1. Color Variation in standard Virgin-Olive-Oil Tasting Glasses
Universidad de Granada
Universidad de Sevilla
Instituto de la Grasa
1/18
Color Variation in standard
Virgin-Olive-Oil Tasting Glasses
Good Afternoon, I am Luis Gómez Robledo and this is the work that I’m going to expose: “Color Variation in standard Virgin Olive Oil Tasting Glasses”. It has been a work between the Basic and Applied Colorimetry Lab form the University of Granada, the Bromatology lab from the University of Sevilla and the Fat Institute of Sevillia.
L. Gómez-Robledoa, M. Melgosaa, F.J. Herediab, M.J. Moyanoc, R. Roaa, R. Huertasa
a Basic and App. Colorimetry Lab.Departamento de Óptica, Facultad de Ciencias, Universidad de Granada, Spain,
b Laboratorio de Bromatología , Facultad de Farmacia, Universidad de Sevilla,, Spain
c Almazara Experimental del Instituto de la Grasa, CSIC, Sevilla, Spain

2. 2/18
Introduction
Let’s start with the introduction: The quality control of oils have two parts, the chemical analysis and the sensorial analysis. Both ones have the same importance. Here we are going to talk about the second one, the sensorial analysis.

3. Quality Control of Oils
Introduction
3/18
Quality Control of Oils
Chemical Analysis
Sensorial Analysis
This sensorial analysis, tasting, is made in cabins as we see in this figure, it is a white cabin with a good ilumination and free of smells and noises to keep all the taster senses putted into the oil. The taste is made in glasses with the geometry that we see in this figure, it follows some rules of the international olive oil council:
J. Alba et al. Aceite de oliva virgen. Análisis Sensorial, 1997

4. Introduction
3/18
This sensorial analysis, tasting, is made in cabins as we see in this figure, it is a white cabin with a good ilumination and free of smells and noises to keep all the taster senses putted into the oil. The taste is made in glasses with the geometry that we see in this figure, it follows some rules of the international olive oil council:
J. Alba et al. Aceite de oliva virgen. Análisis Sensorial, 1997

5. Standard COI/T.20/Doc.nº 5/18 June 1987
Introduction
3/18
Standard COI/T.20/Doc.nº 5/18 June 1987
It describes the features of glasses that are used in Olive Oil tasting.
Stability to avoid spillage.
The bottom of the glass must be prepared to homogenize the temperature of the oil.
The geometry of the glass must preserve the bouquet of the oil.
The glass must be dark to block the color of the oil.
It describes the features of glasses that are used in Olive Oil tasting.
Stability to avoid spillage
The bottom of the glass must be prepared to homogenize the temperature of the oil.
The geometry of the glass must preserve the bouquet of the oil.
The glass must be dark to block the color of the oil .... because it can confuse the sense of the taster
Agustí Romero, Joan Tous. Percepnet. 2005

6. Introduction
4/18
….these glasses are blue and transparent, and our experience says us that we can see when is something inside them, so…

7. Introduction
4/18
Objective
To check if the tasting glasses that are used in the official tasting (COI/T.20 rule) are able to avoid the taster to distinguish the color of the extra virgin olive oils.
the objective of this work is: “To check if the tasting glasses that are used in the official tasting are able to avoid the taster to distinguish the color of the extra virgin olive oils”. To achieve this objective we make three questions:…

8. Introduction
4/18
Objective
To check if the tasting glasses that are used in the official tasting (COI/T.20 rule) are able to avoid the taster to distinguish the color of the extra virgin olive oils.
Does the color of one oil change when we change the glass?
Is very different the color of two oils in the same glass?
Is very different the color of different oils in different glasses?
Does the color of one oil change when we change the glass?
Are very different two oils in the same glass?
Are very different different oils in different glasses?

9. 5/18
Material and method
To answer these questions we have done the following method

10. 18 standard tasting glasses
Material and method
6/18
18 standard tasting glasses
*Values out of the rule
Number of the glass
Capacity
(ml)
Height
(mm)
Rim’s diameter (mm)
Greater diameter (mm)
Diameter at bottom (mm)
Thickness of glass at bottom(mm)
Thickness of the glass at side (mm) 1
128,00
61,00
*45,82
*68,24
*40,00
*6,70
*2,68 2
136,00
*61,18
50,00
71,06
*24,00
*6,24
*2,60 3
*142,00
*63,54
51,00
*68,74
*25,14
*6,54
1,66 4
*59,82
50,28
70,88
*25,06
*6,12
*2,86 5
140,00
*61,20
*45,90
*68,76
*40,58
5,40
*1,90 6
*144,00
60,50
*46,10
69,20
34,00
*4,38
1,70 7
*160,00
60,40
49,28
71,10
*21,68
*3,82
*2,40 8
*61,82
*45,20
*68,84
*31,58
*6,22
*2,00 9
138,00
59,72
49,60
70,40
*27,66
5,72
*2,62 10
59,74
49,82
*71,08
*26,70
*7,36
*2,66 11
*148,00
59,44
49,74
70,92 12
*156,00
*61,08
49,40
70,74
*28,22
*7,38 13
49,96
*71,16
*26,48
*2,22 14
*150,00
60,38
*48,04
*71,04
*28,00
*6,30 15
*154,00
59,32
49,42
70,50
*30,78
4,70
*1,18 16
60,10
49,68
70,90
*25,80
*7,16
*2,78 17
132,00
60,98
*43,10
*23,25
*8,58 18
*63,14
*47,10
*30,20
*7,84
*2,14
Mean
144,33
60,77
48,30
70,28
28,71
6,35
2,32
Standard deviation
8,44
1,16
2,21
1,01
5,20
1,23
0,47
We took eighteen glasses fom different laboratories and mills these glasses are used for official tasting. As we can see in the tabe their size can differ more or less from the standard glass proposed of the International olive oil council. For example, the mean thickness of the glass differ in about 1mm of the standard proposed glass.
Standard glass
130±10
60±1
50±1
70±1
35±1
5±1
1,5±0,2

11. Spectralight III Cabinet Light source simulator D65
Material and method
7/18
SpectraScan PR-704
GretagMacbeth
Spectralight III Cabinet
Light source simulator D65
3 measures of each glass
The color measureof the glasses without oil was made as we see in this figure, everything was made with white background and ground measured with a spectrophotometer spectrascan Pi er seven hundred and four in a GretagMacbeth Cabin with a D65 source light, in all color computation we have used the estándar observer CIE sixtyfour

12. Spectrum of the 18 glasses
Material and method
8/18
Spectrum of the 18 glasses
The obtainted transmittances for the eighteen glasses are in this figure. The spectrum is not only blue there is also transmitance in the red region.
We were too surprised, because the transmittances are very different

13. Color of the 18 glasses assuming: D65 Illuminant
Material and method
9/18
Color of the 18 glasses assuming:
D65 Illuminant
CIE64 Standard Observer
And here we have the CIELAB coordinates of the eighteen glasses, we can see glasses with very dark color and glasess very light.
We can note here that the croma keeps constant and the hue angle changes a lot.

14. 10 Spanish commercial extra-virgin olive oils.
Material and method
10/18
10 Spanish commercial extra-virgin olive oils.
Sample
L*ab,10
a*10
b*10 1
76,97
14,35
117,44 2
74,85
15,66
112,97 3
78,87
17,30
120,56 4
64,26
13,18
100,93 5
69,28
11,42
106,00 6
71,52
10,90
107,93 7
68,87
12,04
105,68 8
70,45
12,27
107,58 9
62,62
12,56
95,53 10
69,31
11,21
105,32
To check the glasses we have choosen ten different Spanish comercial extra-virgin olive oils with a good variety of colors

15. 18 Standard tasting glasses. 10 Spanish extra-virgin olive oils.
Material and method
11/18
18 Standard tasting glasses.
10 Spanish extra-virgin olive oils.
3 different geometries.
Total: 540 measures.
We measured each oil in each glass and to simulate different posibilites in wich a taster could see we measured at three different angles, zero degrees, thirty degrees and sixty degrees. At zero degrees the line vision cross twice the glass and have the white background behind.
When light comes from It is behind the oil. It makes a total of 540 measures.

16. 12/18
Results
All this measures give us some results…

17. Does the color of one oil change when we change the glass?
Results
13/18
Does the color of one oil change when we change the glass?
To answer the first question: “Does the color of one oil change when we change the glass?” Whe variated the glass and fixed each oil…

18. Does the color of one oil change when we change the glass?
Results
13/18
Does the color of one oil change when we change the glass?
Whe have computed the average CIELAB coordinates for each oil in the eighteen glasess

19. Does the color of one oil change when we change the glass?
Results
13/18
Does the color of one oil change when we change the glass?
And we have obtained the color difference CIELAB between each point and the mean

20. Does the color of one oil change when we change the glass?
Results
13/18
Does the color of one oil change when we change the glass?
Te meaan value of this color difference is a measure of dispersion, it is called…

21. Does the color of one oil change when we change the glass?
Results
13/18
Does the color of one oil change when we change the glass?
Te meaan value of this color difference is a measure of dispersion, it is called…
Mean
Color
Difference
respect to the
R. Berns

22. Color diferencies in CIELAB units
Resultados
13/18
Does the color of one oil change when we change the glass?
Color diferencies in CIELAB units
Oil 0°
30°
60°
MCDM SD 1
1,96
1,60
3,72
2,51
4,80
3,36 2
1,83
1,56
3,07
2,23
4,25
3,15 3
2,12
2,73
3,05
2,04
3,70
2,49 4
1,18
1,07
3,25
3,93
3,29 5
2,03
1,86
3,50
1,87
4,35
3,85 6
1,73
1,84
3,44
4,67
3,79 7
2,67
3,09
3,12
2,75
2,86 8
2,08
2,10
3,90
2,19
4,27
2,81 9
1,38
1,09
3,78
2,26
5,15
3,18 10
2,28
4,07
1,92
4,41
2,84
Mean/SD
1,93
0,43
3,49
0,37
4,30
0,51
the values for this MCDM for each oil and each geometry is in this table, we can see that the MCDM and the standard deviation do not change too much when we change the oil, there is important differences if we change the geometry, the color of the different glasses change considerably
*L. Gómez-Robledo et al. JAOCS in press
MCDM of oils in a 46,4 mm transparent Pyrex Glass*= 6,9 CIELAB units

23. Is very different the color of two oils in the same glass?
Results
14/18
Is very different the color of two oils in the same glass?
To ask the second question ¿Are very different two oils in the same glass? We have realized the same calculation of theMCDM

24. Is very different the color of two oils in the same glass?
Results
14/18
Is very different the color of two oils in the same glass? 0°
30°
60°
Glass
MCDM SD 1
0,39
0,18
1,17
0,79
2,27
1,73 2
1,41
0,89
1,78
0,94
3,36
1,82 3
1,03
0,53
1,36
0,71
3,02
1,18 4
1,02
0,73
2,28
1,28
2,95
2,42 5
0,42
1,97
1,08
1,86
1,21 6
1,15
0,70
1,85
0,77
1,74
1,31 7
3,66
4,56
3,00
1,92
6,66
1,50 8
0,66
0,43
1,19
0,90
2,62
1,61 9
1,48
1,01
0,84
2,56
1,47 10
1,34
0,87
1,26
0,93
2,26 11
1,23
0,91
2,29
1,42 12
1,25
0,85
2,93
1,93 13
1,37
0,76
0,61
2,71 14
0,82
0,46
2,40
1,51 15
3,79
1,63
1,84
0,83
3,01 16
1,16 17
1,04
0,49
2,01 18
0,54
1,53
1,91
Mean/SD
1,38
1,71
2,76
Mean
Color
Differences
respect to the
Now we have fixed the glass and we have obtained the MCDM changing the oil. Here we see that the color of the glass does not chanche too much. The MCDM increases when we increase de angle, but this is normal, at sixty degrees the light only crosses one side of the glass.
*L. Gómez-Robledo et al. JAOCS in press
MCDM of oils in Pyrex Glass= 6,9 CIELAB units

25. Is very different the color of different oils in different glasses?
Results
15/18
Is very different the color of different oils in different glasses?
But in a real tasting, we have different oils in different glasses, we can ask us if it is perceptible the color difference between these different oils in different glasses…

26. Is very different the color of different oils in different glasses?
Results
15/18
Is very different the color of different oils in different glasses?
We have one hundred and fifty three different pairs of glasses…

27. Is very different the color of different oils in different glasses?
Results
15/18
Is very different the color of different oils in different glasses?
and one fourty five pairs of oils,
But, here, the position of the oil is important, in example: the oil 1 can be in glass A and the oil 2 in glass B, and this will have different color if we put the oil 1 in glass B and the oil 2 in glass A

28. Is very different the color of different oils in different glasses?
Results
15/18
Is very different the color of different oils in different glasses?
So we have thirteen thounsand seven hundred and seventy pairs of different oils in different glasses. Obtaining thirteen thounsand seven hundred and seventy color differences
for each pair we have this figure
13770 combinations for each geometry

29. Is very different the color of different oils in different glasses?
Results
16/18
Is very different the color of different oils in different glasses?
13770 combinations for each geometry
ΔE ab,10 SD 0°
3,07
2,87
30°
5,25
60°
6,89
4,59
*L. Gómez-Robledo et al.
JAOCS 2008 (in press)
…in wich there are represented the number of pairs with a color difference between zero and two, two and four, etcetera. The mean value of this figure is shown in this table, and we have the same calculation for the 45 pairs of oils measured in a Pyrex glass of a near diameter. The mean color difference obtained it is minor than in coloured glasses.
Mean of measures in a 46,4 mm transparent Pyrex Glass*
10,96
7,23

30. 17/18
Conclusions
Once we have showed these results we can conclude that..

31. Conclusions
18/18
The present tasting glasses obey the International Olive Oil Council rules in an acceptable way. The color differences are perceptible.
Manufactures must follow the dimensions of the standard glasses, adding a fixed color specification with corresponding tolerances.
Improve the sensorial analysis we propose two types: opaque glasses to a taste analysis and transparent glasses to a color sensorial analysis.
the tasting glasses obey the International Oil Council rules (COI) in an acceptable way, although the color differences obtained are remarkable (greater than 1 CIELAB unit) we must take into account that a taster doesn’t compare the color of the oils in the glasses, he tastes the oils one by one..
However, in these results, we can see that it is possible to distinguish two oils (mainly if we use different glasses). If the purpose of the tinted glasses is to hide the oil color then it would be useful to use opaque glasses with internal sides black, so the taster could not appreciate the appearance of the oil.
2-. The present tasting glasses obey the International Olive Oil Council rules in an acceptable way.
1-.Manufactures must follow the dimensions of the standard glasses, adding a fixed color specification with corresponding tolerances.
3-. Copas negras o transparentes

32. Thanks a lot for your attention
Aknowledments:Research Project P06-AGR-01744, Consejería de Innovación, Ciencia y Empresa; Junta de Andalucía (Spain).