EVALUATION OF MONOLAYER MOISTURE CAPACITY AND THE ENERGY CONSTANT OF SOME POWDERED SPICES BY USING BET AND GAB MODELS
Abstract
BET equation (IUPAC standard) and GAB equation (European Project Group on physical properties of food recommendation standard) for monolayer capacity value evaluations were used for testing the moisture adsorption experimental data of powdered white and black papper, cloves, nutmeg and cinnamon. The BET equation fits only up to aw = 0.44, while the GAB isotherm fits and covers a much wider range (0.06w <0.97). the mean relative percentage deviation modulus (E) were in the range of 1.13% < E < 2.73% for GAB and 16.21% < E 26.60% for BET, indicating the marked dependency of the BET sorption isotherm curve on the regression range as well as its typical upswing that began at water activity value equals to 0.6. It was also found that the values for water content adsorbed in the monolayer, expressed as the mass of water adsorbed on 100 gram dry-matter of sample, obtained by the GAB equation were higher than those obtained by the BET model but the energy constant value of BET that were higher than the GAB vakue was observed only for black pepper sample.