Electrospinning as a novel encapsulation method for food applications

Abstract

Electrospinning is a technology that comprises the application of electric power to elongate polymers into fibers with different range of diameters. The fiber mats so produced generally display high porosity and large-surface-area to volume ratios that enhanced the interaction with their surrounding media efficiently. The main objective of this work was to better understand the procedure of electrospinning as a one-step encapsulation approach to acquire active component loaded nanostructured biopolymeric fibers. In this PhD research, an overview on the impact of solution and processing parameters to the fabrication of zein electrospun fibers was investigated. The Ce value allowed determination of the minimum polymer solution concentration required for electrospinning of bead-free zein fibers which occured at 25 wt% (C = 2.1Ce). The response of RSM methods indicates that electrospinning parameters like concentration, solution feedrate and applied voltage had significant impact on the average fiber diameter. Gallic acid was used as the model active component to determine the performance of gallic acid loaded zein fibers using electrospinning as an encapsulation technique. The produced fibers exhibit diameters ranging from 327 to 387 nm. The fabricated gallic acid-zein fibers were appraised for various physicochemical characterizations including morphology of electrospun fibers, distribution of gallic acid in the electrospun fibers and thermal analyses. The interactions between gallic acid and zein, as well as antioxidant properties of gallic acid after electrospinning were investigated in order to increase further understanding on this system. Results obtained indicated that interactions occurred between gallic acid and zein at the molecular level. Nevertheless, the loaded gallic acid preserved its phenolic character and antioxidant activity after electrospinning. The fabricated product may contribute towards the development of nanostructured active packaging materials. Hence, evidence for the efficacy and effectiveness of gallic acid loaded zein electrospun fiber mat for food contact applications were determined by evaluating its release performance, mechanism of action, cytotoxicity and antimicrobial abilities. The Ze-GA fiber mats displayed similar rapid release profiles, with Ze-GA 20% exhibiting the fastest release rate in water as compared to the others. Gallic acid diffuses from the electrospun fibers in a Fickian diffusion manner and the data obtained exhibited a better fit to Higuchi model. The fast release profile of gallic acid from the electrospun fibers is due to the large surface area and also the localization of gallic acid on the fiber surface. The Ze-GA electrospun fibers are not cytotoxic and exhibited antimicrobial properties. Finally, heat-curing was postulated to modify the properties of zein electrospun fibers, such as to strengthen their structure and physical properties. Consequently, the colour properties, thermo-mechanical properties, surface hydrophobicity, morphology, release performance, molecular weight distribution, chemical interactions and structural properties of the heat-cured electrospun fiber mats were evaluated. An improved morphological stability of Ze-GA fibers was observed after immersion in water at 23 °C for 6 hr. All the electrospun fiber mats exhibited characteristic of α–helix rich protein. Overall, electrospinning has proven to be a versatile and promising approach that is capable of generating functionalized nanofibers suitable for food applications.