technological parameters of drying and storage processes, which ensure minimum specific energy consumption and maximum preservation of essential oils.
 The results of study on sorption properties of peppermint leaves are presented. Adsorption moisture isotherms of peppermint leaves were determined at three different temperatures 30, 40 and 50 ºC, using the standard gravimetric static method. The net isosteric heat of adsorption was calculated from moisture isotherms, using the Clausius-Clapeyron equation.
 The specific heat consumption for drying peppermint leaves at temperatures of 40 and 50 ºС was obtained experimentally, using the differential microcalorimeter of evaporation. The effect of volatile substances of peppermint essential oil on the heat of vaporization was revealed.
 The choice of drying temperature of aromatic plants is primarily determined by the thermal sensitivity of essential oils. The study of the effect of drying temperature on the removal of volatile aromatic compounds from peppermint leaves showed that the maximum allowable temperature of the material during dehydration should not exceed the melting point of menthol at 42,5 ºС.