Models of Sorption Isotherms for Food: Uses and Limitations

Abstract

Moisture sorption isotherms describe the relationship between moisture content and water activity in food. This work presents basic concepts related to the sorption thermodynamics of water, the classification of isotherms, “uses and limitations of the models”, and measurement of sorption isotherms for food materials. The most commonly used models in food are Brunauer-Emmett-Teller and Guggenheim-Anderson-de Boer. The success of the Brunauer-Emmett-Teller model is rather qualitative, considering that almost all cases are linear only in a limited rank of water activity from 0.05 to 0.45, as its main applicability is the estimation of surface areas. And, the use of the Guggenheim-Anderson-de Boer model is generalized by its theoretical bases, mathematical simplicity, and ease to interpret; but it is not frequently used when the water activity greater than 0.93.

Linking vegetation to climate using ecosystem pressure-volume relationships

“…Water potential is a measure of free energy, or chemical potential energy, of water and as such the relationship between water potential and water content is of interest in a variety of contexts and media, e.g., leaves (Tyree & Hammel 1972), wood (Meinzer et al 2003a), rocks (Franzen & Mirwald 2004), soil (Brooks & Corey 1964), even food (Andrade P et al 2011)see Box 2 for a Summary of Water Potential in the Environment. The product of pressure and volume (Ψ•θ) represents the difference in potential energy from the same volume of pure water (Gibbs 1906).…”

“…Water potential and water content are physical properties that can theoretically be characterised in any object and system (Tyree & Hammel 1972;Franzen & Mirwald 2004;Andrade et al 2011), and at any spatial scale. One challenge with characterising an ecosystem water potential (ΨE) is in accounting for the spatial and temporal variability, including steep gradients that occur throughout the vertical profile of transpiring vegetation.…”

Impact of phase change materials on lightened earth hygroscopic, thermal and mechanical properties

“…The moisture sorption isotherms reported in Figure 3 show, for each investigated material, evolution of moisture content versus ambient air relative humidity at a constant temperature of 23 °C. According to Brunauer's proposal [60], the sorption curves correspond to the type III and show hysteretic loops. Such kind of curves is typical of porous materials, as the investigated soil-fiber mixtures.…”

The Effect of Drying Temperature and Thickness on the Drying Kinetic, Antioxidant Activity, Phenolic Compounds, and Color Values of Apple Slices

“…Te BET model gives the most suitable results in water activity values between 0.05 and 0.45, however, our water activity values are not in this range. It may be the reason for low R 2 values[40]. For both thicknesses, it can be said that the GAB model is the best model for the determination of the desorption behavior of apple slices with the highest R 2 value.…”