Pectin production from orange peels with deep eutectic solvents

In this study, pectin extraction was carried out from orange peels, which is a food industry waste, by using a deep eutectic solvent (DES) (choline chloride : formic acid). Pectin samples were obtained by maceration and microwave methods at different deep eutectic solvent concentrations (3, 5, and 8%) (v/v), different temperatures (70, 80, and 90 C), microwave powers (180, 360, and 540 W), and durations (2-90 min), and the effect of process parameters on pectin yields was investigated. In general, it has been determined that all process parameters have a positive effect on pectin yield. The highest pectin yield was determined as 46.09±0.6% and 40.0±0.3% for maceration (90 C, 8% DES, 60 min) and microwave (360 W, 8% DES, 15 min) methods, respectively. The galacturonic acid contents of the pectin samples obtained at optimal conditions with the highest yield were found as 22.25±0.5% and 29.50±4.7% for the maceration and microwave methods, respectively. In addition, pectin samples obtained by both methods could be classified high methoxyl pectin. Extraction methods with DES yielded pectin with a lower water holding capacity but higher solubility compared to conventional extraction. The viscosity values of the samples were determined as 3.58±0.048 and 5.69±0.074 mPa.s for the maceration and microwave methods, respectively. The highest total phenolic content (8.19±0.43 mg gallic acid/g pectin) was determined in the pectin sample obtained from the maceration-DES method. Also, the maceration-DES samples generally had a flat appearance; it was noted that the pectin samples obtained from the microwave-DES extraction method had a porous structure and some micro-fractures. In conclusion, the microwave-assisted-deep eutectic solvent method could be preferred in pectin extraction in the future since it provides high yields at a relatively short extraction time and it is environmentally friendly method.