Smoke-derived taint in wine: the release of smoke-derived volatile phenols during fermentation of Merlot juice following grapevine exposure to smoke.
The release of smoke-derived volatile phenols during the fermentation of Merlot grapes, following grapevine exposure to smoke, has been investigated. The concentrations of guaiacol, 4-methylguaiacol, 4-ethylguaiacol, 4-ethylphenol, and eugenol were determined by gas chromatography-mass spectrometry and found to increase throughout the winemaking process. Only trace levels (< or = 1 microg/L) of guaiacol and 4-methylguaiacol could be detected in free run juice derived from the fruit of smoked vines; the highest levels, 388 microg/L and 93 microg/L, respectively, were observed in the finished wine. Control wine (derived from fruit of unsmoked vines) contained 4 microg/L guaiacol, with the volatile phenols either not detected or detected at only trace levels (< or = 1 microg/L) throughout fermentation. The role of enzyme and acid catalyzed hydrolysis reactions in releasing smoke-derived volatile compounds was also investigated. The volatile phenols were released from smoked free run juice by strong acid hydrolysis (pH 1.0) and enzyme (beta-glucosidase) hydrolysis, but not mild acid hydrolysis (juice pH 3.2-3.7). Guaiacol was again the most abundant smoke-derived phenol, present at 431 microg/L and 325 microg/L in strong acid and enzyme hydrolysates, respectively. Only trace levels of each phenol could be detected in each control hydrolysate. This study demonstrates the potential for under-estimation of smoke taint in fruit and juice samples; the implications for the assessment of smoke taint and quantification of volatile phenols are discussed.
Kennison
Kristen R
KR
Department of Agriculture and Food Western Australia, P. O. Box 1231, Bunbury, Western Australia 6230, Australia.
Gibberd
Mark R
MR
Pollnitz
Alan P
AP
Wilkinson
Kerry L
KL
D005054:Eugenol / Q000032:analysis; D005285:Fermentation; D005638:Fruit / Q000737:chemistry / Q000254:growth & development; D006139:Guaiacol / Q000032:analysis; D006868:Hydrolysis; D009812:Odorants / Q000032:analysis*; D010636:Phenols / Q000032:analysis*; D012906:Smoke / Q000032:analysis*; D027843:Vitis / Q000254:growth & development*; D014920:Wine / Q000032:analysis*
D010636:Phenols; D012906:Smoke; D005054:Eugenol; D006139:Guaiacol