Utilization of Pectin Produced from Infrared Dried Orange Peel in Development of Electrospun Nanofibers and Characterızation of the Nanofibers

Abstract

In recent years, utilization of infrared (IR; Infrared) drying in food industry is increasing, due to its advantages (efficient, energy saving, low cost, direct heat penetration, fast heating rate, short processing time) over conventional heating. Pectin has been used in many researches in food and pharmaceutical industries due to its biocompatibility, nontoxic structure and biodegradability. Pectin is also used in production of nanofiber by using electrospinning which has advantages (less energy requirement, better control of particle size, cost effectiveness, applicability at room temperature). Wastes of fruit juice industry are important sources of pectin. In this thesis, pectin was extracted from orange peels infrared dried or oven dried at different conditions. The effects of different drying and extraction conditions on pectin properties were investigated. Nanofibers were produced by using these pectin samples by itself or with PEO or PVA at different electrospinning parameters. The effects of pectin properties and different electrospinning parameters on the characteristics of nanofibers were investigated. Orange peel samples were infrared dried (600W,700W,800W for 30min) or oven dried (60°C,70°C). Pectin was extracted from dried orange peels at 90°C, by using different extraction conditions (pH1-1.5-2, for 60-90-120min.). Best pectin extraction method was determined by investigating properties of pectin samples and pectin nanofibers. The pectin samples had high purity (galacturonic acid 72.79-98.66%) and high esterification degree (59.22-94.06%). The highest yield of pectin was obtained at pH1-120min for oven dried and pH1.5-120min. for infrared dried samples. Pectin yield values together with the properties of electrospun nanofibers confirmed that pectin extraction at pH1.5-120min. is the key parameter for finest fiber formation with better morphology. It was not possible to produce nanofibers from pure pectin (extracted from orange peels infrared dried at 800W-30min.) solutions. Nanofibers were produced by using pectin:PEO (3:1, 3:2, 4:1, 4:2, 5:1% (w/w)) or pectin:PVA (2:5, 2:6, 2.5:5, 2.5:6, 3:5, 3:6% (w/w)) solutions in order to determine the co-polymer. Different electrospinning parameters such as flow rate (0.2-0.7ml/h), voltage (15-35kV), distance (8-20cm.) were used. Higher concentrations of pectin was used in pectin+PEO solutions as compared to pectin+PVA solutions. Morphology (SEM), DSC thermogram, water contact angle of the nanofibers were determined. Based on the results, the most appropriate polymer and electrospinning solution concentration was chosen as pectin:PEO 3:1(%w/w,with Triton X-100) and the best electrospinning parameters were chosen as 15cm,0.5ml/h,35kV. XRD patterns of PEO nanofibers showed that electrospinning process reduced the crystallinity of PEO. However, electrospinning did not cause a change in XRD patterns of pectin. Enthalpy values (89.31-108.95 J/g) of the pectin samples produced in the study were higher as compared to that of commercial pectin (71.07 J/g). Both of the peaks of PEO or pectin were observed in FTIR, DSC thermogram and XRD pattern for pectin+PEO nanofibers, indicating the compatibleness of PEO and pectin in nanofiber production. Pectin+PEO nanofibers including pectin produced in the study had higher water contact angle value (20.98-50.14°) as compared to that of commercial pectin (15.60°) nanofiber. Pectin extracted from orange peels dried at 700W-30min. showed moderate (50.14°) hydrophilic surface characteristics. Overall results indicated that pectin+PEO nanofibers may have a potential in various applications of food industry.