The optimisation of mechanical properties of fish gelatin as biodegradable films

Abstract

The mechanical characteristics of the biodegradable polymer are crucial to determine the application of the materials, especially as the packaging materials. This work reports the optimisation of the biodegradable polymer film formulation based on fish gelatin and glycerol on the tensile strength (Ts) and elongation at break (EB) of biopolymer film. The gelatin from the skin of tilapia fish is dissolved in 100 millilitres (ml) of distilled water and mixed with glycerol as a hydrophilic plasticiser, then cast and dried to produce films. The range contents of fish gelatin and glycerol used are 5.0 to 9.0 grams (g) and 10 to 20 % (w/w), respectively. This optimisation is done with central composite design (CCD) using response surface methodology (RSM). The maximum Ts of 27.625 MPa was found at formulation with 9.0 grams of gelatin and 10% glycerol, and the optimum EB of 44.578% was recorded at 9.0 grams of gelatin with 20% glycerol. These formulations exhibited only 5.12% and 0.60% error between actual and predicted values. Otherwise, Fourier transform infrared spectroscopy (FTIR) also demonstrated the achievable glycerol incorporated in fish gelatin film at 20% glycerol by hydrogen bonding in Amides A, I, II, and III mostly shifted to the higher wavenumber. This success can be seen from the aliphatic alcohol (C-O molecules derived from glycerol) peak around 1035 cm^-1 and 1029 cm^-1. The peaks shifted from 1029.99 cm^-1 to 1035.77 cm^-1 at 10% to 20% of glycerol. Otherwise, the successful incorporation of glycerol by decreasing intermolecular forces of films where peaks of Amide A became more intense, wider and sharper.