Influence of Triple-Layer Furcellaran-Based Films Enriched with Walnut Oil Emulsion and Walnut Green Husk Extract on Storage Quality of Cod Liver Oil

Abstract

Triple-layer films based on furcellaran were designed. To give them antioxidant and UV barrier properties, an ethanol extract from walnut green husks (WGHE) was added to the third layer. In order to provide them with active and water vapor barrier properties, an emulsion based on walnut oil (WE) was added to the middle layer. The designed films were subjected to color analysis, UV–Vis spectra were determined, and opacity, water content, water solubility, water vapor transmission rate (WVTR) as well as contact angle were established. Thermal and mechanical properties, total phenolic content (TPC) and antioxidant activity (AA) were also assessed. Sachets containing cod liver oil were made from the films. The sachets containing cod liver oil were stored for 3 months at room temperature (22 °C) in direct sunlight and refrigerated (4 °C) without light. Acid, iodine and peroxide values were evaluated for cod liver oil samples (months 1, 2 and 3). The obtained triple-layer films differed significantly from the control film in terms of antioxidant properties, color and mechanical properties. It was found that the films containing WE and WGHE had a darker color, a higher light barrier, a seven-fold higher opacity and lower water content compared to the control film without WE. The water content ranged in scope from 41.54 (control) to 24.40 (FILM 3). WVTR did not change under the influence of the WE/WGHE. The use of WE and WGHE increased the TPC and AA of the designed films. The average TPC and AA values of WE and WGHE enriched films were 281.4 mg GAE/100 g and 0.5 mmol TE/100 g, respectively. It was found that the values for the quality parameters changed during storage of the cod liver oil samples. A significant increase in the peroxide value was observed, particularly in the cod liver oil samples stored in light conditions. However, the incorporation of walnut oil and walnut green husk extract into the films did not enhance the oxidative stability of cod liver oil, indicating limited effectiveness of the developed active packaging system under the tested conditions. Further research is needed on other food products, e.g. preferably dry ones.