Design and preparation of isolated whey protein-polysaccharide based system using electrospinning and determination of its physicochemical and functional properties

Abstract

Background: Electrospinning is a simple, cost-effective, and versatile method to produce fibers and particles in the scale of micro and nanometers. In this method, nanofibers are produced by applying electrical field to a polymer solution. The fibers produced using this method have high surface-to-volume ratio and porosity which are used in various fields of medicine, smart drug delivery, and food industry. The aim of this study was to investigate the spinnability of a mixed solution of WPI and GG at different concentration ratios with regard to changes in the physicochemical properties of solutions. In this study, for the first time, whey protein isolate and guar gum were used to produce nanofibers. Curcumin was used to evaluate the performance of the nanofibers for the encapsulation. Materials and Methods: Guar gum was purified using an immersion technique in alcohol. Guar gum solution was prepared at different %wt. Whey protein isolate was added to guar gum solutions at different ratio. Mixture of water and acetic acid in a ratio of 90:10 was used as solvent. Nanofibers were produced from whey protein isolates and purified guar gums by determining the optimal parameters including (Polymeric solution parameters: viscosity, electrical conductivity, surface tension and technical parameters: voltage, needle gap to collector plate, solvent flow rate) in electrospinning. The morphology and the particle size were observed using a scanning electron microscopy (SEM). Viscosity, surface tension, and electrical conductivity of the solutions were measured. The best formulation in terms of morphology and Nano-fiber size were selected for further experiments. The chemical interactions were investigated by Fourier-transform infrared spectroscopy (FTIR) and Thermogravimetric Analysis (TGA). The encapsulation efficiency and the release rate of curcumin was measured using phosphate-buffer saline medium. Results: The protein solution acidified to pH=3.5 showed no spinnability at even high concentration (10% wt.), but with increasing of GG concentration from 0/7 to 0/8% wt. at fixed concentration of whey protein isolate a visible transformation was seen in the morphological appearance from the bead to the nanofibers at SEM images. The results showed that the solutions, containing 7, 9, and 12 %wt. of the whey protein isolate and 0.7, 0.8, and 0.9 %wt of the guar have the ability to be electrospun at a voltage of 20 kv, flow rate of 6/0 ml/min, and needle distance to collector plate of 8 cm. The optimum point in the production of Guar gum and whey Protein Isolate Nanofibers was in a concentration ratio of 0.7% Guar gum and 9% protein isolate. The optimum conditions were 20 kV, a flow rate of 0.6 ml / min and a needle distance to a collector plate of 8 cm. The optimum point in the production of Guar gum and whey Protein Isolate Nanofibers was in a concentration ratio of 0.7% Guar gum and 9% protein isolate. The optimum conditions were 20 kV, a flow rate of 0.6 ml / min and a needle distance to a collector plate of 8 cm The prepared nanofibers had the uniform morphology and diameters in the range of 190 to 900 nm. Electrospinning efficiency of WPI-GG solution was strongly influenced by concentration ratio of them and changes in the viscosity of GG solutions in the presence of different concentration of WPI. FTIR spectrum of GG: WPI blended nanofibers showed the formation of α-helical structure of WPI instead of intramolecular β-sheet structures of pure WPI. The encapsulation efficiency of curcumin was 91% and the amount of curcumin release was 75% during 24 hours. Conclusion: The whey protein isolate and purified guar gum solution mixtures showed spinnability to produce nanofibers. Moreover, curcumin is successfully encapsulated in these nanofibers.