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Composition of tomatoes and tomato products in antioxidants (WG1) page 95
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Phenolics can be detected under UV wavelengths, 280 nm for flavanone glycosides
and 313 nm for the polymethoxylated flavones. Fluorescence detection is an obvious mean of
improving sensitivity and selectivity in flavonoid analysis. Electrochemical detection of
phenolics has been described. Eluted species were characterized by retention data and
voltammetric responses.
10. Conclusions about analysis data
Many methods were described to measure lycopene, polyphenols and vitamin C in tomatoes.
For lycopene, the measurement of red colour by a chromatometer is quite related to the
lycopene content, however this method is not sensible enough and cannot determine all
carotenoids.
Determination of lycopene at 502 nm using a spectrophotometer is more specific than the first
one but less than high performance liquid chromatography (HPLC). Numerous HPLC
analysis were described including normal, reverse and supercritical phase. Reverse phase
methods appear more reproducible and more adequate for routine analysis.
Total polyphenols can be determined by the classical method of Folin but HPLC methods are
again more specific.
Total vitamin C can be measured by a colorimetric method but both ascorbic and
dehydroascorbic acids can be measured by HPLC.