The Effect of Drying Condition on Citrus sinensis (Osbek) Peel Waste Essential Oil's Composition, Antioxidant, Antibacterial and Tyrosinase Inhibition Activities

Orange peel waste (OPW) is a source of functional ingredients including essential oils (EOs). This coproduct has a seasonal production and is perishable due to its high moisture content. Drying could be an efficient method to conserve OPW for furthers uses. The aim of this work is to investigate the effect of five different drying conditions including: lyophylisation, shade drying, oven drying (50, 60 and 70 C-degrees) on the composition, antibacterial, antioxidant and tyrosinase inhibition activities of OPW EOs. Our results showed that drying time were signifcantly affected by OPW drying conditions. Indeed, the shortest drying times were recorded in the OPW dried in the oven at temperatures of 60 C-degrees (24 H) and 70 C-degrees (26 H). Drying conditions affected significantly the yield of OPW on EOs: fresh OPW had the highest yield (0.98 +/- 0.1%). The chemical composition of OPW EOs was, also modified by the drying condition. However, Limonen stills the major compound, in all the tested EOs. Antibacterial activity of the tested EOs, depended in both bacteria and EOs. Indeed, the largest inhibition diameter and the lowest MIC was recorded in E.coli when treated with shade dried OPW EO. For the inhibition of initial bacteria cell attachment, our results showed that it ranged between 3.42 +/- 0.03% and 61.13 +/- 0.0.04% recorded respectively in E. coli when treated with oven dried OPW EO at 50 C-degrees and in P. aeruginosa when treated with shade dried OPW EO. The inhibition percent of biofilm formation and development varied between 0.19 +/- 0.02% and 51.29 +/- 0.08%, recorded respectively in P. aeruginosa and in S. typhimurium, when both of them are treated with oven dried OPW EO at 50(degrees)C. DPPH and ABTS test showed that, the highest antioxidant activity was found in EO extracted from fresh OPW and from OPW dried in the oven at 70 C-degrees. For the tyrosinase inhibition activity, results showed that the IC50 ranged between 12.66 +/- 0.66 mg/mL and 120.65 +/- 3.43 mg/mL, recorded in the EOs extracted respectively from OPW dried in the oven at 70 C-degrees and 50(degrees)C.