Hygroscopic behaviour of cassava flour from dry and water groups

Cassava flour from dry and water groups are important starch products widely consumed in the Amazonian region of Brazil. In this study, the moisture sorption isotherms of cassava flour from dry and water groups were obtained in the water activity (a(w)) range from 0.09 to 0.94 (dry group) and 0.07 to 0.93 (water group) at 25 degrees C and the applicability of eight mathematical models in data prediction was evaluated. Both cassava flour from dry and water groups exhibited type II isotherms (sigmoid) and the hysteresis effect between adsorption and desorption isotherms was shown almost over the entire range of a(w). The moisture of cassava flour from dry and water groups should not exceed 11.3g H2O 100g(-1) (a(w) = 0.6) to ensure the theoretical microbiological stability and the monolayer moisture value (9.0 and 7.9 g H2O 100g(-1), respectively) indicated the level of moisture content to be reached during the drying process to avoid unnecessary power consumption. Finally, the data fit showed that the mathematical model of GAB were able to predict efficiently the sorption isotherms of both cassava flour from dry and water group at the entire aw range.