The Effects of Microwave and Oven Drying on Bioactive Compounds Individual Phenolic Constituents and the Fatty Acid Profiles of Bitter Orange, Mandarin and Grapefruit Peel and Oils

Abstract: In this study, the effects of oven and microwave drying techniques on antioxidant capacity values, total phenol, carotenoid, flavonoid results, fatty acids, and individual phenolic constituents of bitter orange, mandarin and grapefruit peels were investigated. Total phenolic amounts of bitter orange, mandarin and grapefruit peels dried were measured between 627.21 (70 °C) and 1280.03 mg GAE/100 g (control), 485.50 (900 W) and 991.39 mg GAE/100 g (control) and 393.03 (100 °C) and 847.04 mg GAE/100 g (control), respectively. The catechin contents of fresh (control) and dried bitter orange and mandarin peels were identified to be between 174.29 (100 °C) and 527.54 mg/100 g (control) to 160.02 (control) and 255.46 mg/100 g (70 °C), respectively. Also, the catechin amounts of grapefruit peels varied between 177.72 (70 °C) and 446.75 mg/100 g (control). Rutin contents of bitter orange peel changed between 48.84 (540 W) and 380.20 mg/100 g (control). Oleic acid results of bitter orange, mandarin and grapefruit peel oils were identified to be between 20.26 (control) and 49.82% (70 °C), 7.64 (control) and 53.46% (70 °C) and 40.25% (control) and 50.30% (70 °C), respectively. While linoleic acid values of bitter orange peel oils are recorded between 17.08 (70 °C) and 30.46% (control), the linoleic acid results of mandarin and grape fruit peel oils were identified to be between 18.23 (70 °C) and 35.55% (control) to18.05 (70 °C) and 29.28% (control), respectively. Graphical Abstract: (Figure presented.)