ORIGINAL PAPER Visible and near-infrared absorption spectroscopy by an integrating sphere and optical fibers for quantifying and discriminating the adulteration of extra virgin olive oil from Tuscany Anna Grazia Mignani & Leonardo Ciaccheri & Heidi Ottevaere & Hugo Thienpont & Lanfranco Conte & Milena Marega & Angelo Cichelli & Cristina Attilio & Antonio Cimato Received: 2 August 2010 / Revised: 29 October 2010 / Accepted: 2 November 2010 / Published online: 24 November 2010 # Springer-Verlag 2010 Abstract Because of its high price, extra virgin olive oil is frequently targeted for adulteration with lower quality oils. This paper presents an innovative optical technique capable of quantifying and discriminating the adulteration of extra virgin olive oil caused by lower-grade olive oils. An original set-up for diffuse-light absorption spectroscopy in the wide 400–1,700 nm spectral range was experimented. It made use of an integrating sphere containing the oil sample and of optical fibers for illumination and detection; it provided intrinsically scattering-free absorption spectrosco- py measurements. This set-up was used to collect spectro- scopic fingerprints of authentic extra virgin olive oils from the Italian Tuscany region, adulterated by different concentrations of olive-pomace oil, refined olive oil, deodorized olive oil, and refined olive-pomace oil. Then, a straightforward multivariate processing of spectroscopic data based on principal component analysis and linear discriminant analysis was applied which was successfully capable of predicting the fraction of adulterant in the mixture, and of discriminating its type. The results achieved by means of optical spectroscopy were compared with the analysis of fatty acids, which was carried out by standard gas chromatography. Keywords Extra virgin olive oil . Absorption spectroscopy . Integrating cavity . Optical fibers . Adulteration . Chemometrics Protecting the authentic extra virgin olive oil Extra virgin olive oil (EVOO) is the only vegetable oil that is consumed as it is—freshly extracted from the fruit. Thanks to its balanced taste and flavored aroma, EVOO is capable of enhancing the most popular gastronomic recipes and is thus considered the chef ’ s gold. EVOO also offers highly beneficial health effects, thanks to both its high content of monounsaturated fatty acids, vitamins, and polyphenols—the antioxidant substances. EVOO extraction, being carried out by mechanical means only, preserves the contents of antioxidant com- pounds. Some of these molecules are not contained in other vegetable oils (e.g. polyphenols), or are removed by refining, while those that are contained in every vegetable oil (tocopherols) are partially removed by refining. Seed A. G. Mignani : L. Ciaccheri (*) CNR-IFAC, Via Madonna del Piano, 10-Building B, 50019 Sesto Fiorentino, FI, Italy e-mail: l.ciaccheri@ifac.cnr.it H. Ottevaere : H. Thienpont Vrije Universiteit Brussel, B-PHOT, Pleinlaan, 2, 1050 Brussels, Belgium L. Conte : M. Marega Università degli Studi di Udine, Dipartimento di Scienze degli Alimenti, Via Sondrio, 2A, 33100 Udine, Italy A. Cichelli Università degli Studi “G. D’Annunzio”, DASTA, Viale Pindaro, 42, 65127 Pescara, Italy C. Attilio : A. Cimato CNR-IVALSA, Via Madonna del Piano, 10-Building D, 50019 Sesto Fiorentino, FI, Italy Anal Bioanal Chem (2011) 399:1315–1324 DOI 10.1007/s00216-010-4408-y