Composite pullulan-whey protein nanofibers made by electrospinning: Impact of process parameters on fiber morphology and physical properties

Novel electrospun fibers from different blends of whey protein isolate (WPI) and pullulan have been developed and characterized. The effect of the blend ratios on the solution properties, such as viscosity, surface tension and electrical conductivity, and morphology of the resulting electrospun structures were investigated. The addition of pullulan in the blends resulted in increased viscosity and lower conductivity of the solutions which were beneficial to form more uniform nanofibers with diameters of around 231 nm. Moreover, the influence of the processing parameters such as flow rate, applied voltage, tip-to-collector distance on the morphology of electrospun fibers were studied. The fiber diameter increased as the flow rate augmented while the effect of this parameter diminished when the solution viscosity was low. On the other hand, applied voltage and tip-to-collector distance did not have excessive influence on the size of the nanofibers. Therefore, solution properties have been identified as the most significant parameters in the electrospinning process using such hydrocolloid blends. Infrared spectroscopy indicated that the composite fibers exhibited spectral features of both polymeric components as well as pointed to intermolecular interactions between the polymeric species. The thermal stability of the fibers was better than that of pure WPI, while the calorimetrically determined glass transition temperature (Tg) decreased with increasing pullulan content in the biopolymer blend. Such composite materials may find use in the food and pharmaceutical industries in formulating new products with specific material properties. (C) 2017 Elsevier Ltd. All rights reserved.