Optimization using the desirability functions
Optimum conditions for paper coating were determined to
obtain minimum WVP and maximum TS and %E. For all types of
coated paper, a maximum level of coating weight and level of glycerol
concentration within range of 18.72–26.11% were found to be
optimum for minimum WVP and maximum TS and %E (Table 5). For
chitosan-coated paper, desirability score of 0.9854 was obtained
when WVP, TS and %E values were 299 g m m−2 d−1 kPa−1,
30.50 MPa and 5.15%, respectively. These values were obtained
when the independent variables, i.e., glycerol concentration and
coating weight were 20.42% and 4.55 g/m2, respectively.
Kjellgren et al. (2006) studied the conditions necessary to obtain
good barrier and surface properties of chitosan-coated greaseproof
paper. A coating weight of 5.2 g/m2 was required to obtain a packaging
material with good barrier properties against oxygen, nitrogen,
carbon dioxide and grease as well as high fracture strain.
For each biopolymer used, the obtained value of desirability
(>0.95) shows that the estimated function may represent the experimental
model and desired conditions (Table 5).
The results of simultaneous optimization parameters, for each
biopolymer used, were validated by repeating the experiment at
the conditions predicted. The comparison between predicted and
experimental values showed excellent correlation. The predicted
and experimental responses were not significantly different at 5%
significance level.