Sorptional equilibrium and drying characteristics of garlic

Drying characteristics of garlic including moisture sorption equilibrium drying kinetics and pungency losses were investigated Adsorption and desorption isotherms at 25, 45 and 65 degrees C were determined and correlated with a four parameter equation. The influence of temperature on adsorption was negligible and some hysteresis effect was observed. Air drying experiments and a diffusive model taking into account the internal and external resistances to mass transfer were used to evaluate effective diffusivity and energy of activation for diffusion. The effective diffusivity increased with temperature, ranging from 1.54 to 3.45 10(-10) m(2)/s in, the wet zone and from 0.34 to 0.58 10(-10) m(2)/s in the dry zone. The effect of air velocity air relative humidity and sample thickness on drying kinetics was also studied. Changes in garlic flavor or pungency during dehydration as a function of temperature, based on determination of pyruvic acid, was measured and modeled as a first-order reaction. At higher temperatures the enzymatic pyruvic acid decreased faster than the total pyruvic acid. (C) 1997 Elsevier Science Limited. All rights reserved.