Abstract
In order to differentiate the extra virgin olive oils (EVOO) of different origin of purchase, such as monovarietal Italian EVOO with protected denomination of origin (PDO) and commercial-blended EVOO purchased in supermarkets, a number of samples was subjected to the analysis of volatile aroma compounds by both targeted gas chromatography/mass spectrometry (GC-MS) and untargeted profiling by comprehensive two-dimensional gas chromatography/mass spectrometry (GC×GC-TOF-MS), analysis of phenols by targeted high-performance liquid chromatography/mass spectrometry (HPLC-DAD-ESI/MS), and quantitative descriptive sensory analysis. Monovarietal PDO EVOOs were characterized by notably higher amounts of positive LOX-derived C6 and C5 volatile compounds, which corresponded to the higher intensities of all the assessed positive fruity and green odor sensory attributes. Commercial-blended EVOOs had larger quantities of generally undesirable esters, alcohols, acids, and aldehydes, which coincided with the occurrence of sensory defects in many samples. Many minor volatile compounds that were identified by GC×GC-TOF-MS were found to differentiate each of the two investigated groups. The differences between the groups with respect to phenols and taste characteristics were evident, but less pronounced. The results that were obtained in this study have undoubtedly confirmed the existence of the large heterogeneity of oils that are sold declared as EVOO. It was shown that GC-MS, GC×GC-TOF-MS, and HPLC-DAD-ESI/MS analyses have complementary outputs, and that their use in combination has advantages in supporting the results of sensory analysis and objectively differentiating these groups of EVOO.
Highlights
During the previous few decades, the olive oil scientific community and industry have become increasingly linked by the common goal of improving olive oil production and quality [1]
The chemical parameters that are not regulated by the legislation, but they are certainly among the most meaningful for evaluating and understanding extra virgin olive oil (EVOO) sensory and nutritional quality and they could serve as differentiators that are based on such criteria, are volatile aroma compounds and phenols [7,8,9]
The combined use of gas chromatography/mass spectrometry (GC-MS) and GC×GC-TOF-MS analysis for volatile aroma compounds proved to be a powerful analytical option, providing broad coverage of the volatilome, which is useful for the differentiation of the two classes of EVOO with respect to the origin of purchase: monovarietal protected denomination of origin (PDO)
Summary
During the previous few decades, the olive oil scientific community and industry have become increasingly linked by the common goal of improving olive oil production and quality [1]. The consumers are often unaware of the great heterogeneity with respect to sensory and nutritional quality of oils within the category of the highest quality grade (EVOO), which is mostly present because the thresholds that are set by the European Commission regulation (EEC, 1991) for chemical parameters (acidity, peroxide value, K232 , K270 , ∆K values, alkyl esters) are not rigorous and they can be met relatively while the prescribed sensory analysis method practically only discriminates oils with certain fruitiness (median > 0) and without sensory defects from the defective ones [3]. Rather different products comply with the requirements of the EVOO category, which often confuses the consumers, especially when it comes down to the large span of EVOO prices [4]. The typical fruity and green aroma of high quality EVOO mainly consists of C5 and C6 aldehydes and ketones, enzymatically formed by lipoxygenase (LOX)
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