Validation of SPME-GCMS method for the analysis of virgin olive oil volatiles responsible for sensory defects

Exploring the Connection between the Occurrence and Intensity of "Grubby" Defect and Volatile Composition of Olive Oil

In order to investigate the relationship between the occurrence of the "grubby" sensory defect caused by olive fruit fly (Bactrocera oleae (Rossi)) infestation and the resulting volatile composition, virgin olive oils were extracted from olives of the Leccino cultivar with 0%, 50%, and 100% olive fly infestations and subjected to analysis of the basic chemical quality parameters, fatty acids and volatiles, and sensory analysis by the Panel test. A 100% olive fly infestation reduced the basic chemical quality of the oil, while the fatty acid composition was not affected in any case. The overall sensory quality score and intensity of the positive sensory attributes decreased, while the intensity of the "grubby" defect increased proportionally to the degree of infestation. The occurrence and intensity of this defect were clearly causally related to the concentrations of 3-methylbutanal, 2-methylbutanal, β-ocimene, ethyl 2-methylbutyrate, dimethyl sulfoxide, 4-methyl-5H-furan-2-one, α-farnesene, 6-methyl-5-hepten-2-one, 1-octanol, E-2-nonen-1-ol, benzeneacetaldehyde, heptanal, and octanal, implying that the perception of "grubby" comes from their joint contribution to the overall olive oil flavour. In addition to contributing to the understanding of the chemical origin of "grubby", the results obtained could potentially be used to develop strategies to support sensory analysis in the classification of olive oil quality and the confirmation of the presence of this sensory defect in oil samples.

Determination of adulteration, geographical origins, and species of food by mass spectrometry

Food adulteration, mislabeling, and fraud, are rising global issues. Therefore, a number of precise and reliable analytical instruments and approaches have been proposed to ensure the authenticity and accurate labeling of food and food products by confirming that the constituents of foodstuffs are of the kind and quality claimed by the seller and manufacturer. Traditional techniques (e.g., genomics-based methods) are still in use; however, emerging approaches like mass spectrometry (MS)-based technologies are being actively developed to supplement or supersede current methods for authentication of a variety of food commodities and products. This review provides a critical assessment of recent advances in food authentication, including MS-based metabolomics, proteomics and other approaches.

Characterization of Olive Oil Volatile Compounds after Elution through Selected Bleaching Materials-Gas Chromatography-Mass Spectrometry Analysis

Using different bleaching materials to eliminate or reduce organic volatiles in deteriorated olive oils will positively affect its characteristics. This study aims to identify the volatiles of oxidized olive oil after physical bleaching using selected immobilized adsorbents. Oxidized olive oil was eluted using open-column chromatography packed with silica gel, bentonite, resin, Arabic gum, and charcoal at a 1:5 eluent system (w/v, adsorbent: oxidized olive oil). The smoke point was determined. The collected distilled vapor was injected into GC-MS to identify the volatiles eluted after partial refining with each of these bleaching compounds. The results showed that volatile compounds were quantitatively and qualitatively affected by the type of adsorbents used for the elution of olive oil and the smoking points of eluted oils. The most prominent detected volatile compounds were limonene (14.53%), piperitone (10.35%), isopropyl-5-methyl-(2E)-hexenal (8.6%), methyl octadecenoate (6.57%), and citronellyl acetate (5.87%). Both bentonite and resin were superior in decreasing the ratio of volatile compounds compared with other bleaching materials used. Resin immobilized medium was significantly affected (p < 0.05), raising the smoke point. These results highlighted some information regarding the characteristics of volatile compounds that result after the physical elution of olive oil through selected adsorbents.

Kapok fiber-supported liquid extraction for convenient oil samples preparations: A feasibility and proof-of-concept study

In this study, a novel kapok fiber-supported liquid extraction (KF-SLE) method was developed for conveniently extracting analytes from oil samples. Natural kapok fiber without any pretreatment was directly used as an oil support medium. The extraction device was conveniently constructed by directly packing some kapok fibers into a syringe tube. Due to the fibrous property of the kapok fiber, no filter plate was needed. The cost of a KF-SLE device was as low as 0.5 CNY. The KF-SLE process was conveniently conducted using a simple three-step protocol: (1) the oil sample without any pretreatment including dilution was added directedly; (2) then, the oil-immiscible extractant was added; (3) after waiting a certain time for static extraction, the extractant was eluted out by pressing the kapok fibers with the syringe plunger. The extractant could be directly transferred for subsequent instrumental detection. For the feasibility and proof-of-concept study, the method was applied to quantify four synthetic flavor chemicals in edible oils. Satisfied quantification results were obtained with the correlation coefficient (R²) being greater than 0.996, the relative recoveries ranging from 92.90% to 107.53% and intra- and inter-day RSDs being less than 7.56%. All in all, for the first time, the SLE technique was expanded to process oil samples and the method has the characteristics of low cost, environmental friendliness, high sample processing throughput and ease of automation, offering a promising approach for edible oil sample preparations.

Understanding of the residual odor of fatty esters used as emollient in cosmetic products

OBJECTIVE

Fatty esters are known for their versatility, but in addition to their performance as emollients, emulsifiers, solubilizers, or dispersing agents, they have to meet more and more criteria to be used in cosmetic products. Thus, their olfactory characteristics are expected to be as neutral as possible. However, despite a step of deodorization during the synthesis of fatty esters, a residual odor is currently still perceived at the end of the process.

METHODS

In this study, a specific analytical methodology combining sensory with chemical analyses was implemented to characterize the residual odor of two fatty esters and to determine its origin. Ethyl oleate and isononyl isononanoate were selected and underwent a sensory analysis to evaluate their odor intensity and odor profile. Volatile compounds released by these esters were assessed by GC-MS after Solid-Phase MicroExtraction (SPME) and amongst them, odor-active compounds were brought into light using Gas Chromatography coupled with Mass Spectrometry and Olfactometry (GC-MS-O) analyses.

RESULTS

On the isononyl isononanoate chromatogram, only peaks corresponding to the different isomeric ester forms were evidenced while around 70 volatile compounds were detected in the ethyl oleate headspace, including esters, aldehydes, hydrocarbons, and ketones. Isononyl alcohol used as raw material in the synthesis was proven to be responsible for isononyl isononanoate final odor. As for ethyl oleate, of the 23 odor-active compounds perceived, 14 have been identified; they are mainly esters and saturated as well as unsaturated aldehydes.

CONCLUSION

A novel measurement approach was presented to analyze trace odors of fatty esters and the results will be useful to control their deodorization by targeting appropriate strategies with the aim either to avoid the formation or remove the identified odorant compounds. This study may be further expanded by investigating the impact of deodorization on odor-active compounds for a complete understanding of their contribution to the fatty ester global odor.

Application of Chromatographic Technology to Determine Aromatic Substances in Tobacco during Natural Fermentation: A Review

Flavor is an important index to evaluate the sensory quality of tobacco. The process of fermentation is a key step in the production of aromatic substances in tobacco leaves and an important factor in improving their quality. Worldwide, reams of research show that chromatographic technology plays an irreplaceable role in the tobacco aromatic chemistry. Nevertheless, the degradation mechanism of latent aromatic compounds and the formation mechanism of characteristic aromatic substances have not been fully and systematically elucidated. In this study, the latest progress of basic methods, techniques, and research results of the separation, analysis, and identification of aromatic substances in fermented tobacco leaves were reviewed, and the next research and application directions were prospected. It is expected to provide theoretical reference for the study of molecular mechanism of tobacco flavor, reveal the degradation mechanism of potential aroma compounds, and help improve the quality of tobacco.

Identification of volatile biomarkers for high-throughput sensing of soft rot and Pythium leak diseases in stored potatoes

Soft rot and Pythium leak are postharvest storage diseases of potato tubers that can cause substantial crop losses in the US. This study focused on detecting volatile organic compounds (VOCs) associated with rot inoculated tubers during storage (up to 21 days) using headspace solid-phase microextraction (SPME) coupled to gas chromatography (GC) with mass spectrometry (MS) and flame ionization detector (FID) analysis. Russet Burbank and Ranger Russet tubers were inoculated with the rot pathogens. Static sampling with 50 min trapping time followed by GC-MS and GC-FID analysis identified 23 and 30 common VOCs from the pathogen inoculated tubers. Overall, n,n-dimethylmethylamine, acetone, 1-undecene, and styrene, occurred frequently and repeatability in inoculated samples based on GC-MS analysis, with the latter two found using GC-FID analysis as well. Identification of such biomarkers can be useful in developing high-throughput VOC sensing systems for early disease detection in potato storage facilities.

Optimisation of the HS-SPME/GC-MS Approach by Design of Experiments Combined with Chemometrics for the Classification of Cretan Virgin Olive Oils

A headspace-solid phase microextraction/gas chromatography-mass spectrometry (HS-SPME/GC-MS) method was developed herein for the analysis of virgin olive oil volatile metabolome. Optimisation of SPME conditions was performed by Design of Experiments (DoE) and Response Surface Methodology (RSM) approaches and factors, such as sample volume, sample stirring, extraction temperature and time, and desorption temperature and time, were examined to reach optimal microextraction conditions. The potential of the optimised method was then investigated for its use in the classification of Cretan virgin olive oil samples with the aid of multivariate statistical analysis. Certain markers were identified with significance in the geographical classification of Cretan extra-virgin olive oil (EVOO) samples. In total, 92 volatile organic compounds were tentatively identified and semi-quantified, and the data obtained confirm that the method is robust, reliable, and analytically powerful for olive oil classification.

Characterization of the Key Odorants Causing the Musty and Fusty/Muddy Sediment Off-Flavors in Olive Oils

Microbial spoilage of olive fruits is among the most frequent reasons for two types of off-flavors in olive oils, assigned as musty and fusty/muddy sediment. To characterize both off-flavors on a molecular level by means of the sensomics approach, the key aroma compounds in a premium extra virgin olive oil (PreOO1) eliciting the typical sensory properties were compared to those identified in two off-flavor olive oils obtained from the International Olive Council (IOC). A comparative aroma extract dilution analysis (cAEDA) followed by identification experiments revealed 53 odorants in the musty reference olive oil (MusOO1) and 48 odorants in the fusty/muddy sediment one (FusOO1). Odorants, differing in flavor dilution (FD) factors or showing a high FD factor in at least one of the olive oils, were quantitated by stable isotope dilution analysis (SIDA), followed by the calculation of odor activity values (OAVs; ratio of concentration of an odorant to the respective odor threshold in odorless refined sunflower oil). Aroma recombination and omission experiments revealed 13 key aroma compounds in MusOO1 and 12 in FusOO1. To demonstrate the importance of volatile phenols, 10 phenolic smelling odorants were quantitated in further 13 extra virgin olive oils, in 3 musty and in 13 fusty/muddy sediment defective olive oils, and in 8 olive oils with other off-flavors. Both sensory defects could successfully be discriminated from extra virgin olive oils by applying either a principal component analysis or a hierarchical cluster analysis. Considering possible reaction pathways and all results obtained including Pearson coefficients between the odorant concentrations and the intensities of the defects, specifically 2-methoxyphenol and 4-ethylphenol were proposed as marker compounds for the quality assignment of both types of off-flavors induced by microbial spoilage among the identified key aroma compounds.

Comparative Study of Volatile Compounds and Sensory Characteristics of Dalmatian Monovarietal Virgin Olive Oils

Volatile compounds are chemical species responsible for the distinctive aroma of virgin olive oil. Monovarietal olive oils have a peculiar composition of volatiles, some of which are varietal descriptors. In this paper, the total phenolic content (TPC), fatty acid composition, volatile compounds, and sensory profile of monovarietal olive oils from four Dalmatian most common olive cultivars-Oblica, Lastovka, Levantinka, and Krvavica-were studied. The volatile composition of olive oils was analyzed using headspace solid-phase microextraction with gas chromatography/mass spectrometry. The highest mean TPC value was measured in Oblica and Krvavica oils (around 438 mg/kg). The difference among cultivars for fatty acids composition was detected for C16:1, C17:0, C18:1, C18:2, and the ratio C18:1/C18:2. Krvavica oils showed clear differences in fatty acid composition compared to oils from other cultivars. The most prevalent volatile compound in all oils was C6 aldehyde E-2-hexenal, with the highest value detected in Levantinka oils (75.89%), followed by Lastovka (55.27%) and Oblica (54.86%). Oblica oils had the highest value of Z-3-hexen-1-ol, which influenced its characteristic banana fruitiness, detected only in this oil. Lastovka oils had the highest amount of several volatiles (heptanal, Z-2-heptenal, hexanal, hexyl acetate), with a unique woody sensation and the highest astringency among all studied cultivars. Levantinka oils had the highest level of almond fruitiness, while Krvavica oils had the highest level of grass fruitiness.

E-Nose and Olfactory Assessment: Teamwork or a Challenge to the Last Data? The Case of Virgin Olive Oil Stability and Shelf Life

Electronic nose (E-nose) devices represent one of the most trailblazing innovations in current technological research, since mimicking the functioning of the biological sense of smell has always represented a fascinating challenge for technological development applied to life sciences and beyond. Sensor array tools are right now used in a plethora of applications, including, but not limited to, (bio-)medical, environmental, and food industry related. In particular, the food industry has seen a significant rise in the application of technological tools for determining the quality of edibles, progressively replacing human panelists, therefore changing the whole quality control chain in the field. To this end, the present review, conducted on PubMed, Science Direct and Web of Science, screening papers published between January 2010 and May 2021, sought to investigate the current trends in the usage of human panels and sensorized tools (E-nose and similar) in the food industry, comparing the performances between the two different approaches. In particular, the focus was mainly addressed towards the stability and shelf life assessment of olive oil, the main constituent of the renowned “Mediterranean diet”, and nowadays appreciated in cuisines from all around the world. The obtained results demonstrate that, despite the satisfying performances of both approaches, the best strategy merges the potentialities of human sensory panels and technological sensor arrays, (i.e., E-nose somewhat supported by E-tongue and/or E-eye). The current investigation can be used as a reference for future guidance towards the choice between human panelists and sensorized tools, to the benefit of food manufacturers.

Unraveling of the Aroma-Active Compounds in Virgin Camellia Oil (Camellia oleifera Abel) Using Gas Chromatography-Mass Spectrometry-Olfactometry, Aroma Recombination, and Omission Studies

Camellia oil is a popular edible oil in China as a result of its nutritional properties. However, the key odorants of camellia oil remain unclear. In this study, the volatiles of virgin camellia oil (VCO) were extracted by solvent-assisted and non-solvent-assisted methods. A total of 66 volatile compounds were identified using gas chromatography-mass spectrometry-olfactometry, with flavor dilution factors ranging from 1 to 729 via aroma extraction dilution analysis. Among them, 10 odorants were identified for the first time in VCO. Moreover, 41 volatiles were confirmed as aroma-active compounds with odor activity values greater than 1. Aroma recombination and omission studies demonstrated that aldehydes, esters, acids, and heterocyclic compounds significantly contribute to the aroma profiles of VCO. Hexanal, octanal, (E,E)-2,4-heptadienal, (E,E)-2,4-nonadienal, decyl acetate, ethyl benzoate, ethyl 2-methylbutanoate, 2-methylbutyl (Z)-2-methyl-2-butenoate, 2-methylbutanoic acid, hexanoic acid, 2-pentylfuran, and 2-methyl-3-furanthiol could impart roasted-like, nut-like, fat-like, fruit-like, grass-like, and sweat-like odors and were the key odorants in VCO. The lipoxygenase pathway was possibly responsible for the formation of key odorants in VCO. This work provides an extract aroma consistent for virgin camellia oil.

Instrumental Techniques to Classify Olive Oils according to Their Quality

This review includes an update of the publications on quality classification of olive oils into extra, virgin or lampante olive oil categories. Nowadays, the official method to carry out this classification is time-consuming and, sometimes, it is not systematic and/or objective. It is based on conventional physicochemical analysis and on a sensorial tasting of olive oils carried out by a panel of experts. The aim of this review was to explore and give value to the alternative techniques reported in the bibliography to complement the current official methods established for that classification of olive oils. Specifically considered were non-separation and separation analytical techniques which could contribute to correctly classify olive oils according to their physicochemical and/or sensorial characteristics. An in-depth description has been written on the methods used to differentiate these three types of olive oils and the main advantages and disadvantages of the proposed procedures. The techniques here reviewed could be a real and fast option to complement or even substitute some of the analysis included in the official method. Finally, general trends and detected difficulties found to address this issue have been discussed throughout the article.

Volatile Profile of Two-Phase Olive Pomace (Alperujo) by HS-SPME-GC-MS as a Key to Defining Volatile Markers of Sensory Defects Caused by Biological Phenomena in Virgin Olive Oil

An olive pomace from the two-phase decanter stored in different conditions was used as a model to simulate the detrimental biological phenomena occurring during olive oil processing and storage. A group of EVOO and defective oils were also analyzed. The volatile fraction was studied with HS-SPME-GC-MS; 127 volatiles were identified (55 of which tentatively identified) and evaluated over time. Seven volatiles were tentatively identified for the first time in olive oil; the role of C6 alcohols in detrimental biological phenomena was highlighted. Suitable volatile markers for defects of microbiological origin were defined, particularly the fusty/muddy sediment. They were then applied to olive oils with different quality categories; one of the markers was able to discriminate among EVOOs and all the defective samples, including the borderline ones. The marker was constituted by the sum of concentrations of 10 esters, 4 alcohols, 1 ketone, and 1 α-hydroxy-ketone but no carboxylic acids.

Development and optimization of a quantitative analysis of main odorants causing off flavours in cork stoppers using headspace solid-phase microextraction gas chromatography tandem mass spectrometry

A simple and sensitive method was developed and validated to simultaneously separate and determine the 2-Methoxy-3,5-dimethylpyrazine, 2-Isopropyl-3-methoxypyrazine, guaiacol, 2-Isobutyl-3-methoxypyrazine, 2-Methylisoborneol, geosmin, 2,4,6-Trichloroanisole, 2,3,4,6-Tetrachloroanisole, 2,4,6-Tribromoanisole and Pentachloroanisole in cork stoppers via headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography tandem mass spectrometry (GC-MS/MS). The influence of the fibre coating used, the extraction times and temperatures, the sodium chloride additions and the desorption temperatures were investigated. Once done, the optimial HS-SPME conditions established were divinylbenzene/carboxenpolydimethylsiloxane/polydimethylsiloxane (DVB/CAR/PDMS) fibres, a 50°C extraction temperature, 60-min extraction time, an ionic strength of 3-g sodium chlorid and a 290°C desorption temperature. The method showed a good linearity (R2  ≥ 0.994) within the tested range (from 0.1 to 50 ng L-1 ) for all the compounds. Using TCA-d10 and MIB-d3 as internal standards the precision, expressed as repeatability and reproducibility RSD, was <10% in both. Note that the limits of quantifications (LOQs) are below the sensory threshold levels for such compounds in water and wine. Good recoveries were obtained for cork macerates (from 100.4% to 126%) and when compared with other reported methods using HS-SPME in water and cork stopper samples, the present method had more analytes with the lowest limit of detection for most of the targeted compounds, along with good precision and recovery.

Prediction of Fruity Aroma Intensity and Defect Presence in Virgin Olive Oil Using an Electronic Nose

The organoleptic profile of a Virgin Olive Oil is a key quality parameter that is currently obtained by human sensory panels. The development of an instrumental technique capable of providing information about this profile quickly and online is of great interest. This work employed a general purpose e-nose, in lab conditions, to predict the level of fruity aroma and the presence of defects in Virgin Olive Oils. The raw data provided by the e-nose were used to extract a set of features that fed a regressor to predict the level of fruity aroma and a classifier to detect the presence of defects. The results obtained were a mean validation error of 0.5 units for the prediction of fruity aroma using lasso regression; and 88% accuracy for the defect detection using logistic regression. Finally, the identification of two out of ten specific sensors of the e-nose that can provide successful results paves the way to the design of low-cost specific electronic noses for this application.

Virgin Olive Oil Volatile Compounds: Composition, Sensory Characteristics, Analytical Approaches, Quality Control, and Authentication

Volatile organic compounds strongly contribute to both the positive and negative sensory attributes of virgin olive oil, and more and more studies have been published in recent years focusing on several aspects regarding these molecules. This Review is aimed at giving an overview on the state of the art about the virgin olive oil volatile compounds. Particular emphasis was given to the composition of the volatile fraction, the analytical issues and approaches for analysis, the sensory characteristics and interaction with phenolic compounds, and the approaches for supporting the Panel Test in virgin olive oil classification and in authentication of the botanical and geographic origin based on volatile compounds. A pair of detailed tables with a total of approximately 700 volatiles identified or tentatively identified to date and tables dealing with analytical procedures, sensory characteristics of volatiles, and specific chemometric approaches for quality assessment are also provided.

Formulations of Rancid and Winey-Vinegary Artificial Olfactory Reference Materials (AORMs) for Virgin Olive Oil Sensory Evaluation

Sensory assessment of virgin olive oil (“panel test”) is the only sensory method included in international regulations of edible oils and its application is compulsory. Even if its application has been a success in quality control, improving the quality of virgin olive oils over the last 30 years, at present, there is no reference material (RM), in the strict sense of the term, to be used as a validated standard for sensory defects of virgin olive oil with which tasters can be trained. Usually, real samples of virgin olive oils assessed by many panels for the International Olive Council (IOC) ring tests are used as materials of reference in panel training and control. The latter are highly representative of the main perceived defects, but availability is limited, samples are not homogeneous year after year, and other secondary defects can be present. Thus, in order to provide solutions, this work describes an analytical procedure for implementing olfactory formulations that emulate rancid and winey-vinegary defects found in virgin olive oils with the aim of providing reproducible RMs that can be prepared on demand. A strategy for designing RMs for aroma is presented and the optimization process to obtain the best formulation is described. Under the criteria of representativeness, verified with the advice of the IOC, aroma persistence, and simplicity in formulation, two RMs for winey-vinegary and rancid were obtained by diluting acetic acid and ethanol (winey-vinegary defect) and hexanal (rancid defect) together with other compounds that are used to modify aroma and avoid non-natural sensory notes.

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

The commercial category of virgin olive oil is currently assigned on the basis of chemical-physical and sensory parameters following official methods. Considering the limited number of samples that can be analysed daily by a sensory panel, an instrumental screening tool could be supportive by reducing the assessors’ workload and improving their performance. The present work aims to in-house validate a screening strategy consisting of two sequential binary partial least squares-discriminant analysis (PLS-DA) models that was suggested to be successful in a proof-of-concept study. This approach is based on the volatile fraction fingerprint obtained by HS-SPME–GC–MS from more than 300 virgin olive oils from two crop seasons graded by six different sensory panels into extra virgin, virgin or lampante categories. Uncertainty ranges were set for the binary classification models according to sensitivity and specificity by means of receiver operating characteristics (ROC) curves, aiming to identify boundary samples. Thereby, performing the screening approach, only the virgin olive oils classified as uncertain (23.3%) would be assessed by a sensory panel, while the rest would be directly classified into a given commercial category (78.9% of correct classification). The sensory panel’s workload would be reduced to less than one-third of the samples. A highly reliable classification of samples would be achieved (84.0%) by combining the proposed screening tool with the reference method (panel test) for the assessment of uncertain samples.

Headspace Gas Chromatography Coupled to Mass Spectrometry and Ion Mobility Spectrometry: Classification of Virgin Olive Oils as a Study Case

Due to its multiple advantages, ion mobility spectrometry (IMS) is being considered as a complementary technique to mass spectrometry (MS). The goal of this work is to investigate and compare the capacity of IMS and MS in the classification of olive oil according to its quality. For this purpose, two analytical methods based on headspace gas chromatography (HS-GC) coupled with MS or with IMS have been optimized and characterized for the determination of volatile organic compounds from olive oil samples. Both detectors were compared in terms of sensitivity and selectivity, demonstrating that complementary data were obtained and both detectors have proven to be complementary. MS and IMS showed similar selectivity (10 out of 38 compounds were detected by HS-GC-IMS, whereas twelve compounds were detected by HS-GC-MS). However, IMS presented slightly better sensitivity (Limits of quantification (LOQ) ranged between 0.08 and 0.8 µg g⁻¹ for HS-GC-IMS, and between 0.2 and 2.1 µg g⁻¹ for HS-GC-MS). Finally, the potential of both detectors coupled with HS-GC for classification of olive oil samples depending on its quality was investigated. In this case, similar results were obtained when using both HS-GC-MS and HS-GC-IMS equipment (85.71 % of samples of the external validation set were classified correctly (validation rate)) and, although both techniques were shown to be complementary, data fusion did not improve validation results (80.95% validation rate).

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

This research aims to develop a classification model based on untargeted elaboration of volatile fraction fingerprints of virgin olive oils (n = 331) analyzed by flash gas chromatography to predict the commercial category of samples (extra virgin olive oil, EVOO; virgin olive oil, VOO; lampante olive oil, LOO). The raw data related to volatile profiles were considered as independent variables, while the quality grades provided by sensory assessment were defined as a reference parameter. This data matrix was elaborated using the linear technique partial least squares-discriminant analysis (PLS-DA), applying, in sequence, two sequential classification models with two categories (EVOO vs. no-EVOO followed by VOO vs. LOO and LOO vs. no-LOO followed by VOO vs. EVOO). The results from this large set of samples provide satisfactory percentages of correctly classified samples, ranging from 72% to 85%, in external validation. This confirms the reliability of this approach in rapid screening of quality grades and that it represents a valid solution for supporting sensory panels, increasing the efficiency of the controls, and also applicable to the industrial sector.

From Extra Virgin Olive Oil to Refined Products: Intensity and Balance Shifts of the Volatile Compounds versus Odor

To explore relationships between the volatile organic compounds (VOCs) of different grades of olive oils (OOs) (extra virgin olive oil (EVOO), refined olive oil (ROO), and pomace olive oil (POO)) and odor quality, VOCs were measured in the headspace of the oils by proton transfer reaction quadrupole ion guide time-of-flight mass spectrometry. The concentrations of most VOCs differed significantly between the grades (EVOO > ROO > POO), whereas the abundance of m/z 47.012 (formic acid), m/z 49.016 (fragments), m/z 49.027 (fragments), and m/z 115.111 (heptanal/heptanone) increased in that order. Although the refined oils had considerably lower VOC abundance, the extent of the decline varied with the VOCs. This results in differences in VOCs proportions. The high VOC abundance in the EVOO headspace in comparison to ROO and POO results in a richer and more complex odor. The identified C5–C6 compounds are expected to contribute mainly to the green odor notes, while the identified C1–C4 and C7–C15 are mainly responsible for odor defects of OOs. Current results reveal that processing strongly affects both the quantitative and relative abundance of the VOCs and, therefore, the odor quality of the various grades of OOs.

Virgin olive oil metabolomics: A review

Metabolomics involvement in the study of foods is steadily growing. Such a rise is a consequence of the increasing demand in the food sector to address challenges regarding the issues of food safety, quality, and authenticity in a more comprehensive way. Virgin olive oil (VOO) is a key product of the Mediterranean diet, with a globalized consumer interest as it may be associated with various nutritional and health benefits. Despite the strict legislation to protect this high added-value agricultural commodity and offer guarantees to consumers and honest producers, there are still analytical issues needing to be further addressed. Thus, this review aims to present the efforts made using targeted and untargeted metabolomics approaches, namely nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry-based techniques (mainly LC/GC-MS) combined with multivariate statistical analysis. Case-studies focusing on geographical/varietal classification and detection of adulteration are discussed with regards to the identification of possible markers. The advantages and limitations of each of the aforementioned techniques applied to VOO analysis are also highlighted.

Enhancement of volatile profiling using multiple-cumulative trapping solid-phase microextraction. Consideration on sample volume

In the present work, the performance of the multiple-cumulative trapping headspace solid-phase microextraction technique used in the headspace linearity range and saturated headspace was investigated and compared, with the ultimate goal of maximizing the fingerprinting information extractable using a cross-sample comparison algorithm for olive oil quality assessment. It was highlighted as the use of 0.1 g of olive oil provides comparable or even better profiling than 1.5 g at a little expense of sensitivity. However, the use of multiple-cumulative-solid-phase microextraction, along with the correct sample volume, improved not only the overall sensitivity but significantly burst the level of information for cross-sample studies.

Biophenolic Compounds Influence the In-Mouth Perceived Intensity of Virgin Olive Oil Flavours and Off-Flavours

In this study, the influence of phenolic compounds on the sensory scores attributed to extra virgin olive oil (EVOO) by panel test was investigated. Two model olive oils (MOOs) with identical concentrations of volatile compounds, differing only in the amount of biophenols (297 vs. 511 mg kg⁻¹), were analysed by two official panels and by SPME-GC/MS. Six other MOOs set up by the two previous models were also tested and analysed. They were formulated separately with the addition of three off-flavours (‘rancid’, ‘winey–vinegary’ and ‘fusty–muddy’). While high levels of EVOO phenolic compounds did not produce any effect on the headspace concentration of volatile compounds, they did affect the scores of both positive and negative sensory attributes of EVOO, due to the well-known in-mouth interactions between EVOO phenols, saliva and volatile compounds. In particular, a decrease of about 39% in the positive fruity score was found in the presence of a higher concentration of phenols. Regarding EVOO off-flavours, the higher level of phenolic compounds decreased by about 23% the score of ‘fusty–muddy’ defect and increased the score of ‘winey–vinegary’ defect about 733%. No important effect of EVOO phenolics on the perceived intensity of the ‘rancid’ defect was found. These findings could be helpful in explaining some discrepancies of panel test responses observed during extra virgin olive oil shelf life.

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

Virgin olive oil is inevitably subject to an oxidation process during storage that can affect its stability and quality due to off-flavors that develop before the oil surpasses its ‘best before’ date. Many parameters are involved in the oxidation process at moderate conditions. Therefore, a multiparametric study is necessary to establish a link between physico-chemical changes and sensory quality degradation in a real storage experiment. In this context, a storage experiment of 27 months was performed for four monovarietal virgin olive oils, bottled in transparent 500-mL PET bottles and subjected to conditions close to a supermarket scenario. Volatile composition, quality parameters and phenolic compounds were determined monthly. Simultaneously, an accredited sensory panel assessed their sensory characteristics. The stability of the fresh samples was also studied with the oxidative stability index (OSI) and mesh cell-FTIR. (E)-2-hexenal, (Z)-3-hexen-1-ol and (E)-2-hexen-1-ol were identified as markers of the fruity attribute. Hexanal and nonanal were also identified as compounds that were associated with the rise of median of defect during storage. Some disagreements were observed between the sensory assessment and the OSI analyzed by Rancimat. However, the increase of concentration of rancid markers agreed with the increase of aldehyde band measured with mesh cell-FTIR.

Alignment and Proficiency of Virgin Olive Oil Sensory Panels: The OLEUM Approach

A set of 334 commercial virgin olive oil (VOO) samples were evaluated by six sensory panels during the H2020 OLEUM project. Sensory data were elaborated with two main objectives: (i) to classify and characterize samples in order to use them for possible correlations with physical–chemical data and (ii) to monitor and improve the performance of panels. After revision of the IOC guidelines in 2018, this work represents the first published attempt to verify some of the recommended quality control tools to increase harmonization among panels. Specifically, a new “decision tree” scheme was developed, and some IOC quality control procedures were applied. The adoption of these tools allowed for reliable classification of 289 of 334 VOOs; for the remaining 45, misalignments between panels of first (on the category, 21 cases) or second type (on the main perceived defect, 24 cases) occurred. In these cases, a “formative reassessment” was necessary. At the end, 329 of 334 VOOs (98.5%) were classified, thus confirming the effectiveness of this approach to achieve a better proficiency. The panels showed good performance, but the need to adopt new reference materials that are stable and reproducible to improve the panel’s skills and agreement also emerged.

Comprehensive analysis of volatile compounds in cold-pressed safflower seed oil from Xinjiang, China

Three varieties of safflower seed oil (SSO) from Xinjiang Autonomous Region, China, were analyzed by headspace solid-phase micro-extraction gas chromatography coupled with mass spectrometry (HS-SPME-GC-MS) to reveal volatile components. Overall, 67 volatile components were determined and four compounds including isoamyl alcohol, caproic acid, n-pentanal, and heptanal were newly identified in SSO as aroma-active components. Meanwhile, 16 compounds were selected by relative odor activity value (ROAV) to evaluate contributions of single compounds to the overall odor (ROAV > 1), in which nonanal, (Z)-6-nonenal, and (E)-2,4-decadienal were the top three contributed substances (ROAV > 70). The sensory panel was described as eight definition terms (grassy, fruity, almond, mushroom, fatty, sweet, paddy, and overall fragrance). Principal component analysis (PCA) revealed a significant separation of three cultivars with the first principal component (PC-1) and the second principal component (PC-2) expressing 73.9% and 23.1%, respectively. Both PCA and ROAV allowed identifying the compounds positively correlated to sensory evaluation.

Exposure of Human Gastric Cells to Oxidized Lipids Stimulates Pathways of Amino Acid Biosynthesis on a Genomic and Metabolomic Level

The Western diet is characterized by a high consumption of heat-treated fats and oils. During deep-frying processes, vegetable oils are subjected to high temperatures which result in the formation of lipid peroxidation products. Dietary intake of oxidized vegetable oils has been associated with various biological effects, whereas knowledge about the effects of structurally-characterized lipid peroxidation products and their possible absorption into the body is scarce. This study investigates the impact of linoleic acid, one of the most abundant polyunsaturated fatty acids in vegetable oils, and its primary and secondary peroxidation products, 13-HpODE and hexanal, on genomic and metabolomic pathways in human gastric cells (HGT-1) in culture. The genomic and metabolomic approach was preceded by an up-to-six-hour exposure study applying 100 µM of each test compound to the apical compartment in order to quantitate the compounds’ recovery at the basolateral side. Exposure of HGT-1 cells to either 100 µM linoleic acid or 100 µM 13-HpODE resulted in the formation of approximately 1 µM of the corresponding hydroxy fatty acid, 13-HODE, in the basolateral compartment, whereas a mean concentration of 0.20 ± 0.13 µM hexanal was quantitated after an equivalent application of 100 µM hexanal. An integrated genomic and metabolomic pathway analysis revealed an impact of the linoleic acid peroxidation products, 13-HpODE and hexanal, primarily on pathways related to amino acid biosynthesis (p < 0.05), indicating that peroxidation of linoleic acid plays an important role in the regulation of intracellular amino acid biosynthesis.

Biochemical composition and antioxidant activity of three extra virgin olive oils from the Irpinia Province, Southern Italy

Extra virgin olive oil (EVOO), appraised for its healthy properties, represents an important element for the economy of several countries of the Mediterranean area, including Italy. Our study aimed to evaluate some biochemical characteristics (polyphenols and volatile compounds) as well as the antioxidant activity of three EVOOs obtained from the varieties Ravece, Ogliarola, and Ruvea antica, grown in the same field of an Irpinian village, Montella, in the Campania region, Southern Italy. Extra virgin olive oil Ruvea antica contained the greatest amount of total polyphenols and showed the highest antioxidant activity. Principal component analysis of the aromatic profiles indicated that the three EVOOs could be easily discriminated according to the cultivar. 1-Hexanol, 2-hexen-1-ol, 3-pentanone, representing the most abundant volatiles of the EVOO Ruvea antica, and 2-hexenal, which resulted the main component in EVOOs Ogliarola and Ravece, could be considered as markers to discriminate these three EVOOs, according to the ReliefF feature selection algorithm.

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

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.

The Role of Knowledge in Constructing the Quality of Olive Oil in Spain

The sustainability of a large proportion of Spanish olive oil-producing territories depends to a great extent on their capacity to fit into a specific model of food quality. The strategies used in the different territories differ with respect to their adherence to the objectifiable conception of quality, based on scientific-technical knowledge, or subjectivating conception of quality, based on tacit and practical knowledge. In this paper, we analyse the route taken by two territories with olive oil protected designation of origin (PDO) status in Spain to construct their quality model, the type of knowledge that has been applied and how knowledge processes affect the construction of sustainable quality models. This study applies a qualitative methodology based on participative observation and semi-structured interviews with key actors of the territories. The results indicate that processes of production, reproduction and dissemination of knowledge are basic pillars for the construction of sustainable quality projects. The degree of understanding of the objectifiable and subjectivating conception of quality in olive-producing territories and the interaction between them depend on the specific characteristics of the territory, the objectives set in connection to the olive oil quality method, the importance given to the different types of knowledge, and its standing on the issue of territorial sustainability.

Highly Informative Fingerprinting of Extra-Virgin Olive Oil Volatiles: The Role of High Concentration-Capacity Sampling in Combination with Comprehensive Two-Dimensional Gas Chromatography

The study explores the complex volatile fraction of extra-virgin olive oil by combining high concentration-capacity headspace approaches with comprehensive two-dimensional gas chromatography, which is coupled with time of flight mass spectrometry. The static headspace techniques in this study are: (a) Solid-phase microextraction, with multi-polymer coating (SPME- Divinylbenzene/Carboxen/Polydimethylsiloxane), which is taken as the reference technique; (b) headspace sorptive extraction (HSSE) with either a single-material coating (polydimethylsiloxane—PDMS) or a dual-phase coating that combines PDMS/Carbopack and PDMS/EG (ethyleneglycol); (c) monolithic material sorptive extraction (MMSE), using octa-decyl silica combined with graphite carbon (ODS/CB); and dynamic headspace (d) with either PDMS foam, operating in partition mode, or Tenax TA™, operating in adsorption mode. The coverage of both targeted and untargeted 2D-peak-region features, which corresponds to detectable analytes, was examined, while concentration factors (CF) for a selection of informative analytes, including key-odorants and off-odors, and homolog-series relative ratios were calculated and the information capacity was discussed. The results highlighted the differences in concentration capacities, which were mainly caused by polymer-accumulation characteristics (sorptive/adsorptive materials) and its amount. The relative concentration capacity for homologues and potent odorants was also discussed, while headspace linearity and the relative distribution of analytes, as a function of different sampling amounts, was examined. This last point is of particular interest in quantitative studies where accurate data is needed to derive consistent conclusions.

Comparative Analysis of Volatiles of 15 Brands of Extra-Virgin Olive Oils Using Solid-Phase Micro-Extraction and Solvent-Assisted Flavor Evaporation

Aroma profiles, key aroma compound quantification, and cluster analysis of 15 brands of extra-virgin olive oils (EVOOs) from three countries (Spain, Italy, and Greece) were investigated in the current study. Aroma compounds were isolated from the oil by using solvent-assisted flavor evaporation (SAFE) and solid-phase micro-extraction (SPME) and analyzed by gas chromatography-olfactometry mass spectrometry (GC-MS/O). A total of 89 compounds were screened by SPME/SAFE-GC-MS/O with chromatographic columns in 15 brands of samples. Eighty and 54 compounds were respectively identified by SPME- and SAFE-GC-MS/O. Of those, 44 compounds were detected by both methods. Undecanol, (Z)-4-decenal, (E)-2-dodecenal, and 2-nonanone extracted by SAFE were not found in EVOOs before. Eight classes of aroma compounds were identified, including 17 alcohols, 22 aldehydes, 9 ketones, 4 acids, 14 esters, 5 aromatics, 12 alkene, and 6 others. Eleven compounds were identified as the key aroma compounds in alternative brands of EVOOs by SAFE-aroma extract dilution analysis (AEDA). Hexanal, (E)-2-hexenal, (E)-3-hexenol, acetic acid, and (E)-2-heptenal were the common key aroma compounds by AEDA and odor activity values (OAVs). From the cluster analysis of the heatmap, the aroma compounds of all the Spain EVOOs were similar, and there were some differences from the samples of Italy and Greece. It suggested that both the amount and concentration of aroma compounds determine the similarity of aroma in EVOOs.

Analysis of Oxidative Carbonyl Compounds by UPLC-High-Resolution Mass Spectrometry in Milk Powder

Long-chain polyunsaturated fatty acids are highly susceptible to lipid oxidation which causes undesirable odors and flavors in food. We present the development, validation, and application of a semiquantitative screening method to monitor volatile and nonvolatile carbonyl compounds generated from lipids oxidation after 7-(diethylamino)-2-oxochromene-3-carbohydrazide (CHH) derivatization using liquid chromatography high-resolution mass spectrometry. An inclusion list containing eligible compounds was used in full scan mode to identify potential oxidative markers. In an antioxidants study using lecithin and tocopherols, the proposed method was successfully used to monitor the docosahexaenoic acid (DHA)-specific oxidative markers in a model milk powder system enriched with fish oils. The results showed that lecithin inhibits oxidation by reducing the peroxidation rate, while δ-tocopherol delays the oxidation with distinct induction periods. Here, we explore the optimum concentration of soy lecithin and δ-tocopherol needed to limit lipid oxidation in a complex food matrix such as milk powder.

Implementing Dynamic Headspace With SPME Sampling of Virgin Olive Oil Volatiles: Optimization, Quality Analytical Study, and Performance Testing

Competition and interaction phenomena among volatiles during their adsorption process by solid phase microextraction (SPME) fibers in static headspace sampling procedure (SHS) cast doubt on its ability to quantify virgin olive oil volatiles. SPME fibers being excellent traps, their use was analyzed with a new device allowing the concentration of volatiles in a dynamic headspace sampling procedure (DHS). A central composite experimental design optimized the main variables of the device (4 g sample weight, 40 °C temperature, 150 mL/min flow rate, 50 min adsorption time), while values of the analytical quality control parameters of the method (repeatability, limits of detection and quantification, working range, sensitivity, and resolution) were compared with those ones from static headspace. DHS shows better precision results for aldehydes and alcohols than SHS and allowed analyzing higher concentrations with no problem of saturation. In 19 of 28 compounds analyzed in 50 samples the chromatographic areas were higher when running DHS. The concentration values of volatile compounds in these samples after applying SHS and DHS are discussed together with the ability of the new method for distinguishing virgin olive oil by their categories (extra virgin, virgin, and lampante) by the volatiles quantified in commercial oils.