Models of moisture sorption isotherms for pelleted finishing broiler feed

To investigate the adsorption and desorption behavior of compound feeds, Guggenheim-Anderson-de Boer (GAB) equation and modified GAB were applied to fit the equilibrium moisture content (EMC) data of adsorption of a pelleted finishing broiler feed at equilibrium relative humidity (decimal, or water activity, Aw) from 0.11 to 0.97 and the desorption at water activities from 0.11 to 0.75 at 15℃, 25℃, 35℃ and 45℃, obtained by the conventional static gravimetric method. Both the equations gave excellent fitting goodness. EMC of the pellet feed reduced when temperature increased. Hysteresis existed between desorption and adsorption. Monolayer moisture content (Mm) from 15℃ to 45℃ estimated by Brunauer-Emmet-Teller (BET), fitting the desorption data, was between 6.34% and 5.39% (dry basis). The Mm reduced linearly with increasing temperature. Safe moisture content at the four temperatures, predicted by applying the modified GAB to adsorption and desorption data, was less than 13.09% and 14.71%, 12.92% and 14.33%, 12.74% and 14.00%, 12.56% and 13.66% (dry basis), respectively at Aw=0.65 as the critical point. The results give a reference for the feeds storage and cooling process.