Abstract:
Water desorption isotherms of raw and osmotically dehydrated (at 25ºC, for 2 hours,
with 10 and 26% NaCl solutions) garlic slices at different temperatures (25, 40, 55, and
70ºC) were experimentally determined over a range of water activity of 0.05–0.90 using a
static gravimetric method. Desorption isotherms can be classified as Type III. The water
desorption isotherms of raw garlic clearly showed the influence of temperature i.e.
increasing water activity at a fixed moisture content with increasing temperature;
whereas for the osmotically dehydrated garlic the effect of the temperature was less
important. The increase of NaCl content in osmotically dehydrated garlic led to a
decrease in water activity at the same moisture content, and this effect was more
accentuated at high temperatures. Equilibrium moisture content data at each
temperature were satisfactorily fitted with Henderson model and a six-parameters
equation based on Henderson model was obtained in order to correlate simultaneously
moisture content with water activity, temperature, and osmotic solution concentration. A
prediction model based on concentration and physical state of garlic compounds was
successfully used to reproduce the experimental data.
Keywords: Drying, Equilibrium moisture content, Modelling, Water activity
