Denis Rusjan,* Zora Koroec-Koruza
Ljubljana, Biotechnical Faculty, Jamnikarjeva 101, SI-1001 Ljubljana, Slovenia.
Paper based on a
presentation at the 12th International Symposium on Separation
Sciences, Lipica, Slovenia,
September 2729, 2006.
The content of phenolic compounds in grape skins of the red grape variety Merlot using different extraction solvents and analytical techniques were studied. The 1% solution of 2,6-di-tert-butyl-4-methylphenol (BHT) in methanol and ethanol/ formic acid/water solution were used as extraction media, and the content of phenolic compounds was determined using HPLC and spectrophotometry. Methanol compared to ethanol/formic acid/water performed better, as statistically significantly higher contents were determined.
The following contents were determined: (+)-catechin 6874 mg kg1, (-)-epicatechin 3235 mg kg1, oenin 440450 mg kg1, rutin 2.93.5 mg kg1, myricetin 0.40.5 mg kg1, kaempferol 2.3 mg kg1 and quercetin 3.23.6 mg kg1. Using spectrophotometry, an arbitrary procedure was followed for determination of phenolic compounds extracted with ethanol/formic acid/water. Thus, the content of total phenols (7911127 mg kg1), tartaric esters (219 mg kg1), flavonols (163167 mg kg1) and total anthocyanins (21792219 mg kg1) was determined. A comparison with literature data is difficult due to different varieties studied, ecological conditions, ripening stage, analytical methods etc., but some similarities can be observed. For our understanding of the process of grape maturation and its quality, it is of importance to develop a reliable and simple method.
Keywords: grape analysis, wine, extraction, antioxidants, chromatography, spectrophotometry