Comparison of Characteristics of Oils Extracted from a Mixture of Citrus Seeds and Peels Using Hexane and Supercritical Carbon Dioxide

The processing of citrus fruits into juice is one of the world's largest processing industries. The by-products of this industry are about 50 % of the raw processed fruit. This not only wastes a resource of potential value, but also causes disposal problems. The aim of this work was to study the characteristics of oils extracted from a mixture (MX) of citrus seeds (CS) and citrus peels (CP) using hexane and supercritical carbon dioxide (SC-CO2) so that those by-products can be valorized effectively. The SC-CO2 extraction conditions were 45 and 60 A degrees C, 200 and 250 bar while for hexane was 70 degrees C. Hexane showed significantly (P < 0.05) higher yield than SC-CO2. The chemical composition was analyzed by GC-MS and phytosterols, monoterpenes, sesquiterpenes and oxygenated monoterpenes were the main compounds of the oils. The fatty acid composition was determined by GC and linoleic acid was the major fatty acid. The oxidative stability (OS) was performed by Rancimat and the hexane extracted oils showed higher OS. The antioxidant activity was tested with DPPH and ABTS assay and SC-CO2 extracted oils showed higher activity with IC50 values of 3.86 and 4.00 mg/ml respectively for MX and CP oils. Antimicrobial activity was tested for both extracted oils against gram positive and gram negative bacteria with SC-CO2 extracted oils exhibiting better inhibition. From this study, we can say that the citrus by-products can be valorized by combining CS and CP which could give the oils with potentiality to be used in many applications.