Ethyl and Vinyl Phenols in Wines

In addition, SPME methods of direct on-fiber derivatization with PFBOA (Vesely et al.,2003 Carlton et al.,2007) and direct derivatization on an SPE cartridge using a styrene-vinylbenzene polymer stationary phase (Ferreira et al., 2004 Cullere et al., 2004), were proposed. Derivatization at 50 °C on a PEG-DVB fiber previously adsorbed on PFBOA showed very low reaction yield for acetoin and diacetyl, probably due to high polarity, and consequently the low volatility, of these compounds (Table 5.11A) (Flamini et al., 2005b). 

Volatile phenols originate from hydroxycinnamic acids (ferulic, p-coumaric, or caffeic acid) by the action of hydroxycinnamate decarboxylase enzyme, which turn the hydroxycinnamics acid into vinylphe-nols (Albagnac, 1975 Grando et al., 1993). Then, these compounds are reduced to ethyl derivatives by vinylphenol reductase enzymes characteristic of species, such as Dekkera bruxellensis, Dekkera anomala, Pichia guillermondii, Candida versatilis, Candida halophila, and Candida mannitofaciens (Edlin et al., 1995 1998 Dias et al., 2003 Chatonnet et al., 1992 1995 1997 Dias et al., 2003), apart from very small quantities produced by some yeasts and lactic acid bacteria under peculiar growth conditions (Chatonnet et al., 1995 Barata et al., 2006  

Volatile phenols greatly influence the aroma of wine, the most important are 4-vinylphenol (4-VP), 4-vinylguaiacol (4-VG), 4-ethylphenol (4-EP), and 4-ethylguaiacol (4-EG) (Chatonnet et al., 

The 4-EP compound was reported in wine for the first time in 1967 by Webb and co-workers and its presence, together with the other phenols cited, was confirmed in 1970 by Dubois and Brule (Webb, 1967 Dubois and Brule, 1970). 

Oligomer proanthocyanidins inhibit Saccharomyces cerevisiae cin-namate decarboxylase (Chatonnet et al., 1990), justifying the very low amounts of vinylphenols in red wines on the contrary, Brettanomyces decarboxylase is not inhibited by proanthocyanidines (Chatonnet et al., 

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