Effect of Second Cooling on the Chemical Components of Essential Oils from Orange Peel (Citrus sinensis)

A second cooling was added to the oil collectors of an improved Clevenger-type apparatus (ICT) to investigate the thermal reaction of essential oils from orange peel compared to a traditional Clevenger-type apparatus (CT). The results demonstrated the yield rate of essential oil from ICT was significantly higher (p < 0.05) than that from CT. The major components of the essential oils consisted of monoterpenes, such as d-limonene, β-myrcene, β-pinene, γ-terpinene, α-pinene. Interestingly, ICT prevented the thermal reaction—the transformation of β-myrcene to β-thujene—and reduced the oxidation on α-pinene and β-pinene of the essential oil in comparison to CT. In addition, the yield rate of γ-terpinene can also be improved via ICT compared to CT. Thus, ICT is an effective improvement to traditional CT.