The equilibrium moisture content of raw and blanched almonds of California grown “Carmel” variety was determined by using static gravimetric method at 25, 35 and 45C over a range of water activities (Aw) from 0.11 to 0.97. The sorption data were fitted to the Guggenheim–Anderson–de Boer (GAB) model. The goodness of fit of the model was evaluated by standard error of estimate, mean relative percentage deviation modulus and randomness of residual, which showed good fit of the GAB equation to the experimental data. The moisture adsorption isotherms of almonds exhibited type II sigmoid shape. Thermodynamic properties such as differential enthalpy and entropy were determined from moisture adsorption data by using the Clausius–Clapeyron equation. The results showed that enthalpy–entropy compensation theory was applicable for the moisture adsorption phenomena of raw and blanched almonds. The adsorption process of almond was enthalpy‐controlled. PRACTICAL APPLICATIONS Over 80% of the world almond production is grown in California and shipped to over 90 countries around the world. When exported to distant markets in the tropical regions, the physical, chemical and microbiological changes in almonds could cause the deterioration of food products due to environmental factors. Despite the large‐scale production and export of almonds, very little information on the sorption characteristics of almond varieties grown in California can be found in the literature. Reliable information on sorption isotherms is critical to designing optimum storage and shipping conditions to ensure desired levels of almond quality at consumption. This paper presents results from a comprehensive study of the sorption characteristics of one of the most important almond varieties grown in California, namely “Carmel.”

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Moisture adsorption characteristics of California grown almonds (Nonpareil: pasteurized and unpasteurized almonds; Monterey: pasteurized, unpasteurized and blanched almonds) were obtained using the gravimetric method over a range of water activities from 0.11 to 0.98 at 7-50ºC. The weights of almonds were measured until samples reached a constant weight. The relationship between equilibrium moisture content and water activity was established using the Guggenheim-Anderson-de Boer model. The diffusion coefficient of water in almond kernels was calculated based on Ficks second law. The monolayer moisture value of almonds ranged from 0.020 to 0.035 kg H2O kg-1 solids. The diffusion coefficient increased with temperature at a constant water activity, and decreased with water activity at a constant temperature. The thermodynamic properties (net isosteric heat, differential enthalpy and entropy) were also determined. The net isosteric heat of adsorption decreased with the increasing moisture content, and the plot of differential enthalpy versus entropy satisfied the enthalpy-entropy compensation theory. The adsorption process of almond samples was enthalpy driven over the range of studied moisture contents.

Moisture adsorption characteristics of California grown almonds (Nonpareil: pasteurized and unpasteurized almonds; Monterey: pasteurized, unpasteurized and blanched almonds) were obtained using the gravimetric method over a range of water activities from 0.11 to 0.98 at 7-50 o C. The weights of almonds were measured until samples reached a constant weight. The relationship between equilibrium moisture content and water activity was established using the Guggenheim-Anderson-de Boer model. The diffusion coefficient of water in almond kernels was calculated based on Ficks second law. The monolayer moisture value of almonds ranged from 0.020 to 0.035 kg water/kg solids. The diffusion coefficient increased with temperature at a constant water activity, and decreased with water activity at a constant temperature. The thermodynamic properties (net isosteric heat, differential enthalpy and entropy) were also determined. The net isosteric heat of adsorption decreased with the increasing moisture content, and the plot of differential enthalpy versus entropy satisfied the enthalpy-entropy compensation theory. The adsorption process of almond samples was enthalpy driven over the range of studied moisture contents.