Empirical modeling of moisture sorption characteristics and mechanical and barrier properties of cassava flour film and their relation to plasticizing-antiplasticizing effects

Moisture sorption kinetics of cassava flour film was investigated at various relative humidities (RH). Their curves were fitted to a Peleg model. This film was also studied for its sorption isotherm. Empirical models were tested to fit the experimental data. Moisture sorption was more rapid in the initial stages; less moisture was adsorbed as adsorption time increased. GAB and Lewicki models were found to be better-fitted models. Effects of sorbitol concentration and RH on mechanical properties of films were examined. The tensile strength (TS) of films vastly decreased with increasing sorbitol concentration. The percentage of elongation increased significantly with increasing sorbitol content; however, it declined when sorbitol content was above 40 g/100 g. Modulus of elasticity (E) of films displayed a similar trend to TS. The E of this film was inversely linear to RH, whereas its elongation was exponentially proportional to RH. Effects of sorbitol concentration on barrier properties of films were also examined. The water vapor transmission rate of film was gradually reduced with increasing sorbitol content; however, it dropped dramatically with sorbitol content above 40 g/100 g. The oxygen transmission rate of film significantly decreased with rising sorbitol content. This is helpful in understanding the performance of edible films under varying RH conditions and plasticizer contents. (C) 2012 Elsevier Ltd. All rights reserved.