Green Extraction Techniques for Obtaining Bioactive Compounds from Mandarin Peel (<i>Citrus unshiu</i> var. <i>Kuno</i>): Phytochemical Analysis and Process Optimization

• Main Authors: Silvija Šafranko, Ina Ćorković, Igor Jerković, Martina Jakovljević, Krunoslav Aladić, Drago Šubarić, Stela Jokić
• Format: Article
• Language: English
• Published: MDPI AG 2021-05-01
• Series: Foods
• Subjects: mandarin peel; green extraction; bioactive compounds; bioflavonoids; volatile compounds
• Online Access: https://www.mdpi.com/2304-8158/10/5/1043

In this study, an efficient utilization and valorization of mandarin peel (<i>Citrus unshiu</i> Marc. var. <i>Kuno</i>) was investigated using innovative and green extraction techniques. The first step of this study included the extraction and analysis of the volatile compounds by performing a supercritical CO₂ (SC-CO₂) extraction under different operating pressure conditions (100 and 300 bar). The analysis of volatile compounds of the obtained extracts was conducted by gas chromatography-mass spectrometry (GC-MS), and limonene was found to be the dominant volatile component (13.16% at 100 bar; 30.65% at 300 bar). After SC-CO₂ treatment, the exhausted citrus peel waste enriched with bioactive compounds was subjected to subcritical water extraction (SWE) in a wide temperature range (130–220 °C) using different solvent-solid ratio (10–30 mL/g) in time periods from 5 to 15 min, in order to obtain bioflavonoids. Identification and quantification of present bioflavonoids was conducted by high-performance liquid chromatography with a with a diode array detector (HPLC), and hesperidin (0.16–15.07 mg/g) was determined as the most abundant flavanon in mandarin peel with other polyphenolic compounds that were possible by-products of thermal degradation. At higher temperatures, the presence of 5-hydroxymethylfurfural (5-HMF) and chlorogenic acid were detected. Antiradical activity and total phenolic content in the extracts were determined using spectrophotometric methods, while the process optimization was performed by response surface methodology (RSM).