Effects of microwave heating on electrospinning of carob bean flour based nanofibers

Thesis Type: Postgraduate

Institution Of The Thesis: Middle East Technical University, Graduate School of Natural and Applied Sciences, Turkey

Approval Date: 2019

Thesis Language: English


Principal Supervisor (For Co-Supervisor Theses): Servet Gülüm Şümnü

Co-Supervisor: Serpil Şahin


In addition to time and energy saving advantages, microwave heating has some effects on functional properties of flours, especially starch and protein compounds. The aim of this study was to determine the effects of microwave pretreatment on physicochemical characteristics of carob flour and rice starch-based nanofibers produced by electrospinning. In addition, the effects of carob flour concentration (3%, 5% w/v) and rice starch addition (0.5% w/v) on nanofiber production were studied. Solutions were heated conventionally or by using microwave until 80°C is reached. In electrospinning process, 0.8 mL/h flow rate and 12 kV voltage were set constant. Scanning electron microscopy (SEM), water vapor permeability (WVP), X-Ray diffraction (XRD), mechanical test, differential scanning calorimeter (DSC), Fourier-transform infrared spectroscopy (FTIR) analysis were performed on the film samples. It was possible to obtain homogenous and bead free fibers when microwave heating was used. Nanofibers originated from microwave heated solution presented better characteristics in terms of water vapor permeability and mechanical properties as compared to conventionally heated one at the same concentration. While microwave heated sample had 1.68×10-12 g s-1m-1Pa-1 water vapor permeability value, conventionally heated sample had 2.13×10-12 g s-1m-1Pa-1 at 3% carob flour and 0.5% rice starch concentration. In the study, solution characteristics were investigated in terms of analysis of rheological properties, electrical conductivity and free amino group determination. It was found that microwave heated solution had higher viscosity value and free amino group amount as compared to conventionally heated solution at the same concentration. This study showed that microwave heating can be considered as a promising and more advantageous method for the preparation of electrospinning solutions rather than conventional heating.