Modelling of isotherms and their hysteresis analysis in gelatin from different sources

Sorption and desorption isotherms of four gelatin powder from different sources (Bovine B-225, Pig skin A-270, Fish FG-260 and Poultry PG-240) were determined at 25 degrees C by using the DVS machine at wide relative humidity range (0% to 90%). Data were fitted with the GAB and Peleg models. The isotherms showed the characteristic shape type II according to Brunauer classification. Both GAB and Peleg models fitted very well (R-2=0.999) to experimental data. Peleg model fitted much better at the desorption process. Monolayer values (m(o)) for GAB model resulted around 6% for sorption and 9% for desorption. FG-260 showed the higher hysteresis (10%) giving evidence of high difficulty in removing water from the porous capillary during desorption. B-225 resulted in much better storage stability with the lowest m(o) at the sorption stage (5.95%), and the best ability to remove water from the matrix during desorption (m(o)=9.30%).