Moisture sorption of cassava starch film incorporated with kaffir lime oil and the prediction models

Abstract

Biopolymer films have attracted interest in food preservation and packaging. Moisture content is a necessity to determine product stability at different storage conditions. In order to understand the behavior of film at different environmental conditions, moisture sorption isotherm at various water activity should be performed. The moisture sorption of cassava starch film with the incorporation of kaffir lime oil was measured by the gravimetric method at 30±1 °C using several salt solutions that provide ranges of relative humidity conditions. The equilibrium moisture content increased with increasing water activity. The addition of kaffir lime oil did not give much influence on the equilibrium moisture content of the film at targeted water activity. The fitting of the sorption data to GAB, Smith, Oswin and Halsey model shows that all models were accepted to describe the moisture sorption of cassava starch film with kaffir lime oil. According to the coefficient of determination (R2), the Smith model showed a perfect fit with R2 ≥ 0.98, followed by the Halsey model (R2 ≥ 0.97), Oswin model (R2 ≥ 0.94) and GAB model (R2 ≥ 0.89). The root mean square error (RMSE) values for the Smith model were the very least as compared to other models. The percentage of mean relative error (% MRE) of Halsey and GAB model show the best fit with a value less than 5 %. The Halsey model was well correlated to the moisture sorption data with a high value R2, less value of RMSE and a low % MRE. The moisture sorption of the film can be further correlated to other physical and mechanical properties of the film.