3 Methods
3.1
Spectrophotometry
(Transmission
Measurement)
This approach is normally used to measure the absorbance of a
carotenoid extract and/or characterize its colour. Thus, this
approach was used to establish relationships colour-structure in
common dietary carotenoids [7]. Examples of classical spectrophotometric determination of carotenoids are provided elsewhere [4].
1. Centrifuge the samples at 3220 Â g for 10 min at 20
C (see
Note 2).
2. Filter the samples through the filters before the colour
determination.
3. Turn on the spectrophotometer to stabilize it about 30 min
before the measurements.
4. Click on the SPT HP8452 program icon to run the software.
5. Open the method (previously created, see Note 3).
6. Fill the cuvette with an appropriate blank (usually the solvent
the carotenoids are dissolved in) and place it in the cuvette
holder.
7. Click on the icon Blank to perform the measurement of the
blank.
8. Fill the cuvette with the filtered sample and place it in the
cuvette holder (see Notes 4 and 5).
9. Click on the icon Sample to perform the measurement of the
sample.
10. Save the measure: File/Save (Select the place to save the spectra
of the samples)/OK.
11. To obtain the colour parameters, it is necessary to export the
spectra in DX format.
12. Open the sample file and select the spectrum.
13. Export the selected spectrum as DX format.
14. Open the DX files with the CromaLab program to obtain the
colorimetric parameters.
15. From the carotenoid content determined by analytical techniques and the colorimetric parameters measured by spectrophotometry, look for statistical models that allow to estimate the
carotenoid concentration in other samples from the colour
measurements.
3.2
Spectroradiometry
(Reflection
Measurement)
This methodology has been applied to characterize the colour of
citrus and tomato products and, in some cases, to relate it with their
carotenoid levels or even theoretical vitamin A or in vitro antioxidant capacity of carotenoid-containing extracts [33–38].
Applications of Visible Spectroscopy and Color Measurements in the. . .
111
3.1
Spectrophotometry
(Transmission
Measurement)
This approach is normally used to measure the absorbance of a
carotenoid extract and/or characterize its colour. Thus, this
approach was used to establish relationships colour-structure in
common dietary carotenoids [7]. Examples of classical spectrophotometric determination of carotenoids are provided elsewhere [4].
1. Centrifuge the samples at 3220 Â g for 10 min at 20
C (see
Note 2).
2. Filter the samples through the filters before the colour
determination.
3. Turn on the spectrophotometer to stabilize it about 30 min
before the measurements.
4. Click on the SPT HP8452 program icon to run the software.
5. Open the method (previously created, see Note 3).
6. Fill the cuvette with an appropriate blank (usually the solvent
the carotenoids are dissolved in) and place it in the cuvette
holder.
7. Click on the icon Blank to perform the measurement of the
blank.
8. Fill the cuvette with the filtered sample and place it in the
cuvette holder (see Notes 4 and 5).
9. Click on the icon Sample to perform the measurement of the
sample.
10. Save the measure: File/Save (Select the place to save the spectra
of the samples)/OK.
11. To obtain the colour parameters, it is necessary to export the
spectra in DX format.
12. Open the sample file and select the spectrum.
13. Export the selected spectrum as DX format.
14. Open the DX files with the CromaLab program to obtain the
colorimetric parameters.
15. From the carotenoid content determined by analytical techniques and the colorimetric parameters measured by spectrophotometry, look for statistical models that allow to estimate the
carotenoid concentration in other samples from the colour
measurements.
3.2
Spectroradiometry
(Reflection
Measurement)
This methodology has been applied to characterize the colour of
citrus and tomato products and, in some cases, to relate it with their
carotenoid levels or even theoretical vitamin A or in vitro antioxidant capacity of carotenoid-containing extracts [33–38].
Applications of Visible Spectroscopy and Color Measurements in the. . .
111