Zein electrospun fibers purification and vanillin impregnation in a one-step supercritical process to produce safe active packaging

In recent years, the search for advanced packaging solutions has been oriented towards systems capable of extending the food shelf-life. One of the most interesting strategies is that of active packaging capable of releasing, in a controlled manner, antioxidant and antimicrobial agents. In this paper, the combined use of two promising alternative methods: i.e., electrospinning and supercritical fluids impregnation is proposed for the production of active packaging in order to overcome limitations of conventional packaging production methods that can restrict the diffusion of novel packaging solutions oriented towards natural sources. Zein fibers produced by electrospinning were selected as bio-based polymeric support. The incorporation of vanillin into zein fibers, as natural antimicrobial active agent, was performed in two different ways: directly during the electrospinning process and after zein fiber formation by supercritical fluids impregnation. In the first case, the electrospinning of vanillin and zein solution allowed the direct formation of a fibrous structure of zein loaded with vanillin; in the second case, vanillin, dissolved in supercritical carbon dioxide, was impregnated onto the fibrous zein structure. At different operating conditions, a vanillin loading in the range 3.78–11.33 % was obtained, independently of the technique. Through the characterizations of the package components produced and the study of the release kinetics of the active agent, it emerged that the two methods used permit a calibration of the migration kinetics allowing to obtain an active food packaging with controlled and modulable release according to the final application. Comparing the two processes, it is possible to note that, in the case of the supercritical impregnation, a controlled release of the active principle was obtained, whereas a fast release kinetics was observed using the electrospinning process.