Effect of storage conditions on the tensile properties of eco-friendly chitosan films by response surface methodology

The effect of temperature (4–50 °C), relative humidity (RH, 40–80%), and storage period (3–9 days) on the mechanical properties such as tensile strength (TS), percent elongation (%E) and modulus of elasticity (ME) of biodegradable chitosan film was studied by applying response surface methodology and Box–Behnken design of experiment. The results of ANOVA indicated that all the independent variables exhibited significant effect on the film properties. Temperature and RH exerted greater influence on TS and %E, while storage period showed moderate influence. Both linear and quadratic terms exerted significant (p < 0.01) effect, but total quadratic effect (p < 0.01) dominated over the total linear effect (p < 0.01). Simultaneous optimization by desirability approach was carried out on the independent variables to get the optimum levels within the experimental conditions. It was found that at 20 °C, 40% RH and a storage period of ∼7 days, the optimum values for TS, %E and ME were 35.8 MPa, 29.9% and 896.7 MPa, respectively. The predicted responses were validated and the difference between the predicted and experimental responses was not significantly different (p < 0.05).