Effects of gelatin concentration and co-plasticizer type on physical, mechanical and microstructural properties of corn starch-gelatin composite edible films

Abstract

In the current study, corn starch-gelatin composite edible films varying in gelatin content (0, 5, 20%) were prepared by using glycerol, and citrate esters; tributyl citrate (TBC) or triisodecyl citrate (TIDC). Edible films formulated with different gelatin concentration and co-plasticizer type were characterized in terms of physical, mechanical, microstructural properties and FTIR spectra. Gelatin addition and increasing the gelatin concentration in the film formulation provided significant increases in surface hydrophobicity and tensile strength and significant decreases in thickness, and elongation at break values. Although the addition of gelatin significantly decreased the ΔE values, gelatin concentration did not affect the ΔE values of edible films. Co-plasticizer addition to the film formulation significantly increased the WCA, and elongation at break values, whereas it significantly decreased the thickness, ΔE and tensile strength values. Co-plasticizer type did not significantly affect the thickness, ΔE, WCA, and tensile strength of edible films. Gelatin addition to the film formulation increased the peak intensity at 1640 cm⁻¹, 1550 cm⁻¹ and 1240 cm⁻¹ bands and decreased the peak intensity at around 1000 cm⁻¹ band. According to the SEM results, addition of gelatin and/or co-plasticizer provided more compact and denser microstructure to the edible films. Overall, gelatin and co-plasticizer addition led to produce thinner edible films with more hydrophobic surface, more transparent appearance, and more ordered microstructure.