Encapsulation for the food and pharmaceutical industries has been with us for many years – new immobilization methods, new carrier materials and different methods for releasing functional molecules have all entered the research field (Gibbs et al.,, 1999). Electrospinning of fibres is one of those newer technologies and we review some of its properties here but there are some excellent reviews on various food applications (Bhushani & Anabdharamakrishnan, 2014).
The technology of electrospinning has been with us for only a few years but its received new impetus in the light of creating new food products. Besides creating foods which we are all familiar like the modern versions of candy floss, electrospun fibers are a safe delivery vehicle for probiotics, nutrients and vitamins (Katouzian & Jafari, 2016). It is even possible to create ‘meat’ using vegetable food materials when the technique is employed. As well as food, the technology produces fibres for other types of delivery systems, for oil recovery, protective clothing ( Fathi, 2015; Bhardwaj & Kundu, 2010), medical devices and membrane filtration (Alazab et al., 2017).
Characteristics Of Electrospun Fibers
Electrospun fibres look like nonwoven ultrafine fibre with diameters of between several tens to several hundred nanometers. They are formed by applying a high-voltage electric field to a solution containing polymers (Teo and Ramakrishna, 2006). The technology shares similarities with electrospraying and the older more conventional technologies of dry spinning fibres. There is no need for high temperatures in the production of the fibres which means highly complex polymers can be used and encapsulated materials are not damaged during processing.
Unique Properties Of Electrospun Fibres
The nanofibers not only have tiny diameters but have other advantages such as a high porosity with very small pore size so offering a large surface area-to-volume ratio (Kong & Ziegler, 2014). Other benefits include a high gas permeability (Okutan et al., 2014). Electrospinning also appears to improve the mechanical properties of the polymer including stiffness and tensile strength.
Polymers Used In Applications
Typical edible food polymers have all been tested with electrospinning. We can find numerous examples in the literature. Zein prolamine – a protein, soy protein and whey protein have all been electrospun as have starches. All these fibre sources are sustainable agroploymers and are successfully exploited because of their low cost and availability.
Encapsulated materials include β-carotene which is normally light sensitive and not very photostable but which is protected to a certain extent in electrospun fibres. In this example, zein prolamine was employed. The fiber capsules were sized in both the micro- and nano ranges. The encapsulation process preserved the fluorescence of these polyene molecules according to observations with confocal Raman imaging spectroscopy. In this example, the antioxidant properties were retained and uniformly dispersed inside the zein fibres (Fernandez et al., 2009).
Antioxidants like gallic acid have been incorporated into zein ultra-fine fibres. The properties were assessed using X-ray diffraction (XRD) and differential scanning calorimetry (DSC); and the interaction between gallic acid and zein was attested to by attenuated total reflection-Fourier transform infrared (ATR-FTIR) (Neo et al., 2013).
It’s possible to construct hybrid encapsulation structures. Again, carotene has been loaded into nanoliposomes which have then been incorporated into polymeric ultrathin fibres. The development of hybrid structures means their water solubility is improved and so hydrophobic, oily based ingredients can be incorporated successfully. It implies that light sensitive added-value food components can be preserved using this method.
Starches are good materials for encapsulation. They dissolve in hot water and then form a quick paste when cooled. Various types of electrospun fibres are created from starches because so many different types of paste compositions can be produced.
Proteins make fine electrospun fibres produced from both plant as well as animal sources. Gelatin, derived from animal collagen as well as zein from wheat which is a plant protein. Zein is soluble in water/ethanol mixtures while gelatin is water soluble.
What other food ingredients have been tried ? Fish oil (Garcia-Moreno et al., 2016) dispersed as small droplets in another nanofiber type, poly(vinyl alcohol) (PVA).
Alazab, M., Mitchell, G. R., Davis, F. J., & Mohan, S. D. (2017). Sustainable electrospinning of nanoscale fibres. Procedia Manufacturing, 12, pp. 66-78
Bhardwaj, N., Kundu, S.C. (2010) Electrospinning: a fascinating fiber fabrication technique. Biotechnol. Adv. 28 (3) pp. 325–347
Bhushani, J. A., & Anandharamakrishnan, C. (2014). Electrospinning and electrospraying techniques: Potential food based applications. Trends in Food Science & Technology, 38(1), pp. 21-33.
Fathi, M. (2015) Nano-Delivery system for development of functional food: production, application and trends, in: G.N. Govil (Ed.), Nutraceuticals and Functional Food, Studium Press, pp. 270–288.
Fernandez, A., Torres-Giner, S., & Lagaron, J. M. (2009). Novel route to stabilization of bioactive antioxidants by encapsulation in electrospun fibers of zein prolamine. Food Hydrocolloids, 23(5), pp.1427-1432. https://doi.org/10.1016/j.foodhyd.2008.10.011
García-Moreno, P. J., Stephansen, K., van der Kruijs, J., Guadix, A., Guadix, E. M., Chronakis, I. S., & Jacobsen, C. (2016). Encapsulation of fish oil in nanofibers by emulsion electrospinning: Physical characterization and oxidative stability. Journal of Food Engineering, 183, pp. 39-49. https://doi.org/10.1016/j.jfoodeng.2016.03.015
Gibbs, B.G., Kermasha, S., Alli, I., Mulligan, C.N. (1999) Encapsulation in food industry: a review. Int. J. Food Sci. Nutr. 50 pp. 213–24
Katouzian, I., Jafari, S.M. (2016) Nano-encapsulation as a promising approach for targeted delivery and controlled release of vitamins. Trends Food Sci. Technol. 53 (2016) pp. 34–48
Kong, L., & Ziegler, G. R. (2014). Fabrication of pure starch fibers by electrospinning. Food Hydrocolloids, 36, pp. 20-25.
Neo, Y.P., (2013) Encapsulation of food grade antioxidant in natural biopolymer by electrospinning technique: A physicochemical study based on zein–gallic acid system. https://doi.org/10.1016/j.foodchem.2012.09.010
Okutan, N., Terzi, P., & Altay, F. (2014). Affecting parameters on electrospinning process and characterization of electrospun gelatin nanofibers. Food Hydrocolloids, 39, pp. 19-26.
Teo, W.E., Ramakrishna, S. (2006) A review on electrospinning design and nanofibre assemblies. Nanotechnology 17: R89–R106.