Biodegradable Packaging from Whey Protein

Abstract

Biodegradable packaging films from whey protein concentrate were made in this study. A total of 46 formulations were made in the form of thin (50 - 120um) films by using solvent casting. Additives used in the formulations included plasticizers i.e glycerol and propylene glycol, chaotropic agent i.e guanidine thiocynate, gelation and crosslinker i.e glutaraldehyde. Tensile tests showed an increase in tensile strength with the addition of glutaraldehyde (1.2 v/v) and gelatin (upto 50% wt%). Addition of glycerol, propylene glycol and guanidine thiocynate increased elongation of films. Water vapor permeability and oxygen permeability of films containing glycerol, propylene glycol and guanidine thiocynate increased, while films made with gelatin, glutaraldehyde showed lower permeability for oxygen and water. Glass transition temperature was measured by DSC and results showed consistent decrease in Tg with increasing amount of plasticizer and chaotropic agent. Biodegradability was measured by degradation in 1% pancreatin. Results showed lower degradation time for formulations containing increasing proportions of glutaraldehyde and gelatin. Fourier transform infrared spectroscopy (FTIR) was used to evaluate changes in covalent bonding post glutaraldehyde crosslinking. Peaks corresponding to stretching of imine bonds were found at 1590 cm-1 suggesting crosslinking reaction between glutaraldehyde and terminal amine residues of whey/gelatin. Scanning electron micrographs showed an increase in relative porosity for compositions containing glycerol when compared to formulation containing only whey. Surface micrographs of formulations with gelatin showed phase separation. The phase separation may be attributed to partial immiscibility of whey with gelatin.