Optimization of Focused Ultrasound Extraction (FUSE) and Supercritical Fluid Extraction (SFE) of Citrus Peel Volatile Oils and Antioxidants

In order to evaluate the use of citrus peel as a potential source of volatile oils and antioxidants in food industry, supercritical fluid extraction (SFE) and focused ultrasound extraction (FUSE) techniques have been thoroughly studied. Based on experimental designs and considering the extraction of monoterpenes among the volatile oils, the total phenol content, and the antioxidants, the most adequate extraction conditions have been defined for lemon and then applied to other citrus. The optimum SFE conditions for volatile oils and antioxidants were the following: pressure, 100 and 170 bar; temperature, 35 A degrees C for both; flow, 1 mL/min in both cases; EtOH%, 0 and 40 %, respectively. FUSE extraction of the volatile oils was carried out with cyclohexane and the antioxidants with ethanol. The optimum instrumental conditions were roughly the same (extraction time 5 min, cycles 5 s(-1), and amplitude 30 % in both cases, and 10 and 15 mL, respectively, in the case of solvent volumes). Based on successive extractions, FUSE revealed a more efficient technique owing to the solvent features. Finally, a stability test of the content of aromas and antioxidant capacity was carried out and aromas were stable stored at 4 A degrees C for 6 weeks and the antioxidant capacity, in the same conditions, for 13 weeks.