Headspace Solid-Phase Microextraction–Gas Chromatography–Mass Spectrometry Quantification of the Volatile Profile of More than 1200 Virgin Olive Oils for Supporting the Panel Test in Their Classification: Comparison of Different Chemometric Approaches

Abstract

A reliable and robust tool for supporting the panel test in virgin olive oil classification is still required. We propose four chemometric approaches based on t test, principal component analysis (PCA) and linear discriminant analysis (LDA), applied for combining sensorial data, and chemical measurements. The former was from the panel test, and the latter was from headspace solid-phase microextraction–gas chromatography–mass spectrometry quantitation of 73 volatile organic compounds (VOCs) of 1223 typical commercial virgin olive oils, with most of them recognized as difficult to classify with accuracy by the panel test. The approaches were developed and validated, and the best results, with 83.5% correct classification, were using the PCA–LDA approach. Among the other methods, developed for proposing simplified procedures based on a smaller number of VOCs, the best method gave 80.1% correct classification only using 10 VOCs. All of the approaches suggested that octane, heptanal, pent-1-en-3-ol, Z-3-hexenal, nonanal, and 4-ethylphenol should be considered as a basis of volatiles for classification of olive oil samples.

Supporting the Sensory Panel to Grade Virgin Olive Oils: An In-House-Validated Screening Tool by Volatile Fingerprinting and Chemometrics

“…Therefore, considering that the uncertain samples would be assessed by the sensory panel and would be correctly graded, we can state that a mean reliable assignment of 84% would be reached by combining the instrumental screening tool and the panel evaluation, with a panel workload reduction to one-third of the total sampling. Therefore, the classification rate obtained by the present strategy is comparable to those obtained by other approaches [ 11 , 12 , 13 , 15 , 16 , 21 ], but it is based on a simple, relatively fast, automatable and widespread technique.…”

“…Generally, volatile organic compounds (VOC) are the most pursued markers, due to their widely reported relationship with the sensory properties of virgin olive oil [ 8 , 9 , 10 ]. Their analysis has been performed by different methods, such as (i) gas chromatography–mass spectrometry (GC–MS) [ 11 , 12 , 13 , 14 ], (ii) gas chromatography–ion mobility spectrometry (GC–IMS) [ 15 , 16 , 17 , 18 , 19 ], (iii) proton transfer reaction–time of flight-mass spectrometry (PTR–ToF-MS) [ 4 , 20 ] and (iv) MS without a previous separation step [ 21 , 22 , 23 , 24 ]. Rapid methods like flash gas chromatography (FGC) electronic nose have also been used for this purpose [ 25 , 26 ].…”

“…In this sense, in a preliminary work [ 14 ], we presented a proof of concept for an instrumental screening tool based on virgin olive oil volatile fingerprinting by head space-solid phase micro extraction (HS-SPME) and GC–MS analysis. This analytical method is known to be simple, relatively fast, automatable, affordable and highly sensitive [ 13 , 29 , 30 , 31 ]. Besides, that analytical tool is based on the use of raw chromatographic data, also called fingerprint, an approach that allows working with the full analytical information of samples, increasing the amount of information used in modelling as well as overcoming the identification and integration troubles of the conventional target approach [ 32 ].…”

Tracking Sensory Characteristics of Virgin Olive Oils During Storage: Interpretation of Their Changes from a Multiparametric Perspective

“…These compounds show that VOO1 and VOO3 underwent a decrease in the concentration of the majority of the selected compounds, which have pleasant attributes, such as (E)-3-hexen-1-ol, which explains the loss of their initial positive attributes (median of the fruity attribute) during the storage (Figure 2). Sample VOO3 showed a large increase of the concentration of heptanal and (E)-2-heptenal, which are related to oily and oxidized aroma descriptors [1,31,35]. Finally, VOO2 and VOO4 were in an advanced oxidation state at the end of the storage, as it is pointed out by the increase of the content of the volatiles related to the rancid defect [36], such as nonanal, heptanal and hexanoic acid.…”

Flash Gas Chromatography in Tandem with Chemometrics: A Rapid Screening Tool for Quality Grades of Virgin Olive Oils

“…Recently, different analytical techniques combined with chemometric statistical approaches have been proposed to predict sensory information [7][8][9].…”