Preparation of eco-friendly composite food packaging films based on gelatin and a matrine coconut acids ionic liquid

In this study, we developed an environmentally friendly food cling film that exhibits a high antioxidant and antibacterial performance, wherein a novel ionic liquid (IL) of matrine and coconut acids ([Mat][Coc]) with excellent antioxidant and antibacterial properties was applied to a gelatin-based film to improve its mechanical and bioactive properties. As a result, 78.9% inhibition of Escherichia coli was observed at a [Mat][Coc] concentration of 10%, and a scavenging capacity of over 90% was seen in both DPPH and ABTS radicals. Additionally, the gelatin/[Mat][Coc] (Gel/MC) composite films possess hydrogen bonds between the amino groups of gelatin and the carboxylic oxygens of [Mat][Coc], which works as a plasticizer and resulted in a high visual transparency (>90%), strong thermostability (initial thermal decomposition temperature, >200 °C), and low water vapor permeability (WVP, 0.0719–0.1798 × 10−11 g m−1 s−1 Pa−1) in the Gel/MC composite film with 5–30% [Mat][Coc]. At a [Mat][Coc] concentration of 5–10%, the Gel/MC film exhibited a tensile strength and elongation that were 1.98–7.94 and 1.62–4.06 times, respectively, that of pure gelatin. Moreover, it was observed that Gel/MC films with a 5–10% concentration of [Mat][Coc] significantly reduced the browning and the weight loss rate of apple slices wrapped in the film. The above results indicate that the addition of [Mat][Coc] to gelatin-based films is a promising technique to develop eco-friendly food packaging that keeps food fresh.