Enhancing Water Resistance, Tensile Properties and UV-Shielding Capacity of Bovine Gelatin Films Modified with Epoxidized Soybean Oil and Glyoxal during Processing

Abstract

The present work is focused on the use of epoxidized soybean oil (ESO, 10 wt%) as hydrophobizing additive, glycerol as plasticizer (Gly, 30 wt.%),and glyoxal (GLX, 2 wt%) as low-toxicity cross-linking agent to endow bovine gelatin (BGe) films with improved moisture-related and UV-light barrier properties. Therefore, we aimed to investigate the effect of such modifications on the physicomechanical and structural properties of the ob-tained gelatin films. Modification was produced during intensive mixing and hot-press molding as a more environmentally sound and less time-con-suming processing method. ESO improved moderately the moisture content (MC) and water vapor permeability (WVP) of BGe film by 19% and 29%, respectively, but the total solubility of BGe-10ESO film evidenced the inability of ESO to induce covalent cross-linking. When GLX was add-ed to the BGe-10ESO formulation, several target film properties were upgraded; the film kept about 78% of its weight after 24 h of soaking in water, WVP improved by 56.8%, the tensile strength (TS) increased 48% while the stretching ability dropped in about 41%. The significant reduction in available free amino groups, from 100% (control) up to 21.9%, together with the increased color from light yellow to light orange confirmed that amino groups in BGe were involved in imine-based cross-linked structure when treated with glyoxal. Further, the high blocking ability of BGe-10ESO-2GLX film against UV-radiation may be useful in delaying UV-induced lipid oxidation when it is placed in contact with foods.