First comprehensive characterization of volatile profile of north Moroccan olive oils: A geographic discriminant approach

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.

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.

Volatile-Olfactory Profiles of cv. Arbequina Olive Oils Extracted without/with Olive Leaves Addition and Their Discrimination Using an Electronic Nose

Oils from cv. Arbequina were industrially extracted together with olive leaves of cv. Arbequina or Santulhana (1%, w/w), and their olfactory and volatile profiles were compared to those extracted without leaves addition (control). The leaves incorporation resulted in green fruity oils with fresh herbs and cabbage olfactory notes, while control oils showed a ripe fruity sensation with banana, apple, and dry hay grass notes. In all oils, total volatile contents varied from 57.5 to 65.5 mg/kg (internal standard equivalents), being aldehydes followed by esters, hydrocarbons, and alcohols the most abundant classes. No differences in the number of volatiles were observed. The incorporation of cv. Arbequina or Santulhana leaves significantly reduced the total content of alcohols and esters (minus 37–56% and 10–13%, respectively). Contrary, cv. Arbequina leaves did not influence the total content of aldehydes or hydrocarbons, while cv. Santulhana leaves promoted a significant increase (plus 49 and 10%, respectively). Thus, a leaf-cultivar dependency was observed, tentatively attributed to enzymatic differences related to the lipoxygenase pathway. Olfactory or volatile profiles allowed the successful unsupervised differentiation of the three types of studied cv. Arbequina oils. Finally, a lab-made electronic nose was applied to allow the nondestructive discrimination of cv. Arbequina oils extracted with or without the incorporation of olive leaves (100% and 99 ± 5% of correct classifications for leave-one-out and repeated K-fold cross-validation variants), being a practical tool for ensuring the label correctness if future commercialization is envisaged. Moreover, this finding also strengthened that olive oils extracted with or without olive leaves incorporation possessed quite different olfactory patterns, which also depended on the cultivar of the olive leaves.

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.

Geographical origin discrimination of "Ntopia" olive oil cultivar from Ionian islands using volatile compounds analysis and computational statistics

The aim of the present study was to characterize the aroma profile of olive oil of the "Ntopia" (local) cultivar from the Ionian islands (Zakynthos, Kefalonia, Leukada, and Kerkyra) (Greece), and investigate whether specific volatile compounds could be considered as indicators of olive oil geographical origin, using computational statistics. In this context, 137 olive oil samples were subjected to headspace solid phase microextraction coupled to gas chromatography/mass spectrometry using the internal standard method. Computational statistics on the semi-quantitative data of olive oil samples, as rapid machine learning algorithms, showed that specific volatile compounds could be used as indicators of geographical origin of olive oil of the "Ntopia" cultivar, among the four main Ionian islands. Volatile compounds such as ethanol, pentanal, 2,4-dimethylheptane, 3,7-dimethyl-1,3,6-octatriene (E), 2,5-dimethylnonane, 1-hexanol, 6-methyl-5-hepten-2-one, octanal, dl-Limonene, acetic acid hexyl ester and dodecane could aid to the geographical origin discrimination of "Ntopia" olive oil cultivar when two (Zakynthos and Kefalonia) or four (Zakynthos, Kefalonia, Leukada and Kerkyra) Ionian islands are subjected to statistical analysis. The discrimination rate using the cross-validation method was 100% and 85.7%, respectively. These results were further evaluated using training and holdout partitions, during which a comparable classification rate was obtained.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s00217-021-03863-2.

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.

Characterization of olive oil flavored with Brazilian pink pepper (Schinus terebinthifolius Raddi) in different maceration processes

The present study aimed to evaluate two different processes of olive oil aromatization with Schinus terebinthifolius Raddi, conventional maceration (CM) and ultrasound-assisted maceration (UM), and their influence on quality parameters, total phenolic compounds (TPC), fatty acid profile (FA), volatile organic compounds (VOCs), antioxidant capacity, and oxidative stability. Flavoring reduced peroxide values, although it increased free fatty acids and extinction coefficients. The flavorization process did not change the FA profile, which showed oleic acid as a major compound. The VOCs varied and the migration of oxygenated monoterpenes were more effective in UM-flavored olive oil compared to its CM counterpart. All flavored olive oils presented higher oxidative stability than the control samples and UM-flavored olive oil was highlighted for its higher antioxidant activity. These findings proved that aromatization with pink pepper assisted by ultrasound may be an alternative to improve olive oil quality and create a new competitive flavored product.

Determination of volatile compounds responsible for sensory characteristics from Brazilian extra virgin olive oil using HS-SPME/GC-MS direct method

Producing of extra virgin olive oils (EVOOs) containing pleasant sensory notes depends on fruits quality and production process and is strongly associated with their classification that is based on aroma and sensory taste. Consolidated as an efficient method, the direct headspace solid phase microextraction technique (HS-SPME) was utilized to characterize the volatile organic compounds (VOCs) profile, which contributes to the aroma of olive oils from southwestern (Serra da Mantiqueira region) and southern (Campanha Gaúcha region) Brazil. In this work, the relationship between the VOCs and sensory characteristics has been established; 19 EVOO samples (12 from Campanha Gaúcha and 7 from Serra da Mantiqueira) were studied. Indeed, the main volatile compounds were analyzed and grouped by their classification as well stood up with the trained sensorial panel perceptions. Relevant correlation between artichoke notes and ripe EVOO and between herbaceous notes and green EVOO was found. Additional correlations were observed for C5 and C6 VOCs with green and fruit/floral notes. The results denote the high quality among the samples and imply that besides the genetic factor, ripe or green classification influenced the volatile composition. PRACTICAL APPLICATION: As the Brazilian olive oil production is increasing, knowing about different sensory characteristics and its correlation with the volatile compounds of extra virgin olive oil represents a good tool to improve the quality. Moreover, the application of direct SPME method was possible evidence in the differentiation of ripe and green olive oils, beyond the production region and in consonance with its sensory notes and characteristics.

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).

Volatile and Sensory Profiles of Algerian Extra-Virgin Olive Oil from Souidi and Zeletni Cultivars

In this study, the volatile and sensory profiles of monovarietal extra-virgin olive oil (EVOO) from two less widespread Algerian autochthonous cultivars (Souidi and Zeletni) were obtained using headspace solid-phase microextraction coupled to gas chromatography-mass spectrometry and a panel test, respectively. A total of 14 and 10 volatile compounds belonging to different chemical classes were identified and quantified in the Souidi and Zeletni EVOOs, respectively. Zeletni EVOO contains 2.07 times more (E)-2-hexenal than Souidi EVOO. In addition, the amounts of C6 compounds from LA and LnA, as well as the total amount of the compounds of the LOX pathway were higher in Zeletni than in the Souidi EVOO. Another important finding was the predominance of sesquiterpene β-ocimene in the composition of the volatile fraction of Souidi EVOO. The sensory profiles of the EVOOs analyzed were characterized by fruity, bitter and pungent sensory positive attributes, perceived at medium intensity in both oils studied.

"Biosynthesis of volatile compounds by hydroperoxide lyase enzymatic activity during virgin olive oil extraction process"

The approach of this research was to describe the biochemical transformations of minor components of virgin olive oil with high impact on its sensory quality, specifically "volatile compounds" during its extraction process. For this purpose `Picual´, `Arbequina´ and `Hojiblanca´ cultivars were processed at three different harvesting times. Their volatile profiles and levels of enzymatic activity of "hydroperoxide lyase", responsible for the biosynthesis of C6 aldehydes related to "green and fruity notes", were monitored and identified in mesocarp, paste before kneading and paste after kneading based on the catalytic action of crude enzyme extracts. Both of them, volatiles and HPL, were analyzed by incubating with their corresponding substrates and reaction products formed were analyzed by Solid Phase Microextraction-Gas Chromatography and Mass Spectrometry. The results obtained in the present research can be useful in order to develop new markers biochemical whereby improved aroma quality in olive breeding programs or in the design of new protocol of VOO extraction.

Changes in Virgin Olive Oil Volatiles Caused by in Vitro Digestion

Volatile compounds are responsible for some sensory characteristics of virgin olive oil (VOO); however, they have not been studied from a nutritional point view. In this work, the effect of the simulated digestion on VOO volatile compounds responsible for green flavor was studied, analyzing their changes through the three steps of an in vitro digestion model (mouth, stomach, and small intestine). Index of recovery and bioaccessibility were determined for the main volatiles of "Picual" VOO. At end of the duodenal step, higher recoveries of ethanol, pent-1-en-3-ol, β-ocimene, and nonanal were observed. From the 10 volatile compounds analyzed, only six compounds were bioaccessible. The compounds with the highest bioaccessibility were pent-1-en-3-ol, nonanal, β-ocimene, and ethanol. The results showed for the first time the recovery and bioaccessibility of several volatile compounds present in VOO.

Global volatile profile of virgin olive oils flavoured by aromatic/medicinal plants

The global volatile profile of commercial virgin olive oils and flavoured olive oils with aromatic/medicinal plants, was established using liquid-liquid microextraction (LLME) and headspace solid-phase microextraction (HS-SPME) combined with gas chromatography-quadrupole mass spectrometry (GC-qMS). More than 60 volatile organic compounds (VOCs belonging to different groups were identified using both methods. Olive oils volatile profile was slightly influenced by maceration process, which occurred at room temperature (20±2°C) for 15days. The predominant differences were observed in terpenoids group, since some of them were only identified in the flavoured olive oils, while others showed an increase with the maceration process. VOCs mass transfer from plants to olive oils could explain the observed results. Principal components analysis (PCA) applied to LLME/GC-qMS data allowed to distinguish the olive oils. The flavoured oils would increase the use of olive oil among consumers as consequence of the improvement of its aromatic profile and healthy properties.