Diffuse-light absorption spectroscopy and chemometrics for discrimination and quantification of extra virgin olive oil adulterants

Abstract

A selection of top-quality extra virgin olive oils with excellent nutraceutic properties was artificially adulterated by means of lower-grade olive oils commonly used in commercial counterfeits. The oil sample set was analyzed by means of diffuse-light absorption spectroscopy performed in the wide 400-1700 nm spectral range. A setup based on optical fiber technology was experimented, which made use of an optical fiber supercontinuum source. The spectroscopic library was processed by means of a Partial Least Squares regression for quantifying the adulterant concentration, followed by a Principal Component Analysis and Linear Discriminant Analysis for identifying the type of adulterant. I. PROTECTING EXTRA VIRGIN OLIVE OILExtra 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, besides containing the highest levels of antioxidants, has the highest amount of monounsaturated fatty acids. It is a "healing fat", since it controls the "bad" LDL cholesterol levels while raising the "good" HDL ones [1,2]. Studies have shown that people who consumed 25 ml (about 2 tablespoons) of EVOO daily for 1 week presented less oxidation of LDL cholesterol and higher levels of antioxidant compounds in the blood [3], and, more generally, that EVOO is a panacea of the entire cardiovascular system [4].Because of the time-consuming agronomical practices used for EVOO production, and the low production efficiencyfrequently lower than 20% as oil yield -the price of EVOO is high, especially compared with that of other vegetable oils. Consequently, EVOO is prone to adulteration with cheaper oils in order to increase profits. In addition to an economic burden, EVOO adulteration is detrimental if consumers react by buying other cooking fats or dressings, thinking that EVOO cannot be trusted. The negative implications on consumer confidence are even worse than the economic ones. Lastly, EVOO protection measures also imply the product area conservation, as far as landscape, tourism, and job preservation are concerned.While the European Commission regulations are indicating the characteristics of olive oil types, and are suggesting the methods of analysis [5], a lot of research is currently carried out, in order to experiment innovative techniques for authenticating extra virgin olive oils and predicting potential frauds.Numerous methodologies exist for EVOO authentication, both for adulteration detection and quantification.

A Spectroscopy-Based Approach for Automated Nondestructive Maturity Grading of Peach Fruits

“…high-resolution fiber-optic spectrometers, to retrieve fruit properties such as FF by suitable processing of the fruit reflectance spectra, thus avoiding fruit damage and waste and, in turn, allowing faster, repeated measures on each fruit of the batch. This nondestructive approach has recently been pursued in several other fields of food safety and control besides the fruit sector [13] [14] [15] [16] [17] [18] [19], as the wide availability of bright LED illuminators and portable and ultra-compact spectrometers, along with the desired properties inherent to optical fibers, enables implementation of low-cost compact instrumentation with great potential in this field [14] [15].…”