GAB Model

Moisture sorption isotherms are described using the GAB model, which is defined as Where:

• m₀ is the monolayer moisture content (kg H₂O /kg total solids)
• C is a constant related to the heat of sorption of the first layer
• K is related to the heat of adsorption of the multi-layer
• a_w is the water activity

The parameters (C, K and a_w) can also be described as a function of temperature using the Arrhenius equation. Where:

• T is the absolute temperature
• R is the universal gas constant, 8.314 J/mol-K
• m_G,C₀,K₀,q_m are constants for the temperature effect
• λ is the heat of condensation of pure water
• H_m and H_n are the heat sorption of the monolayer and the multilayer of the water, respectively

The mechanical properties of almonds are fitted using the Simple Fermi's distribution. Where:

• Y(a_w) is the mechanical property of almond at water activity a_w
• Y₀ is the mechanical property of the sample at dry state
• a_wc is the water activity when a drastic textural echange occurs
• b is a dimensionsless constant