Experiments were carried out according to the Box–Behnken
experimental design, in order to study the combined effects of
the independent variables (Starch, glycerol, agar, and span 80) on
the mechanical properties (tensile strength (TS), elongation (E),
Young’s modulus (YM), puncture force (PF), and puncture deformation
(PD)) of the tapioca starch based biodegradable edible films
and the measured responses are listed in Table 2.
A system with several variables is primarily affected by some of
the main effects and low order interactions. It may be assumed
that the higher order interactions are small relative to the low
order interactions; therefore, in the present work only two-way
interactions were considered. Linear, interactive, quadratic, and
cubic models were fitted to the experimental data to obtain the
regression models. To decide about the adequacy of models among
various models to represent mechanical properties of the starch
based biodegradable edible films, two different tests namely the
sequential model sum of squares and model summary statistics
were carried out in the present study and the results are given in
Tables 3 and 4.
The fit summary of the output indicates that the quadratic
model is statistically highly significant and the p-value was
lower than 0.0001. This means that at least one of the
terms in the regression model has a significant correlation