Hygroscopic Behavior and Thermodynamic Properties of Ziziphus joazeiro Mart. Kernel Flour

Abstract

The hygroscopic and thermal behavior of kernel flour from Ziziphus joazeiro fruits were investigated. Adsorption isotherms were obtained at temperatures of 293, 303 and 313 K and adjusted to GAB, Oswin and Peleg models. The best fit of the experimental data was obtained with the GAB model with R² values> 0.994 and mean percentage deviation P <10%. The isotherms obtained were sigmoidal type II. Isosteric heat and other thermodynamic properties were calculated as a function of moisture content. Adsorption isosteric heat decreased exponentially with increasing moisture content and differential entropy increased with moisture content, while differential enthalpy decreased. The theory of compensation confirmed that these properties are dependent on moisture content. The isotherms presented a spontaneous and enthalpy process.

Influence of high hydrostatic pressure ( HHP ) pretreatment on plum ( Prunus salicina ) drying: Drying approach, physical, and morpho‐structural properties of the powder and total phenolic compounds

“…The shape of the adsorption isotherms powder plum estimated using the GAB model (Figure 3) is which is characteristic of type II curves (Brunauer et al, 1940;Zeymer et al, 2017). This type of isotherm can be classified into three regions: the first corresponds to the moisture of the monolayer strongly linked to the product matrix; the second is almost linear, corresponding to the water at the material multilayer; the third region is related to the free water available for chemical reactions (Polachini et al, 2016;Silva et al, 2020). Notes: X m is the water content in the molecular monolayer; C, K is the parameters that depend on the temperature and the nature of the product; a, b is the model parameters and k 1 , k 2 , n 1 , n 2 are the model constants.…”