**3.1 FAMEs analysis**

VOOs under investigation showed the typical profile of fatty acids of the areas of production. In general, the oils were dominated by palmitic acid (C16: 0), stearic acid (C18: 0), oleic acid (C18: 1) and linoleic acid (C18: 2). The observed values do not show a particular pattern that can indicate the mode of extraction and the type of packing. It is well known, in fact, that fatty acids are dependent on genetic factors, soil and climate (Christie, 1998; Dabbou, et al., 2010; Gharsallaoui, et al., 2011; Manai, et al., 2007).

Volatile and Non-Volatile Compounds of Single Cultivar Virgin Olive Oils Produced

MCounts RIC all c98c.s ms

kCounts RIC all c 98c.sms

kCounts RIC all c 98c.sms

82.289 min 6.321 min 6.507 min6.654 min

**3.3 SPME-GC/MS and sensory analysis** 

 

> 0.00 0.25 0.50 0.75 1.00 1.25

500

100

50

55.722 min

100

150

200

17.844 min 18.126 min 18.965 min 19.476 min

20.878 min 21.196 min

61.929 min

65.526 min 68.848 min

69.108 min 71.843 min 74.423 min 77.521 min 79.918 min 80.803 min

21.794 min 22.420 min

200

300

400

2.566 min 2.943 min 3.284 min 3.509 min 3.702 min

> 22.712 min 24.051 min

4.441 min 4.887 min 5.284 min 5.505 min

> 25.219 min 26.382 min 27.750 min 29.411 min 31.233 min 32.331 min 32.997 min 34.517 min

in Italy and Tunisia with Regard to Different Extraction Systems and Storage Conditions 9

Cultivar and extraction systems have a considerable effect on sensory attributes of virgin olive oil. A typical mass chromatogram of the volatile component of one of the analyzed sample is reported in Fig. 4, while the bar chart of Fig. 5 shows the distribution of volatile compounds at five and six carbon atoms that mostly contribute to the olive oil aroma.

2.5 5.0 7.5 10.0 12.5 minutes

35.250 min

> 35.715 min 36.179 min

9.469 min

10.312 min

10.592 min

11.846 min

45.771 min

12.591 min

9.583 min

> 39.533 min 40.127 min 40.547 min 41.311 min

104.272 min 105.105 min 43.413 min

44.245 min

125.572 min

Fig. 4. A typical chromatogram of volatile compounds of one of the analysed samples.

84.904 min 85.519 min

In fact, these systems can produce olive oils with better organoleptic profiles.

According to the five markers selected as active components of the SPME-GS/MS chromatograms (see paragraph 2.2.5), the distinction of the VOOs under investigation was allowed. Even if both Italian and Tunisian oils were fruity with bitter and pungent characteristics, VOOs of Coratina Cv showed an higher values of fruitiness and bitterness intensity with a clear pungency mainly when they were extracted in centrifugation systems.

60 70 80 90 100 110 120 minutes 130

<sup>20</sup> <sup>25</sup> <sup>30</sup> <sup>35</sup> <sup>40</sup> <sup>45</sup> minutes <sup>0</sup>

#### **3.2 Quality parameters**

The extraction system has a significant effect on the physical and chemical parameters of the oil: the pressure system can preserve well the colour and the antioxidants of the olive oil, but may affect negatively the sensory profile. From the results obtained, olive oils were characterised by significant differences in free acidity and phenol content (Figures 2 and 3).

Fig. 2. Box plot of Tunisian VOOs. Free acidity is plotted vs the extraction system.

Fig. 3. Box plot of Tunisian VOOs. Total phenols are plotted vs the extraction system.

In general, oils produced with the pressure system have higher free acidity levels than the same oils produced by centrifugation (2P and 3P) and sometime cannot be classified as Extra Virgin Olive Oil (Fig. 2). Moreover, they are often characterised by a lower content of phenols (Fig. 3). In a similar way, the peroxide and K232 and K270 extintion coefficient values were higher than the same oils produced by centrifugation methods.

#### **3.3 SPME-GC/MS and sensory analysis**

8 Olive Oil – Constituents, Quality, Health Properties and Bioconversions

The extraction system has a significant effect on the physical and chemical parameters of the oil: the pressure system can preserve well the colour and the antioxidants of the olive oil, but may affect negatively the sensory profile. From the results obtained, olive oils were characterised by significant differences in free acidity and phenol content (Figures 2 and 3).

Fig. 2. Box plot of Tunisian VOOs. Free acidity is plotted vs the extraction system.

Fig. 3. Box plot of Tunisian VOOs. Total phenols are plotted vs the extraction system.

values were higher than the same oils produced by centrifugation methods.

In general, oils produced with the pressure system have higher free acidity levels than the same oils produced by centrifugation (2P and 3P) and sometime cannot be classified as Extra Virgin Olive Oil (Fig. 2). Moreover, they are often characterised by a lower content of phenols (Fig. 3). In a similar way, the peroxide and K232 and K270 extintion coefficient

**3.2 Quality parameters** 

Cultivar and extraction systems have a considerable effect on sensory attributes of virgin olive oil. A typical mass chromatogram of the volatile component of one of the analyzed sample is reported in Fig. 4, while the bar chart of Fig. 5 shows the distribution of volatile compounds at five and six carbon atoms that mostly contribute to the olive oil aroma.

Fig. 4. A typical chromatogram of volatile compounds of one of the analysed samples.

According to the five markers selected as active components of the SPME-GS/MS chromatograms (see paragraph 2.2.5), the distinction of the VOOs under investigation was allowed. Even if both Italian and Tunisian oils were fruity with bitter and pungent characteristics, VOOs of Coratina Cv showed an higher values of fruitiness and bitterness intensity with a clear pungency mainly when they were extracted in centrifugation systems. In fact, these systems can produce olive oils with better organoleptic profiles.

Volatile and Non-Volatile Compounds of Single Cultivar Virgin Olive Oils Produced

in Italy and Tunisia with Regard to Different Extraction Systems and Storage Conditions 11

Fig. 7. Biplot of 1.hexanol at 95% confidence level. The genotype was the main factor considered. The Cvs under investigation are Coratina and Chamlali from Italy and Tunisia,

The VOOs tested by the panelists produced the aromagrams of Figures 8 and 9. According to the panel jury, Coratina olive oils extracted by centrifugation (2P and 3P) were very fruity with a good level of bitterness and astringency. These latter attributes seem to disappear

Chamlali olive oils extracted by a pressure system were found slightly defected while olive oils extracted by centrifugation systems were fruity with same level of bitterness and astringency. All these results matched those obtained by SPME-GC/MS (see paragraph

**Coratina PS Coratina 2P Coratina 3P**

Fig. 8. Sensorial wheels of Italian olive oils of Coratina Cv. extracted by pressure system (PS)

and centrifugation two phase and three phase systems (2P and 3P, respectively).

respectively.

3.3).

when a pressure system is employed.

Fig. 5. Bar chart of volatile compounds analysed by SPME-GC/MS. The Cvs under investigation are Coratina and Chamlali from Italy and Tunisia respectively.

Volatile compounds are distributed in a very different concentration in Italian and Tunisian olive oil samples. The flavour of Coratina VOOs was stronger than Chamlali VOOs. In particular, statistical evaluation showed that hexenal (Fig. 6), 1-hexanol (Fig. 7), produced by the lipoxygenase pathway, could discriminate the two VOOs.

Fig. 6. Biplot of hexenal at 99% confidence level. The genotype was the main factor considered. The Cvs under investigation are Coratina and Chamlali from Italy and Tunisia respectively.

Others

Volatile compounds are distributed in a very different concentration in Italian and Tunisian olive oil samples. The flavour of Coratina VOOs was stronger than Chamlali VOOs. In particular, statistical evaluation showed that hexenal (Fig. 6), 1-hexanol (Fig. 7), produced by

Fig. 5. Bar chart of volatile compounds analysed by SPME-GC/MS. The Cvs under investigation are Coratina and Chamlali from Italy and Tunisia respectively.

Fig. 6. Biplot of hexenal at 99% confidence level. The genotype was the main factor

considered. The Cvs under investigation are Coratina and Chamlali from Italy and Tunisia

Extra virgin Italian olive oil

Tunisian olive oil

0.000 1.000 2.000 3.000 4.000

respectively.

Alcohols C6

Alcoholis C5

the lipoxygenase pathway, could discriminate the two VOOs.

Aldehydes C6

Fig. 7. Biplot of 1.hexanol at 95% confidence level. The genotype was the main factor considered. The Cvs under investigation are Coratina and Chamlali from Italy and Tunisia, respectively.

The VOOs tested by the panelists produced the aromagrams of Figures 8 and 9. According to the panel jury, Coratina olive oils extracted by centrifugation (2P and 3P) were very fruity with a good level of bitterness and astringency. These latter attributes seem to disappear when a pressure system is employed.

Chamlali olive oils extracted by a pressure system were found slightly defected while olive oils extracted by centrifugation systems were fruity with same level of bitterness and astringency. All these results matched those obtained by SPME-GC/MS (see paragraph 3.3).

Fig. 8. Sensorial wheels of Italian olive oils of Coratina Cv. extracted by pressure system (PS) and centrifugation two phase and three phase systems (2P and 3P, respectively).

Volatile and Non-Volatile Compounds of Single Cultivar Virgin Olive Oils Produced

in Italy and Tunisia with Regard to Different Extraction Systems and Storage Conditions 13

Fig. 11. Bar chart of free acidity of Chamlali VOOs during a period of experimentation of six months and depending on the type of packaging utilized. The letters stand for: O opaque glass bottle, T transparent glass bottle, PET polyethylene terephtalate bottle and the extraction system employed: SP pressure system, 2P and 3P centrifugation system at two

Chamlali VOOs were the samples that showed the higher indices of deterioration all over the period. The extraction system plays a key role on the value of the free acidity of an oil. In fact, oils extracted by pressure system have higher free acidity values which increase within

Fig. 12. 3D bar chart of free acidity of Coratina and Chamlali VOOs during a period of experimentation of six months and depending on the type of packaging utilized. The letters stand for: O opaque glass bottle, T transparent glass bottle, PET polyethylene terephtalate bottle and the extraction system employed: SP pressure system, 2P and 3P centrifugation

and three phases respectively.

system at two and three phases respectively.

the first month (Fig. 12).

Fig. 9. Sensorial wheels of Tunisian olive oils of Chamlali Cv. extracted by pressure system (PS) and centrifugation two phase and three phase systems (2P and 3P, respectively).

Finally, the organoleptic analysis conducted on custemers demonstrated that consumers prefer olive oils extracted by centrifugation systems rather than olive oils obtained by pressure systems.

#### **3.4 Olive oil storage**

Soon after extraction, samples of the sixty Italian and sixty Tunisian VOOs were divided into three groups of twenty and stored in opaque glass, transparent glass and polyethylene terephtalate (PET) bottles. The storage of the oils in opaque glass bottles seemed to be better as it reduced oxidative changes and prolonged shelf life, while polyethylene terephtalate (PET) bottles were the package system that inhibits deterioration to a lesser extent. In fact, free acidity, over the period of six months, became higher when the oils were stored in PET bottles (Fig. 10 and Fig. 11).

Fig. 10. Bar chart of free acidity of Coratina VOOs during a period of experimentation of six months and depending on the type of packaging utilized. The letters stand for: O opaque glass bottle, T transparent glass bottle, PET polyethylene terephtalate bottle and the extraction system employed: SP pressure system, 2P and 3P centrifugation system at two and three phases respectively.

**Chamlali PS Chamlali 2P Chamlali 3P**

Fig. 9. Sensorial wheels of Tunisian olive oils of Chamlali Cv. extracted by pressure system (PS) and centrifugation two phase and three phase systems (2P and 3P, respectively).

Finally, the organoleptic analysis conducted on custemers demonstrated that consumers prefer olive oils extracted by centrifugation systems rather than olive oils obtained by

Soon after extraction, samples of the sixty Italian and sixty Tunisian VOOs were divided into three groups of twenty and stored in opaque glass, transparent glass and polyethylene terephtalate (PET) bottles. The storage of the oils in opaque glass bottles seemed to be better as it reduced oxidative changes and prolonged shelf life, while polyethylene terephtalate (PET) bottles were the package system that inhibits deterioration to a lesser extent. In fact, free acidity, over the period of six months, became higher when the oils were stored in PET

Fig. 10. Bar chart of free acidity of Coratina VOOs during a period of experimentation of six months and depending on the type of packaging utilized. The letters stand for: O opaque glass bottle, T transparent glass bottle, PET polyethylene terephtalate bottle and the extraction system employed: SP pressure system, 2P and 3P centrifugation system at two

pressure systems.

**3.4 Olive oil storage** 

bottles (Fig. 10 and Fig. 11).

and three phases respectively.

Fig. 11. Bar chart of free acidity of Chamlali VOOs during a period of experimentation of six months and depending on the type of packaging utilized. The letters stand for: O opaque glass bottle, T transparent glass bottle, PET polyethylene terephtalate bottle and the extraction system employed: SP pressure system, 2P and 3P centrifugation system at two and three phases respectively.

Chamlali VOOs were the samples that showed the higher indices of deterioration all over the period. The extraction system plays a key role on the value of the free acidity of an oil. In fact, oils extracted by pressure system have higher free acidity values which increase within the first month (Fig. 12).

Fig. 12. 3D bar chart of free acidity of Coratina and Chamlali VOOs during a period of experimentation of six months and depending on the type of packaging utilized. The letters stand for: O opaque glass bottle, T transparent glass bottle, PET polyethylene terephtalate bottle and the extraction system employed: SP pressure system, 2P and 3P centrifugation system at two and three phases respectively.

Volatile and Non-Volatile Compounds of Single Cultivar Virgin Olive Oils Produced

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