Moisture Sorption Isotherm of Cassava Starch Film Incorporated with Kaffir Lime Oil

Abstract

The use of bioplastic film has been gaining a lot of interest especially in food packaging, however knowledge on its stability during handling is limited. Moisture sorption isotherm is a study that determines the stability of the film when exposed to certain environmental conditions. The gravimetric method was used to determine the moisture sorption isotherm of cassava starch film incorporated with kaffir lime essential oil (EO) at 30°C and 40°C. The moisture content increases with increasing water activity for both 30°C and 40°C. The sorption data were fitted into 3 models and Oswin was found to be the best model to fit the data with R2 of 0.93 to 0.97. The sorption data were used to determine the net isosteric heat of sorption (qst) through the application of Clausius – Clapeyron equation which provides an approximation of the minimum energy required to remove water from a solid. Generally, the qst decreases exponentially with an increase in moisture content regardless of whether the film contains EO. The incorporation of EO within these temperatures does not affect the moisture content and heat of sorption of the starch-based bioplastic film, which shows its stability and potential as an additive in food packaging film.

Keywords

• sorption isotherm model
• isosteric heat
• biopolymer plastic
• moisture content
• kaffir lime essential oil