Moisture Sorption Isotherm and Isosteric Heat of Dried Cabya (Piper retrofractum Vahl) Powder

Abstract

Cabya (Piper retrofractum Vahl) is a widely utilized herbal plant for Indonesian traditional medicine. Up to date, the commonly applied storage method for this plant is in dried form, and makes it less effective for distribution process and less attractive for consumers preference, i.e. consumers usually prefers to consume herbal product in powdered form. In the attempt to provide an optimized storage condition of dried cabya powder, the study was conducted to analyze the sorption isotherm behavior of dried cabya powder and to obtain the fittest sorption isotherm model by comparing obtained data to five commonly used sorption isotherm models, i.e. BET, Oswin, Smith, Caurie, and GAB model. The sorption isotherm data was obtained using static gravimetric method in 24 h of interval weighing observation. Six saturated salt solution, i.e. KOH, MgCl2, KI, NaCl, KCl, and KNO3 were employed for water activity (aw ) in the range of 0.063 - 0.936. The observation was conducted at three different temperatures, i.e. 25±2°C, 35±2°C, and 45±2°C with triplicates. The results indicated that GAB model satisfactorily describe the sorption isotherms behavior of dried cabya powder. The mathematical form of isosteric heat equation of dried cabya powder in adsorption and desorption were also presented.

Experimental Investigation of Moisture Sorption Isotherms for Mefenamic Acid Tablets

“…The values of EMC for desorption were higher than those for adsorption at constant water activity, this behavior was an indication of the appearance of hysteresis phenomenon and it was noticed for other pharmaceuticals [13,16,18,28]. Fig.…”

“…During desorption, the pores were saturated at the beginning then water diffusion occurred from the periphery to the surface and that when the partial pressure of the water vapor in the surrounding air became lower than the vapor pressure inside the capillary. The value of hysteresis is the difference of equilibrium moisture content between desorption and adsorption [14,15,16].…”

“…The experimental EMC data of the tablets were determined using the static method. It is based on generating a fixed relative humidity environment using saturated salt solutions, where the samples are brought to equilibrium in a closed system of known relative humidity [16]. The relative humidity value depends on the salt kind.…”

Moisture sorption and thermodynamic properties of Camellia oleifera seeds as influenced by oil content

“…The moisture sorption isotherm is generated when the relationship between relative humidity (related to the water activity (a w ) of the material at the equilibrium state) of the environment and equilibrium moisture content (EMC) of the food is expressed in graphical format with fixed temperature [2] . For desorption processes, moisture inside materials evaporates to the atmosphere with low a w and for adsorption processes, materials uptake moisture from the atmosphere with high a w .…”