Abstract
Improving functional properties of biopolymers for use as environment friendly packaging is an area of current interest. Biodegradable films with improved barrier and mechanical properties were prepared from methylated guar gum. Methylation resulted in structural modification of guar gum (GG) promoting greater crystallization thereby enhancing thermal stability towards decomposition. Reduction in radius of gyration (Rg), weight average molecular weight (Mw), and an increase in polydispersity index (PDI) were also observed due to methylation. Methylated guar gum (MGG) films exhibited 40% lower water vapor transmission rate (WVTR) as compared to control purified guar gum (PGG) films. Films prepared by partial replacement of PGG with MGG (10, 25, 50, 75 and 100% w/w) showed gradual improvement in percent elongation. The study gives an insight on the role of methylation in enhancing barrier and mechanical properties of GG based biodegradable films for possible application in food packaging.
Highlights
Serious environmental hazards posed by conventional petroleum-based packaging materials have led to an increased interest in recent years towards development of biodegradable packaging materials
The degree of substitution achieved in the earlier studies ranged from 0.1 to 1.7 while the corresponding value in the present study was 0.4 as determined by 1 H NMR
A protocol for green synthesis of methylated guar gum (MGG) replacing the use of conventional chemical solvents was established
Summary
Serious environmental hazards posed by conventional petroleum-based packaging materials have led to an increased interest in recent years towards development of biodegradable packaging materials. Lower mechanical strength and high permeability to water vapor as compared to petrochemical-based plastics are some of the drawbacks, which limit commercial use of biopolymers. Several physical methods such as UV curing, thermal processing[2], gamma irradiation[3,4], and addition of various additives[5] have been demonstrated to be useful for overcoming these limitations. We had earlier demonstrated that guar gum subjected to low dose gamma radiation (500 Gy) resulted in 33% improvement in tensile strength as compared to control gaur gum based films. Polar nature of carbohydrate based biopolymers including GG results in films with poor mechanical strength, barrier properties and sealability, thereby restricting their use as packaging material. The effect of methylation on thermal, mechanical and barrier properties of GG films were taken up for detailed investigation
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