Abstract
The essential oils of various commercial citrus species were studied by ATR/FT-IR as well as NIR-FT Raman spectroscopy. Some of the most relevant monoterpene components occurring in the oil, such as limonene and γ-terpinene, show characteristic key bands in the IR and Raman spectra, which are useful for making a quantitative distinction between different oil types. Applying principal component analysis (PCA) to the spectral data, the individual citrus products are located, in most cases, as separated clusters in a 3-dimensional factor space. Cross-validation statistics showed that a partial least-square (PLS) algorithm was able to produce high quality predictions of the relative oil composition as well as general quality parameters. Both complementary spectroscopic techniques described in this study have the potential to replace existing analytical procedures because they are capable of faster quality control measurements and they allow on-line analyses during distillation or extraction processes to be performed.