Effects of solvent and n-3 rich fish oil on physicochemical properties of electrospun zein fibres

The omega-3 polyunsaturated fatty acids have been linked to the prevention of cardiovascular and cerebrovascular malaises. However, due to their susceptibility to oxidation and strong flavor, the use of these fatty acids remains a hurdle in food and nutraceutical applications. In this study, an electrospinning method was developed to encapsulate fish oil, up to 30% (w/w), in zein fibres. The effects of aqueous ethanol and isopropanol solvents on the solubility of zein, as well as the viscosity, conductivity, and surface tension of the polymer solutions, were investigated. Polymer solutions prepared in both solvents exhibited shear-thinning behaviour, where the ethanolic solutions had higher apparent viscosities for all treatments in comparison to isopropanol based solutions. Furthermore, electrical conductivity decreased significantly (p < 0.05) as the loading concentration of fish oil increased in the zein solutions. Scanning electron microscopy revealed that the electrospun zein fibres prepared from 70% (w/w) ethanol produced ribbon-shaped morphologies, while those prepared from isopropanol solvent resulted in beaded fibres. Moreover, the average diameter of these fibres increased in proportion to the fish oil loading. Attenuated total reflection-Fourier transform infrared spectroscopy analyses on the electrospun zein fibres showed that the aqueous ethanol solvent and the addition of fish oil promoted the formation of alpha-helix protein secondary structure while the isopropanol promoted the formation of intermolecular and intramolecular beta-sheet protein structure. Effects of polymer solution properties on the electrospun fibres and the potential practical applications of these ultrathin zein fibres were discussed. (C) 2014 Elsevier Ltd. All rights reserved.