Moisture sorption isotherms of figs with and
without glucose syrup (at 20% and 40%, w/w) were
determined at 5 °C, 25 °C, and 40 °C. A static gravimetric
method was used under 0.11–0.84 water activity ranges for
the determination of sorption isotherms that were found to
be typical type ΙΙΙ for control sample. The inclusion of
glucose syrup had significant effects on the sorption
isotherms, and the moisture content of samples at each aw
decreased with increasing temperature. The experimental
data were fitted well with two-parameter Brunauer–
Emmet–Teller, three-parameter Guggenheim–Anderson–de
Boer, and four-parameter Peleg models that all had R2 of
greater than 0.99. The net isosteric heats of sorption were
estimated using the Clausius–Clapeyron equation from the
equilibrium data at different temperatures. It was found that
the addition of glucose syrup significantly increased the
amount of monolayer water and the isosteric heat of
sorption. Both water activity and isosteric heat of sorption
increased with glucose syrup level and the shape and status
of sorption isotherms tend to change toward the typical
sigmoid shape of most food systems.