Influence of Sorbitol and Glycerol on Physical and Tensile Properties of Biodegradable-Edible Film From Snakehead Gelatin and κ-Carrageenan.

Abstract

Two plasticizers with distinct properties are carefully studied in this research for their suitability in creating biocomposite edible film products. The study uncovers films' physical, tensile, and biodegradability attributes, using snakehead gelatin and ĸ-carrageenan in different concentrations, with sorbitol or glycerol as plasticizers. The biomaterials of the edible film consist of snakehead gelatin (Channa striata) 2% (w/v); ĸ-carrageenan at concentrations of 1%, 1.5%, and 2% (w/v); and sorbitol/glycerol 15% (v/v). The addition of ĸ-carrageenan up to 2% in the formulation increased the film thickness to 0.046 ± 0.005 mm, tensile strength to 2.05 ± 0.56 MPa, and elongation at break to 35.00% ± 2.92% while decreasing the water vapor transmission rate (WVTR) to 0.17 ± 0.00 g/mm²/h (p < 0.05). The effect of glycerol in the composite did not affect thickness and luminosity (L ^∗) (p > 0.05), but the tensile strength increased from 0.18 ± 0.17 to 1.03 ± 0.40 MPa (p > 0.05). Sorbitol increased the value of color difference, elongation at break, and WVTR, namely, 19.77 ± 1.02, 25.20% ± 1.79%, and 0.28 ± 0.02 g/mm²/h, respectively (p < 0.05). The swelling index of the films increased with ĸ-carrageenan concentration, whereas the water content decreased (p < 0.05). The addition of sorbitol reduced the solubility of the film from 71.43% ± 12.39% to 42.67% ± 15.44% (p < 0.05), while glycerol did not affect changes in film solubility (p > 0.05). The presence of sorbitol had no significant effect on the contact angle (p > 0.05) and was more affected by the addition of glycerol at higher ĸ-carrageenan concentrations (p < 0.05). The ability to decompose after 28 days was more remarkable for films containing glycerol than sorbitol. Fourier transform infrared analysis revealed the functional group structures of all samples, indicating that no new compounds were formed in them. The surface structure of the sorbitol-plasticized film was predicted to be rougher and easily cracked, but more compact and dense, while the glycerol-plasticized film tended to be smoother with fainter cracks due to its hygroscopic properties.