Extraction and Analysis of Aroma Components from Four Types of Citrus Peels

The peels of citrus fruits are a valuable source of natural fragrances. However, due to extraction difficulties and the complexity of their chemical components, these natural fragrances are relatively rarely applied in skincare products. In this study, essential oils from the peels of four citrus varieties—Pomelo, Shatang Mandarin, Baba Mandarin, and Sweet Orange—were successfully extracted using steam distillation to investigate their characteristic aroma components. The chemical structures of these volatile organic compounds were identified and comparatively analyzed using Gas Chromatography-Mass Spectrometry (GC-MS). By examining structural features, the relationships between the molecular structures of the aroma compounds and their specific scents were discussed. GC-MS analysis revealed that the content of D-limonene in Shatang Mandarin peel essential oil reached up to 82.3%, whereas in Pomelo peel essential oil, it was only 57.5%. Conversely, the content of γ-terpinene in Pomelo oil was unexpectedly high at 13.2%. Furthermore, the Pomelo peel extract contained unique components such as δ-elemene, germacrene D, and nootkatone, which are sesquiterpenes and sesquiterpene ketones. Because these components possess cyclic structures and relatively large molecular weights, their volatility is reduced, endowing the Pomelo essential oil with a much more long-lasting aroma. Finally, these natural organic fragrances were incorporated into homemade cleansing mousses, and user acceptance was evaluated through a questionnaire. Results indicated that Pomelo peel extract achieved the highest public acceptance due to its pure, fresh, and richly layered scent, making it the optimal natural fragrance ingredient for skincare.