COOH
5. Conclusions
Occurrence and Analysis of Phenolic Compounds 85
For the quantification of flavanones and dihydroflavonols, the spectrophotometric method based on the interaction of these compounds with 2,4-dinitrophenylhydrazine in acidic media (sul-furic acid) to form colored phenylhydrazones has been reported (109). The absorbance was measured at 486 nm.
Quantification of anthocyanins takes advantage of their char-acteristic behavior in acidic media. The analytical procedure for quantification of anthocyanins was first developed by Sondheimer and Kertesz (110) and modified by Swain and Hillis (111) who suggested expressing the concentration of pigments in terms of the change in the absorbance at λmax between pH 3.5 and pH≤ 1.0.
Finally, Schulz et al. (112) used a near-infrared reflectance spectroscopic method for prediction of polyphenols in the leaves of green tea (Camelia sinensis L) while Edelmann et al. (113) developed a rapid method of discrimination of Austrian red wines based on mid-infrared spectroscopy of phenolic extracts of wine.
86 Stalikas
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