Effect of Nonionic Surfactants on the Oxidation of Lemon Oil

The oxidative effects of sorbitan esters on lemon oil and γ-terpinene in emulsion and solubilization were investigated. The oxidation was followed by gas chromatography (GC) and peroxide value (POV). The determination of the site of γ-terpinene within micelles was made by ultraviolet spectro scopy (UV) and solubility measurement. The summary of the results is shown below. 1) The formation of p-cymene from γ-terpinene during deterioration of lemon oil was shown. 2) Sorbitan esters strongly inhibitted oxidative activities. 3) The monomolecular film of sorbitan esters appeared to inhibit the oxidation. 4) Lemon oil in the emulsion of O/W type did not oxidize, while in that of W/O type it did, 5) The site of γ-terpinene within the Tween 20 micelles was deep penetration of the palisade layer. 6) Suspended or emulsified γ-terpinene was oxidised at greater rate than solubilised γ-terpinene. Then, Tween 20 micelles were considered to inhibit the oxidation of γ-terpinene.