Volume 76, Part 3, October 2015, Pages 550–560
Aroma compounds in Ontario Vidal and Riesling icewines. II. Effects of crop level
Highlights
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- Control; fruit set cluster thinned (TFS); veraison-thinned (TV) were assessed for Riesling and Vidal icewine volatiles
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- Vidal volatiles differed with treatment and were highest in: control, TV (2003); TFS (2004)
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- PCA found e.g. β-damascenone, ethyl 2- and 3-methylbutyrate, ethyl isobutyrate related to control
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- Riesling volatiles differed with crop level and most were highest in TV
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- Odor activity values were highest for: e.g. β-damascenone, ethyl octanoate, cis-rose oxide
Abstract
Icewine
is a dessert wine of substantial commercial value to the Canadian wine
industry. Many grapegrowers crop icewine-designated vines at levels
double those for table wines; therefore, the experimental objective was
to ascertain whether reducing crop level might impact icewine chemical
and aroma compound profiles. Three treatments [control (fully-cropped);
cluster thin at fruit set to one (basal) cluster per shoot (TFS);
cluster thin at veraison (TV)] were evaluated in randomized block
experiments for Riesling and Vidal over two seasons (2003–04; 2004–05).
Treatments differed in must pH and titratable acidity (both years) and
although wines differed for most standard chemical variables, no clear
trends existed. Vidal icewines had the highest aroma compound
concentrations in the control and TV (2003) and in TFS (2004). Most
Vidal aroma compounds differed with crop level: 17/24 (2003) and 23/24
(2004). Vidal odor activity values (OAVs) were highest for:
β-damascenone, ethyl octanoate, cis-rose oxide, 1-octen-3-ol, ethyl hexanoate, isoamyl acetate (2003); β-damascenone, 1-octen-3-ol, ethyl octanoate, cis-rose
oxide, and ethyl hexanoate (2004). Principal component analysis (PCA)
found β-damascenone, ethyl 2- and 3-methylbutyrate, ethyl isobutyrate,
ethyl butyrate and 1-heptanol correlated and associated with the control
(2003), but most compounds were positively loaded on PC1 and associated
with replicate, not crop level (2004). All Riesling aroma compounds
differed with crop level (2003) and 22/23 (2004). Both years, most aroma
compounds were highest in TV and lowest in TFS wines. Riesling OAVs
were highest for: β-damascenone, ethyl octanoate, and ethyl hexanoate
(2003, 2004); cis-rose oxide was highly odor potent (2004). PCA
of Riesling showed most compounds loaded on PC1 and associated with TV
wines (2003). Freeze/thaw events in November/December appeared more
important in aroma compound development than adjustment of crop level,
and it is therefore concluded that reduction of crop level in Vidal and
Riesling vines would not substantially impact icewine aroma composition.
Keywords
- Gas chromatography;
- Mass spectrometry;
- Odor-potent compounds;
- Cluster thinning;
- Monoterpenes;
- Norisoprenoids
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