Comparative Effect of Different Plasticizers on Barrier, Mechanical, Optical, and Sorption Properties of Hydroxypropyl Methylcellulose (HPMC)–Based Edible Film

Abstract

Identifying ideal plasticizer is pivotal to develop a biopolymer-based edible films for food packaging. The effect of different plasticizers (glycerol, polyethylene glycol, sorbitol) on the mechanical, water vapor barrier, optical, and moisture sorption properties of hydroxypropyl methylcellulose (HPMC) -based flexible films was examined in this study. Mechanical properties and water vapor permeability (WVP) of films were determined using standard ASTM methods. Moisture sorption isotherm (MSI) for different HPMC films were obtained thermogravemitically and seven sorption models were fitted to experimental sorption data through nonlinear regression using curve fitting tool in MATLAB R2015b and goodness of fit of these models was compared based on Akaike information criterion (AIC). GAB model was used to determine the monolayer moisture content and heat of sorption of different films. Plasticizing efficacy of different plasticizers was significantly different for HPMC film in studied concentration range. Water vapor permeability (WVP) for native HPMC film was 0.451 g mm/kPa m2 h, which further increased to 0.972, 0.890, and 0.615 g mm/kPa m2 h when 25% (w/w of HPMC) glycerol, PEG, and sorbitol were added as plasticizers, respectively. GAB model showed an increase in monolayer moisture (M0) content with increasing plasticizer concentration and the highest M0 value was observed for glycerol-plasticized film. Added plasticizers were found to be effective in providing desirable flexibility in terms of elongation to HPMC film which is beneficial for coating and shrink wrap packaging application but adversely affect the tensile strength and transparency of film. Henderson and Oswin models were selected as the best fit model to the experimental sorption data based on AIC values. The findings from the current study would serve in selection of suitable plasticizer for HPMC-based film/coating in food packaging applications.