Sensory and Volatile Profiles of Monovarietal North Tunisian Extra

Sensory and Volatile Profiles of Monovarietal North Tunisian Extra Virgin Olive Oils from ‘Chétoui’ Cultivar Faten Essid1, 3, 4,＊ , Samira Sifi1, Gabriel Beltrán2, Sebastián Sánchez3 and Aly Raïes4 1 Laboratory of Tunisian Board of Olive Oil (ONH) (10, Avenue Mohammed V, 1001 Tunis, TUNISIA) 2 Center IFAPA (Venta del Llano, 23620 Mengibar, Jaén, SPAIN) 3 ‌Research Group “Bioprocesses (TEP-138, ‘Junta de Andalucía’) Department of Chemical, Environmental and Materials Engineering, Jaén University (Paraje Las Lagunillas, 23071 Jaén, SPAIN) 4 ‌Laboratory of Micro-organisms and Active Bio-molecules (LR03ES03) Department of Biology, Faculty of Science of Tunis, Tunis El Manar University (2092 El Manar II, Tunis, TUNISIA)

Abstract: The quality of olive oil is defined as a combination of characteristics that significantly determine its acceptance by consumers. This study was carried out to compare sensorial and chemical characteristics of sixty ‘Chétoui’ extra virgin olive oils (EVOOc) samples from six northern areas in Tunisia (Tebourba (EVOOT); Other regions (EVOON): Mornag, Sidi Amor, El Kef, Béjà and Jendouba). Trained panel taste detected ten sensory attributes. EVOOT and EVOON were defined by ‘tomato’ and ‘grass/ leave notes, respectively. Twenty one volatile compounds from EVOOc were extracted and identified by Headspace Solid-Phase Microextraction followed by Gas Chromatography- Flame Ionization Detector. Principal component and cluster analysis of all studied parameters showed that EVOOT differed from EVOON. Sensory and volatile profiles of EVOOc revealed that the perception of different aromas, in monovarietal olive oil, was the result of synergic effect of oils’ various components, whose composition was influenced by the geographical growing area.

Key words: geographical‌ effect, ‘Chétoui’ from Tebourba, sensory proprieties, sensory evaluation index (SE), volatile compounds

1 INTRODUCTION In fact, VOO is characterized by a unique flavor, which rep- Olive oil has been used for thousands of years in the resents one of the most important qualitative aspects of countries surrounding the Mediterranean Sea. The dynamic this vegetable oil, and plays a major role in consumer ap- increase on the demand for Virgin Olive Oils（VOO）cannot proval. A full description of the organoleptic characteristics only be explained by their health properties, but also by of the oil is only obtainable through sensory analysis. More- their organoleptic properties1）. The fine flavor（aroma and over, the quali-quantitative determination of the volatile taste）and color of VOO distinguish it from other edible compounds can provide very useful information on product vegetable oils, giving it a superior quality that is tradition- quality. ally appreciated by the consumers in Mediterranean coun- Volatiles mainly contribute to the flavor（smell and tries and now all over the world. Nowadays the quality of taste）, and are the principal components responsible for olive oil reflects nutritional, sensory and commercial the positive fruity attribute, characteristic of the oil from aspects and is regulated by European legislation（EC）, the healthy, fresh fruits, both ripe or unripe2）. Recent works International Olive Council（IOC）and also the Codex Ali- reviewed the several factors influencing aromatic quality of mentarius. Aroma and taste are the only parameters that VOO, i.e. biogenesis and composition of volatiles, relation- consumers can appraise directly, while other quality ships with sensory notes, possible influence of agronomic features（e.g. chemical composition）are not always labelled and processing factors, and oil oxidation3, 4）. Other re- on the bottle. searchers found that the different volatile composition in Sensory characteristics are used to define VOO quality. four Tunisian oils was affected by the cultivar, showing also

＊Correspondence to: Faten Essid, Laboratory of Micro-organisms and Active Bio-molecules (LR03ES03) Department of Biology, Faculty of Science of Tunis, Tunis El Manar University 2092 El Manar II, Tunis, TUNISIA E-mail: [email protected] Accepted March 14, 2016 (received for review December 26, 2015) Journal of Oleo Science ISSN 1345-8957 print / ISSN 1347-3352 online http://www.jstage.jst.go.jp/browse/jos/ http://mc.manusriptcentral.com/jjocs

533 F. Essid, S. Sifi and G. Beltrán et al.

a close relation to the enzymatic profiling that is genetically EVOOc from Tebourba and other five north Tunisian determined5）. In 2007, other peculiar differences in the regions. composition of volatile in Tunisian and French from Pro- The work described here constitute another step which, tected Designation of Origin（PDO）oils were found6） dem- also, contributes to the establishment of PGI for Tebourba onstrating that the building up of metabolites in oils from EVOO throw the study of volatile profiles and sensory different cultivars was related to genetic origin. Different notes of oils produced in this region. A deep evaluation studies on chemical composition of extra virgin olive oils remains necessary to demonstrate the singularity of （EVOO）revealed, also, the influence of growing areas7）. So, EVOOc from Tebourba and differentiate it from others the olive production area is greatly responsible for the spe- EVOOc produced outside Tebourba regions. cific characteristics of olive oil. Over the past decades, there has been an increasing interest in the geographical identification of EVOO, as a reliable criterion for its quality and authentication. As far as this point is concerned, there 2 MATERIALS AND METHODS has been a remarkable proliferation of research works 2.1 Oils samples focused on the development of suitable methods（chro- Sixty samples of EVOOc from different regions from the matographic, spectroscopic/ spectrometric and DNA- north of Tunisia（Tebourba（EVOOT）; North（EVOON）: based techniques）to classify and discriminate among olive Mornag, Sidi Amor, El Kef, Béjà and Jendouba）and produc- oils from different geographical origins8－10）. Others have ers were used in this research. Over the olive crop seasons conducted studies in order to establish geographical origin from 2010 / 2011 to 2013/ 2014, olive fruits（Olea europaea of the selected olive oils（‘ Picholine marocaine’） by the as- L.）were harvested at the same ripeness stage with the Rip- sessment of different chemical components as geographical ening Index 2.90 and transformed into oil within 24 h in a markers in combination with chemometric tools11）. modern mill. The oils samples were analyzed as soon as Olive oil is Tunisia’s main agricultural export, accounting they arrived to the lab. for about 60％, and has a fundamental importance for the country, employing within the sector about a million indi- 2.2 Free acidity, peroxide value and UV spectrophotomet- rectly. Tunisia’s diverse olive varieties and cultivation ric indice systems are categorized by region. In the north, 100 feet Free acidity（FA）, expressed as percent of oleic acid（％ per hectare of land is principally planted with‘ Chétoui’, C18:1）, peroxide value（PV）, given as milliequivalents of －1 ‘Sayali’ and‘ Jarboui’ olive trees. In the center of the active oxygen per kilogram of oil（meq. O2. kg ）and UV

country, on 50-60 feet per hectare are cultivated‘ Chemla- absorption characteristic at 270 nm（K270）were determined li’ and‘ Ouslati’. The south consists of 17 feet per hectare according to the method of the Official Journal of the Eu- of Zalmati, Zarrazi, and Chemlali12）. Over the olive crop ropean Communities13）. season from 2014 to 2015, olive oil production in Tunisia has increased fourfold, making it the second largest pro- 2.3 Sensory characterization ducer after Spain. However, the challenge for Tunisia’s In the case of the characterization/valorization of mon- olive oil industry is not just to find way to increase produc- ovarietal, protected designation of origin（PDO）and pro- tion but also to export less oil in bulk and more bottled and tected geographical indication（PGI）14, 15）, it is firstly neces- branded products. More than 75％ of the country’s output sary to verify that the sample has the characteristics is exported in bulk to Italy and Spain, where it is mixed provided in the extra virgin category using current with local oil before being bottled and marked as a product methods2）, and to subsequently analyze it according to the of those countries. old profile sheet13） to verify the presence of characteristic In the context of improving olive oil quality, since 2010, descriptors. The sensory characterization was performed the Quality Department in the Tunisian Olive Oil Board has by a fully trained analytical taste panel, composed of eight set a goal of establishing Protected Geographical Indication assessors, members of staff of“ the Tunisian Board of Olive （PGI）labeled products.‘ Chétoui’ extra virgin olive oils Oil”（ ONH）. Each taster observed, smelled and tasted the （EVOOc）from Tebourba region were chosen thanks to its oil under consideration in order to access the visual, olfac- particular fatty acids composition and specific flavor. tory, gustatory and tactile or kinesthetic sensations. Therefore, the aim of this research study was to perform a Knowing that samples have the same color（green）, ten at- physicochemical and compositional characterization of Te- tributes were evaluated: seven during olfactory phase bourba olive oil as well as to determine its sensorial propri- （fruity green/ ripe, grass/leave, tomato, artichoke, almond, eties. Collaborating with Jaén University, some data are apple and banana）, and three during the gustatory phase already available concerning this oil overall composition （bitter, astringent and pungent）. Attributes were assessed and quality, demonstrating the possibility of using phenolic on an oriented 10 cm line scale and quantified measuring compounds as «authentic markers» to discriminate among the location of the mark from the origin. The data obtained

534 J. Oleo Sci. 65, (7) 533-542 (2016) Sensory and volatile profiles of ‘Chétoui’ extra virgin olive oils

for the 10 descriptors were used to define the sensory supplied by S.A. Perlarom（Louvaine-La-Neuve, Belgium）. profile for each sample（average values and their standard Compounds such as（E）-hex-3-enal,（ Z）-hex-2-enal,（ Z） deviations）. The quantitative sensory evaluation（SE）was -pent-2-enal, and pentene dimers were tentatively identi- the final global score attributed to each sample and ranged fied on the basis of mass spectra and their concentrations from 0 - 10. approximately quantified according to their available isomers. The 13-hydroperoxide derivatives from LA（13- 2.4 Overall Quality Index HPOD）and LnA（13-HPOT）were prepared using soybean The Overall Quality Index（OQI）introduced by the Inter- LOX. All chemicals used as standards and solvents had national Olive Council16） was used to express EVOO quality purity up to 99.0％. All the SPME operations were auto- numerically. The scale ranges from 0 to 10 and considers 4 mated using a Combi Pal AutoSampler Varian（Walnut

quality parameters: the score of SE, FA, K270 and PV ac- Creek, CA, USA）. cording to the following equation: 2.6 Statistical analysis OQI 2.55 0.91 SE 0.78 FA 7.35 0.066 PV ＝＋－－ K270－ All parameters were determined in triplicate for each sample. Analysis of variance（ANOVA）was applied in order 2.5 Extraction of the volatile compounds to evaluate the influence of growing area conditions on Volatile fractions of the extra-virgin olive oils were ana- ‘Chétoui’ olive oil（SPSS statistical package（Version 18.0 lyzed according to a modified method17）. Solid-phase mi- for Windows, SPSS Inc. Chicago, IL, 2009）.The results are croextraction（SPME）followed by GC-FID were used. Olive reported as mean values and standard deviations. Signifi- oil samples were conditioned to room temperature and cant differences among cultivars were determined by anal- then placed in a vial heater at 40℃. After 10 min of equilib- ysis of variance using a Duncan’s multiple tests. Differences rium time, volatile compounds from headspace were ad- were considered statistically significant when probability sorbed on a SPME fiber DVB/ Carboxen/ PDMS 50/ 30 μm was greater than 99％（ p＜0.01）. Pearson’s correlation（r）（Supelco Co., Bellefonte, PA）. Sampling time was 50 min was calculated in order to find relations between sensory at 40℃. Desorption of volatile compounds trapped in the attributes and volatile compounds. Principal components SPME fiber was done directly into the GC injector. Volatiles analysis（PCA）was applied to quality parameters, chemical were analyzed three times in duplicate experiments using and sensory data. PCAs were carried out for all raw data a HP-6890 gas chromatograph equipped with a DB-Wax processed with a cross-validation method. Hierarchical capillary column（60 m×0.25 mm i.d., film thickness＝0.25 cluster analysis（HCA）was used to obtain a dendrogram. μm; J&W Scientific, Folsom, CA）. Operating conditions Data were clustered by hierarchical complete-linkage clus-

were as follows: N2 as carrier gas; injector and detector at tering and squared Euclidean distance. 250℃; column held for 6 min at 40℃ and then pro- grammed at 2℃ min－1 to 128℃. Quantification was performed using individual calibration curves for each identified compound by adding known amounts of different 3 RESULTS AND DISCUSSION compounds to redeodorized high-oleic sunflower oil. Com- 3.1 Physiochemical parameters

pound identification was carried out on a HRGC-MS Fisons The physicochemical quality parameters（FA, K270 and series 8000 equipped with a similar stationary phase PV）of olive oils from the studied cultivars are represented column and two different lengths, 30 and 60 m, matching in Table 1. All the analyzed oils showed very low values for against the Wiley/ NBS Library, and by GC retention time the regulated physicochemical parameters valuated（FA ≤ －1 against standards（Kovats indices are given in brackets）: 0.8％, K270 ≤ 0.220 and PV ≤ 20 meq. O2. Kg ）. All of them （E）-hex-3-enal［1137］,（ Z）-hex-3-enal［1156］,（ Z）-hex-2- belonged to the ranges established for“ extra virgin olive enal［1218］,（ E）-hex-2-enal［1233］,（ E）-hex-3-enol［1364］, oil”（ EVOO）category, as required by the European Com- （Z）-hex-3-enol［1383］,（ E）-hex-2-enol［1399］, hexanal munity Regulation13）. No significant differences（p＞0.01）［1074］, hexan-1-ol［1355］, pent-1-en-3-one［1018］,（ Z） were detected on these parameters from an area to -pent-2-enal［1100］,（ E）-pent-2-enal［1127］,（ E）-pent-2- another. These results were consistent with the findings of en-1-ol［1322］,（ Z）-pent-2-en-1-ol［1327］, pent-1-en-3-ol other authors18）. They reported that, cultivar or origin area ［1168］, pentanal［980］, pentan-1-ol［1261］, hexyl acetate had no significant influence on these analytical parameters. ［1293］,（ Z）-hex-3-en-1-yl acetate［1316］,（ E）-hex-2-en-1- However olive fly attacks, improper systems of harvesting, yl acetate［1337］ and ethyl hexanoate［1249］. carriage and storage of olives, and technological treatments Linoleic acid（LA）, linolenic acid（LnA）, soybean lipoxy- may favor the hydrolysis of triglycerides which will increase genase（LOX）, and reference compounds used for volatile free fatty acid concentration and have the most influence identification were supplied by Sigma-Aldrich（St. Louis, on quality parameters19）. MO, USA）except for（Z）-hex-3-enal, which was generously Oils from different areas presented significant differenc-

535 J. Oleo Sci. 65, (7) 533-542 (2016) F. Essid, S. Sifi and G. Beltrán et al.

Table 1 Physiochemical parameters and sensory evaluation of analyzed oils obtained from olives fruits grown in different areas.

Tebourba North Areas Range Range Parameters Mean Min Max Mean Min Max FA (% C18:1) 0.29 ±0.09 a 0.18 0.38 0.38 ±0.11 a 0.23 0.61 a a K270 0.186±0.018 0.159 0.210 0.197±0.017 0.164 0.220 –1 a a PV (meq.O2. kg ) 9.60 ±1.35 5.00 12.60 10.54 ±2.85 5.00 15.00 SE 7.83 ±0.38 a 7.28 8.46 7.49 ±0.22 a 7.10 8.07 OQI 7.54 ±0.04 a 7.45 7.57 6.80 ±0.14 b 6.64 6.92 Means within a row for each parameter marked with different lowercase letter (a and b) are significantly different (p < 0.01).

Note: FA - free acidity expressed as percent of oleic acid; K270 - UV absorption characteristic at 270 nm; PV - peroxide value expressed as milliequivalents of active oxygen per kilogram of oil; SE - sensory evaluation ranged from 0 to 10; OQI - overall quality index ranged from 0 to 10.

es（p＜0.01）in OQI（Table 1）. The highest mean value was ‘Grossane’,‘ Picholine’,‘ Verdale des Bouches du Rhône’, detected in EVOOT（7.54）which highlighted the quality of ‘Ribiére’,‘ Sabine’,‘ Saurine’,‘ Sigoise’ and‘ Triparde’. Tebourba analyzed oils. Whereas, RDO from C is made up of:‘ Calletier’,‘ Araban’, The large variability in monovarietal oils sensory charac- ‘Blanquetier’, Blavet’,‘ Nostral’ and‘ Ribeyrou’. The ob- teristics according to geographical growing areas was tained results from sensory characterization showed that noted. The maximum panel test score obtained was for the intensities of the three positive descriptors（fruity, EVOOT. SE mean value was 7.83（Table 1）. This result was bitter and pungent）varied from one harvest to another. consistent with the existence of an obvious correlation RDO from PA showed higher levels of fruity, bitter and between OQI and SE. pungent than RDO from C. The first fruity analogical de- scriptor for RDO from PA, the most often cited by tasters, 3.2 Sensory analysis was‘ artichoke’. In the case of RDO from C, the olive oils Sensory profiles of oils samples were represented in Fig. were characterized by high intensity of‘ fresh almond’ 1. Descriptors perceived in all studied samples were note. This research made on French oils demonstrates ‘fruity’,‘ grass/ leave’,‘ tomato’,‘ artichoke’,‘ almond’, that, even, olive oils produced in the same area（Provence- ‘astringent’,‘ apple’,‘ banana’,‘ bitter’ and‘ pungent’. The Alpes-Côte d’Azur）from different varieties present differ- perception of‘ fruity’,‘ bitter’,‘ artichoke’ and‘ tomato’ ent sensory characteristics, so different flavors. In this reached the highest level in EVOOT（Fig. 1a）: 7.9, 4.2, 3.8 sense, another study was carried22）, in Italy, in order to and 6.4, respectively. However, EVOON（Fig. 1b）presented demonstrate variety influence on virgin oil flavor. The re- a high level in‘ grass/ leave’ note（4.2）. Sensory profiles of search was made, for 4 years, on oil samples obtained from EVOOT and EVOON revealed that the perception of differ- 18（‘ Baia’,‘ Casaliva 1’,‘ Casaliva 2’,‘ Cornarol’,‘ Favarol’, ent notes and aromas was the result of the synergic effect ‘Frantoio’,‘ Gargnà’,‘ Grignano’,‘ Leccino’,‘ Less’, of the oils’ various components, whose composition was in- ‘Maurino’,‘ Miniol’,‘ Mitria’,‘ Pendolino’,‘ Raza’,‘ Regina’, fluenced by the geographical growing area7）, so genetic ‘Rossanello’ and‘ Trepp’） cultivars grown in the same factor. The influence of this parameter on the variation of orchard in the western coast of the Garda Lake（northern the flavor of‘ Chétoui’ olive oils was also highlighted by Italy）. The obtained results showed that the aromatic Tunisian authors20）. Other authors focused on flavors of quality of virgin olive oil depends on genetic factor. olive oils from different cultivars but produced in the same area21）. They investigated on differentiation of French 3.3 Aromatic compounds virgin olive oil RDOs by sensory characteristics. The The aim of increasing the quality standards for VOO is samples were from two regions: Rhône-Alpes（Nyons）and continuously stimulating the study of biochemical path- Provence-Alpes-Côte d’Azur（Vallée des Baux de Provence ways related to organoleptic properties and the develop- （VB）, Haute de Provence（A）, Aix-en-Provence（PA）and ment of technological procedures to improve them. Volatile Nice（C））.The RDOs from Provence-Alpes-Côte d’Azur are compounds are low-molecular weight compounds（less made up of primary and secondary varieties, as well as than 300 Da）that vaporize readily at room temperature23）. local and old varieties. For example, RDO from PA is made The major volatile compounds, usually found in extra virgin up of:‘ Aglandau’,‘ Cayanne’,‘ Salonenque’,‘ Bouteillan’, olive oil of high sensory quality, are the C5 and the C6 vola-

536 J. Oleo Sci. 65, (7) 533-542 (2016) Sensory and volatile profiles of ‘Chétoui’ extra virgin olive oils

method was established to determinate volatile compositions of olive oils. Therefore, in this study, the extraction of volatile compounds from oil samples was done by the modified method to detect, mainly, the aromatic components on C5 and C6 from LA and LnA. Headspace solid-phase microextraction（SPME）followed by GC-FID were used to characterize the EVOOc volatile fractions. The detection of aroma volatile compounds emitted by EVOO was important for quality control of this product. Twenty one volatile compounds were identified in Fig. 2. （E）-hex-2-enal represented a main compound extracted from all examined samples. The means values for EVOOT and EVOON were respectively 13.4 and 9.4 mg / kg. Some researchers found that（E）-hex-2-enal was the dominant volatile in‘ Chétoui’ oils profiles7）. This compound could be, also, considered the main contributor to green, fruity, bitter and astringent attributes27）. The other identified compounds were mainly（E）-hex-3- enol,（ E）-hex-2-enol,（ E）-pent-2-enal,（ Z）-hex-3-enol, （Z）-pent-2-en-1-ol, hexanal and hexan-1-ol. The contents of（E）-hex-3-enol and（E）-pent-2-enal varied widely according to the production area. Tebourba oils showed the highest means values in（E）-hex-3-enol and（E）-pent-2- enal 6.2 and 3.7 mg/ kg, respectively, whereas samples from the north recorded the lowest means values 3.2 and 1.3 mg / kg, respectively. The highest means values of（Z）-pent-2-en-1-ol,（ E） -hex-2-enol and hexan-1-ol were found in Tebourba oils increasing their proportion in C5 and C6 alcohols（Fig. 2）. EVOON were more rich than EVOOT in（Z）-hex-3-enol and hexanal. In overall quality of olive oil, the aroma plays an important role in directing consumer preference so it is important to determine, at least, the relative amounts of the aroma components of olive oils. Unfortunately, the unique and delicate EVOO flavor depends on the interaction of hundreds of compounds: aldehydes, alcohols, esters, hy- drocarbons, ketones, furans and others28）. Fig. 1 Sensory profiles of extra virgin olive oils from ‘Chétoui’ cultivars grown in Tebourba（a）, the To characterize aroma profiles of studied oils, all identi- other studied regions of the north of Tunisia（b）. fied components（Fig. 2）were regrouped in aldehydes, alcohols, esters and ketone. Means and boxplots for each tile compound24）. In this sense, the group of researchers in monovarietal oils were represented in Fig. 3. Standardiza- center IFAPA established the participation of the lipoxy- tion of all values to mean zero and unit variance was neces- genase（LOX）pathway in the biosynthesis of compounds of sary to display them on the same graph, enabling a helpful five and six straight-chain carbons（C5 and C6 compounds） visualization of apparent differences and/ or similarities in the olive oil volatile fraction. C6 compounds are synthe- between groups. sized from polyunsaturated fatty acids containing （a Z,Z） C5（Pentanal,（ Z）-pent-2-enal and（E）-pent-2-enal）and -1,4-pentadiene structure such as linoleic（LA）and linolenic C6（Hexanal,（ E）-hex-3-enal,（ Z）-hex-3-enal,（ Z）-hex-2- （LnA）acids. However, C5 compounds would be generated enal and（E）-hex-2-enal）aldehydes were the major fraction through an additional branch of the LOX pathway. In previ- in‘ Chétoui’ analyzed oils profiles. The highest content was ous works carried out by the same group（published for recorded in EVOOT（49.38％）. However, in EVOON, alde- ‘Arbequina’ and‘ Picual’25, 26） and no published data for hydes represented 47.72％. The contribution of these com- ‘Chétoui’） According to the obtained results a modified ponents is crucial to olive oil quality and is related to posi-

537 J. Oleo Sci. 65, (7) 533-542 (2016) F. Essid, S. Sifi and G. Beltrán et al.

Fig. 2 V olatile contents in‘ Chétoui’ extra virgin olive oils produced in Tebourba and different geographical areas from the north of Tunisia.

（Pent-1-en-3-ol, Pentan-1-ol,（ E）-pent-2-en-1-ol and（Z） -pent-2-en-1-ol）and C6（Hexan-1-ol,（ E）-hex-3-enol,（ Z） -hex-3-enol and（E）-hex-2-enol）identified alcohols were abundant. As well known, C6 alcohols are derived from the lipoxygenase（LOX）pathway that involves a series of enzymes that oxidize, cleave（hydroperoxide lyase, HPL） and are reduced to alcohols（alcohol dehydrogenase, ADH）4）. The minor fractions in‘ Chétoui’ analyzed oils profiles were esters（Etyl hexanoate, hexyl acetate,（ Z）-hex-3-en- 1-yl acetate and（E）-hex-2-en-1-yl acetate）ranged between 2.37 and 6.89％, and ketone（pent-1-en-3-one）ranged between 1.02 and 1.62％. Esters are considered as important constituents of many fruits and linked to the positive fruity aroma of olive oil. Generally, the formation of volatile esters involves the alcohol acetyl transferase action. The presence of ketone in the aroma profile in EVOOc was Fig. 3 P rofiles of volatile compounds（％）of extra virgin probably related to the activity of indigenous microflora in olive oils from‘ Chétoui’ cultivar grown in the fruit. C5 Ketones are generally linked to positive Tebourba and selected regions from the north of sensory characteristics and proposed as markers of virgin Tunisia. olive oil quality30）. These results are in concordance those obtained by Tu- tive attributes and flavors. Aldehydes are usually nisian researchers20）. They focused on the variation of vola- characterized by intense sensory descriptions associated tile compounds profiles of‘ Chétoui’ olive oils induced by with green, fruity and bitter sensory notes29）. growing area. The olives from‘ Chétoui’ cultivar were col- Alcohols fraction were also important in EVOOc studied lected in 14 different Tunisian regions: Amdoun, Testour, samples, in a range between 44.07％ and 45.81％. C5 Bouarada, Goubellat, Lakouet, Gaafour, Amayem, Chuigui,

538 J. Oleo Sci. 65, (7) 533-542 (2016) Sensory and volatile profiles of ‘Chétoui’ extra virgin olive oils

Slouguia, Elles, Sers, Borj El Amri, Jendouba, Zaghouan. Table 2 Linear correlations among oils sensory notes and The extraction of olive oils was processed by the laboratory aromatic chemical compounds. mill. The application of SPME to analysis of virgin oil head- Sensory descriptors Volatile compounds r ρ space allowed the detection of significant differences in the proportions of volatile constituents from oils of various Fruity (E)-hex-3-enal 0.804 0.000 geographical origins. This would probably affect olive oils Hexan-1-ol 0.692 0.000 flavors. As the harvesting period and extraction conditions Hexyl acetate 0.669 0.003 were similar for all studied samples, the results indicate Grass/leave (Z)-hex-3-enol 0.891 0.002 that genetic factor and environmental conditions influence the volatile production. (E)-pent-2-en-1-ol 0.766 0.000 After assessing the chemical and sensorial characteris- (E)-hex-3-enal 0.717 0.000 tics of monovarietal olive oils, some considerations could Tomato (E)-pent-2-enal 0.978 0.000 be drawn about correlations between volatile compounds Hexan-1-ol 0.674 0.002 and sensorial attributes（Table 2）. For the olfactory descriptors,‘ grass/leave’ note was, es- Pent-1-en-3-one 0.534 0.003 pecially, correlated with（Z）-hex-3-enol（r＝0.0891）which Artichoke (E)-hex-3-enal 0.822 0.000 explains the dominance of‘ green’ note in EVOON. (Z)-hex-3-enal 0.812 0.001 However,‘ tomato’ note was, especially, correlated to（E） (E)-hex-2-enal 0.687 0.005 -pent-2-enal（r＝0.978）. Therefore, this note characterized Almond (E)-pent-2-enal 0.665 0.000 EVOOT.‘ Fruity’,‘ artichoke’,‘ almond’,‘ apple’ and ‘banana’ notes were, mainly, correlated to（E）-hex-3-enal (Z)-pent-2-en-1-ol 0.613 0.004 （r＝0.804）,（ E）-hex-3-enal（r＝0.822）,（ E）-pent-2-enal（r Pent-1-en-3-one 0.660 0.001 ＝0.665）, hexanal（r＝0.683）and hexan-1-ol（r＝0.862）; re- Astringent (E)-hex-2-enal 0.658 0.000 spectively. (E)-hex-3-enol 0.603 0.000 The’ taste’ notes of‘ astringent’,‘ bitter’ and‘ pungent’ were, mainly, correlated to（E）-hex-2-enal（r＝0.658）, (E)-hex-2-enol 0.547 0.002 pent-1-en-3-one（r＝0.814）and pentan-1-ol（r＝0.833）; re- Apple Hexanal 0.683 0.000 spectively. (Z)-hex-3-enol 0.539 0.002 In this way, many correspondences were found between (E)-pent-2-enal 0.512 0.005 sensory notes and chemical compounds, most of them in agreement with the literature3, 4, 31, 32）. Banana Hexan-1-ol 0.862 0.000 Most of the volatile showed an average content higher (Z)-pent-2-en-1-ol 0.800 0.000 than odor and taste thresholds, explaining the correlations Hexanal 0.745 0.002 to sensory attributes. Other volatile compounds, correlated Bitter Pent-1-en-3-one 0.814 0.001 to sensory attributes, showed concentrations different from odor and taste thresholds: pentan-3-one had content (E)-pent-2-enal 0.736 0.000 lower than odor threshold;（ E）-pent-2-anal showed con- (E)-hex-3-enol 0.608 0.004 centration higher than odor, but smaller than taste thresh- Pungent Pentan-1-ol 0.833 0.000 old. Pent-1-en-3-one 0.828 0.000 Some volatiles were correlated to the sensory notes even Pent-1-en-3-ol 0.779 0.001 if their concentration was smaller than a given thresholds. This could be due to a synergic effect with other com- Significant correlation at ρ < 0.01. pounds for that specific sensory note. The odor threshold is possibly more effective than that taste. order to detect important variables, a two-dimensional The application of PCA algorithm to all collected data scatter plot of loadings for the first two components from from olive oils samples showed two distinctive groups. The PCA was represented in Fig. 4b. The first two factors were bi-plot graph for the Scores（Fig. 4a）and Loadings（Fig. 4b） sufficient to account for 93.48％ of the total（PC-1: 70.97％; were obtained. PC- 2: 22.51％. If the two graphs in Fig. 4 were compared, The data distribution shown on the Scores graph（Fig. we observed that OQI; pentanal;（ E）-hex-3-enol;（ E）-pent- 4a）represented the influence of the geographical area on 2-enal; tomato; fruity; banana; pentan-1-ol; almond;（ E） PC1. Thus, oils obtained from Tebourba were distributed -hex-2-enol; hexan-1-ol;（ E）-hex-2-enal; apple, hexyl on the top side of the graph, while the oils obtained from acetate; artichoke; bitter; SE;（ E）-hexyl-2-en-1-yl acetate; North of Tunisia（Sidi Amor, Mornag, Béjà, Jendouba and El pungent;（ Z）-pent-2-enal; pent-1-en-3ol and（Z）-pent-2- Kef）were distributed on the bottom side of the graph. In en-1-ol were correlated with oils obtained from Tebourba,

539 J. Oleo Sci. 65, (7) 533-542 (2016) F. Essid, S. Sifi and G. Beltrán et al.

Fig. 5 Dendrogram of cluster analysis for the different geographical areas.

4 CONCLUSIONS The current study demonstrated the influence of geographical origin of Tunisian‘ Chétoui’ extra virgin olive oils on their sensory and volatile profiles. Sensory characterization of‘ Chétoui’ oils samples leaded to the perception of ten sensory attributes. EVOOT presented high levels of ‘fruity’ and‘ tomato’ notes. Whereas, EVOON presented a high level of‘ grass/leave’ note. In terms of chemical composition, the aliphatic C6 compounds were the major volatile components detected in EVOOc. Concentrations of each C5 or/ and C6 compound changed from one sample to another according to olive oils origins. These quantitative differences could notably modify the sensory perceptions Fig. 4 Principal Components Analysis（PCA）model obtained for the different geographical areas: on oils. In fact, calculating Pearson’s correlation revealed Scores plot（a）and Loadings plot（b）. The biggest that the high content on（E）-pent-2-enal was responsible on a perception of a high note of tomato in EVOOT dark spots（●）indicate the barycenter of each ‘ ’ group. whereas a high content（Z）-hex-3-enol was responsible on a perception of a high note of‘ green grass’ on EVOON. while PV; K270; FA;（ Z）-hex-2-enal; astringent;（ Z）-hex3- Chemometric evaluation of data, obtained through Panel en-1-yl acetate;（ Z）-hex-3-enal;hexanal; grass/ leave;（ E） test evaluation and headspace analysis, showed a correla- -pent-2-en-1-ol; pent-1-en-3-one; etyl hexanoate and（Z） tion between oils aroma and olives growing areas. On the -hex-3-enolwere correlated with oils obtained from the basis of the results, EVOOc were divided into two separat- north of Tunisia. So, the PCA applied to all collected data ed groups. EVOOT were classified as fruity oils, while the gave very good results showing high positive correlation majority of EVOON were classified as oils with green pro- between oils from Tebourba and fruity properties while oils prieties. With the obtained results, it is possible to conclude from surrounding regions seem correlated with green pro- that Tebourba region seems to produce olive oils with high prieties. These results were consistent with those obtained physico-chemical standards of quality and particular in Fig. 2 and Table 2. sensory proprieties. Similarly, HCA was performed to detect the influence of geographical areas on potential sample clustering（Fig. 5）. The dendrogram indicated that, at rescaled distance of twenty, samples were clustered into two groups by geo- ACKNOWLEDGMENT graphical areas: Tebourba and North of Tunisia（Sidi Amor, The authors gratefully acknowledge the Ministry of Mornag, Béja, Jendouba and El Kef）. Higher Education, Scientific Research and Technology of

540 J. Oleo Sci. 65, (7) 533-542 (2016) Sensory and volatile profiles of ‘Chétoui’ extra virgin olive oils

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