3 research outputs found
Assessing the Impact of Smoke Exposure in Grapes: Development and Validation of a HPLC-MS/MS Method for the Quantitative Analysis of Smoke-Derived Phenolic Glycosides in Grapes and Wine
Bushfires occur frequently in the vicinity of grape growing
regions,
resulting in smoke drifting over the vineyards. Wine made from smoked
grapes is often downgraded or unfit for sale due to negative sensory
characters. To manage or avoid the risk of producing smoke-affected
wine, a diagnostic assay was developed for assessing the extent of
smoke exposure in grapes and the resulting wines. The method relies
on the quantitation of the glycosidic grape metabolites that are formed
from major volatile phenols present in smoke. Using HPLC-MS/MS with
APCI, a quantitation method for phenolic glycosides as smoke marker
compounds was developed and validated. The method was confirmed to
be of sufficient sensitivity and reliability to use as a diagnostic
assay. On the basis of phenolic glycoside concentrations, grapes or
wine can be assessed as smoke exposed or not, and the relative intensity
of smoke exposure can be determined
Determination of the Importance of In-Mouth Release of Volatile Phenol Glycoconjugates to the Flavor of Smoke-Tainted Wines
The
volatile phenols guaiacol, 4-methylguaiacol, syringol, 4-methylsyringol, <i>o</i>-, <i>m</i>-, and <i>p-</i>cresol,
as well as their glycoconjugates, have previously been shown to be
present in elevated concentrations in smoke-tainted wine. Sensory
descriptive analysis experiments, with addition of free volatile phenols
in combination with their glycosidically bound forms, were used to
mimic smoke taint in red wines. The addition of volatile phenols together
with glycoconjugates gave the strongest off-flavor. The hydrolysis
of glycosidically bound flavor compounds in-mouth was further investigated
by in vitro and in vivo experiments. The results indicate that enzymes
present in human saliva are able to release the volatile aglycones
from their glycoconjugates even under low pH and elevated ethanol
conditions, confirming that in-mouth breakdown of monosaccharide and
disaccharide glycosides is an important mechanism for smoke flavor
from smoke affected wines, and that this mechanism may play an important
general role in the flavor and aftertaste of wine
Contribution of Several Volatile Phenols and Their Glycoconjugates to Smoke-Related Sensory Properties of Red Wine
Guaiacol and 4-methylguaiacol are well-known as contributors
to
the flavor of wines made from smoke-affected grapes, but there are
other volatile phenols commonly found in smoke from forest fires that
are also potentially important. The relationships between the concentration
of a range of volatile phenols and their glycoconjugates with the
sensory characteristics of wines and model wines were investigated.
Modeling of the attribute ratings from a sensory descriptive analysis
of smoke-affected wines with their chemical composition indicated
the concentrations of guaiacol, <i>o</i>-cresol, <i>m</i>-cresol, and <i>p</i>-cresol were related to
smoky attributes. The best-estimate odor thresholds of these compounds
were determined in red wine, together with the flavor threshold of
guaiacol. Guaiacol β-d-glucoside and <i>m</i>-cresol β-d-glucoside in model wine were found to
give rise to a <i>smoky/ashy</i> flavor in-mouth, and the
respective free volatiles were released. The study indicated that
a combination of volatile phenols and their glycosides produces an
undesirable smoke flavor in affected wines. The observation of flavor
generation from nonvolatile glycoconjugates in-mouth has potentially
important implications