Premium
Water sorption isotherms and thermodynamic properties of pearl millet grain
Author(s) -
Goneli André Luis Duarte,
Corrêa Paulo Cesar,
De Oliveira Gabriel Henrique Horta,
Gomes Cassandra Ferreira,
Botelho Fernando Mendes
Publication year - 2010
Publication title -
international journal of food science and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.831
H-Index - 96
eISSN - 1365-2621
pISSN - 0950-5423
DOI - 10.1111/j.1365-2621.2010.02208.x
Subject(s) - sorption , thermodynamics , enthalpy , desorption , adsorption , equilibrium moisture content , relative humidity , chemistry , humidity , entropy (arrow of time) , moisture , physics , organic chemistry
Summary The water sorption isotherms of pearl millet grain and the thermodynamic properties obtaining during the process of drying pearl millet were examined. Equilibrium moisture content ( X eq ) was determined under several temperature ( T ) and relative humidity (RH) conditions. The X eq data were correlated by six mathematical models. The modified Henderson was the model that best fitted the experimental data. The X eq decreased with an increase in T at constant RH. Hysteresis was also studied; increasing T led to a decrease in this phenomenon. Integral isosteric heat of sorption ( Q st ), differential entropy (Δ S ) and the enthalpy–entropy compensation theory were studied. Q st values decreased when X eq increased because the Q st values of adsorption were lower than Q st desorption values. The values of Δ S decreased with increases in X eq , because Δ S values were higher for desorption than for adsorption. The enthalpy–entropy compensation theory is valid for describing the water sorption processes of pearl millet grain.