Green Extraction of Essential Oils, Polyphenols, and Pectins from Orange Peel Employing Solar Energy: Toward a Zero-Waste Biorefinery

Following a rising demand for both environmentally friendly technologies and bioactive compounds, this study aims to develop a biorefinery concept that uses solar radiation instead of fossil source derived energies to extract essential oils, pectin, and polyphenols from orange peels. A hydro-distillation system has been used for extraction of volatile (essential oils) and nonvolatile (polyphenols and pectins) compounds using solar or conventional fossil energy. It was found that the essential oil quality and yield were similar; however, the extraction time was 36.8% higher for the conventional procedure. Total polyphenol content (TPC) and total flavonoid content (TFC) analysis of orange peels, extracted by solar or conventional fossil energy, showed that a higher amount of polyphenol and flavonoid compounds were preserved when solar energy was applied. Indeed, 75% of the TPC and 70% of the TFC after conventional and 77% of the TPC and 77.8% of the TFC, respectively, after solar extraction were still found in the orange peels. Analysis of narirutin and hesperidin, the main flavonoids present in citrus species, showed that both flavanones were not entirely solubilized in the distillation water. Similar results were observed after pectin extraction since most of it was preserved in the peels after essential oil extraction.