Sorption isotherms of coffee in different stages for producing Turkish coffee

The aim of this research was to determine the adsorption behavior of coffee as green and roasted beans and ground. For this aim, the static gravimetric method was used and samples were kept in the different water activity levels between 0.01 and 0.91 at 25°C for 7 days. The data were evaluated using the BET (Brunauer‐Emmett‐Teller), GAB (Guggenheim, Anderson and deBoer), Halsey, and Peleg sorption equations. The constants m0 and C of BET and GAB equations were determined to be between 2.13 and 6.61 g water/100 g of dry matter and 30.05–429.60, respectively. The isotherms of all coffee samples were defined as Type II because the C constant of the GAB equation was higher than 2. Additionally; the BET, GAB, and Peleg equations were determined to fit better than the Halsey for adsorption properties of coffee because E% values were lower than 10% and the coefficient of regression values approached the 1.00. Practical applications The obtained results with that research could be useful for understanding the physicochemical relationship between water and dry matter of coffee. Because this relationship is quite important in foods that have easily changing characteristics and quality like coffee, and determination of their sorption characteristics ensures maintaining the physical, chemical, biochemical, and microbiological quality stability of food during processing, packaging, and storage.