Can vineyard cover crop
management change grape
aroma composition
Michael C. Qian
Department of Food Science and Technology
Oregon State University
Email: michael.qian@oregonstate.edu
Student: Hui Feng
Collaborator: Patty Skinkis
Outline
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Introduction to wine flavor chemistry
Objectives for vineyard cover crop project
Free volatile analysis in grapes
Flavor potential analysis in grapes
Wine flavor evaluation
Wine Aroma
• Aroma is one of the most important attributes for
wine quality
• Volatile compounds in concentrations exceeding
their sensory thresholds contribute to aroma
(odor-active).
• Hundreds to thousands volatile compounds can
contribute to wine aroma
• Variations in concentration responsible for the
bouquet of a specific wine
• Volatility of the compounds, interaction with
matrix all affect flavor perceiption
Origin of Wine Aroma
Fermentation aroma (Secondary aromas),
generated primarily during the fermentation.
They are qualitatively and quantitatively the
largest amount of volatile compounds
present in the wine.
Ethanol, C3-C5 straight chain and branched
chain alcohols, 2-phenylethanol
Ethyl esters, acetates (isoamyl acetate)
Fatty acids
Diacetyl (from malolactic fermentation)
Origin of Wine Aroma
Aging aroma, tertiary aromas, generated during
maturation or aging processes. They are
subsequent to vinification.
Oak Lactone: Oak’s Typical Aroma
• Highly aromatic lactone:
– β-methyl-γ-octalactone
– 2 isomers
– aroma threshold of cis and trans racemic
forms
• cis form is 0.001 mg/L
• trans form 0.02 mg/L
• During natural drying there is a net increase
due to breakdown of precursors (lipidic
esters).
• Trans is more stable
• cis- precursor is largely hydrolyzed
during seasoning.
Simple Phenols:
• Thermal degradation of phenolic aldehydes
produces volatile phenols:
– Guaiacol (smoky)
– 4-Methyl-guaiacol (smoky)
– Eugenol (spicy,cloves)
• American Oak
– High in eugenol
Furanic Aldehydes
• Carbohydrate degradation produces furanic
aldehydes:
• 5-Methyl-furanal (caramel)
• Furfuryl alcohol
• 2-Acetyl-furan (slightly burnt, sweet)
• 2,5-Diformyl furan
• Maltol (caramel)
• Furaneol, (pineapple, strawberry, lichi)
• Hydroxymaltol (Jam or burnt sugar)
Origin of Wine Aroma
Grape aroma, primary aromas, present in
the grapes and persisting through
vinification. They characterize a wine.
linalool
geraniol
nerol
TDN
IBMP
cis-rose oxide
wine lactone
2-AAP
3-mercaptopentan-2-one
4-methyl-4-mercaptopentan-2-one
rotundone
Chem. Soc. Rev.,2008,37,2478-2489
Impact odorant contributing to
varietal aroma of selected wines
Chem. Soc. Rev.,2008,37,2478-2489
Pinot noir Wine Aroma
• Pinot noir wine is known to exhibit distinct red fruit
aromas evoking particularly the odors of smallstone fruits (plum and cherry), and of strawberry,
raspberry, black currant, and blackberry.
Volatiles in Burgundy Pinot noir
• Identify and quantify more than 60 volatile compounds
– Alcohols
• isobutanol, 2(3)-me-butanol, 2-phenylethanol, aterpineol, linalool etc.
– Aldehydes and ketones
• 2-hexanone, 2-heptanone, damascenone etc.
– Esters: many
– Hydrocarbons
– Miscellaneous
• No information about aroma compounds
P. Schreier et al, 1980
Aroma in Pinot Noir using GC/Osme
technique
• 3-Methylbutanol
• 2-Phenylethyl acetate
• γ-Nonalactone
propanol
• Ethyl butanoate
2-Phenylethanol
Hexanoic acid
3-(Methylthio)-1Ethyl hexanoate
Miranda-Lopez, Libbey, Watson, McDaniel, 1992
Important odorants in Pinot Noir wines of
Burgundy
O
O
O
Cherry
plum
cinnamic
sweet
O
Fruity, balsamic
Ethyl 2,3-dihydrocinnamate
O
O
Ethyl cinnamate
O
NH2
Fruity, grape
Methyl anthranilate
O
NH2
Sweet,fruity
Ethyl anthranilate
Moio and Etievant, 1995
Aroma Compounds in Oregon Pinot
noir Wine Determined by Aroma
Extract Dilution Analysis (AEDA)
Fang and Qian, Flavor and Fragrance Journal, 2005,20(1): 22-29
Fermentation Related Aroma Compounds
Acids:
2-methylpropanoic acid (rancid)
butanoic acid (cheesy, sweaty),
2-methylbutanoic acid (sweaty)
Alcohols:
2-phenylethanol (rosy),
benzyl alcohol (floral),
3-methyl-1-butanol (nail polish)
Esters:
ethyl fatty acid esters (fresh fruity)
acetates (fruity)
…
Grape Derived Aroma Compounds
• Monoterpenes
Geraniol (floral, rosy)
Linalool (sweet, floral)
α-Terpineol (floral)
• C13-norisoprenoids
β-Damascenone
(sweet apple, honey, floral)
• C6 alcohols
trans-3-Hexenol (green, grass)
cis-3-Hexenol (green, fruity)
1-Hexanol (green)
• Lactones
γ-Nonalactone (coconut)
…
Pinot noir aroma comes from a
combination of numerous aroma
compounds, at the right balance
no single compound can be used for
quantify wine quality
Factors affecting Wine Aroma
• Grape variety
• Grape growing condition:
location
temperature
nitrogen supplement
irrigation, etc.
• Grape harvest quality
• Yeast strains
• Fermentation condition:
temperature
skin contact time, etc.
• Aging condition:
oak type
aging time, etc.
Cover Crops in Vineyard
• Prevent soil erosion in
winter
• Manage soil water and
nutrients in spring
• Control canopy size,
reduce disease pressure
Can Cover Crop Management
Change Grape and Wine Quality?
Experimental design:
Solid cover
Alternative cover
Clean
Analysis of the free and bound volatile compounds
Ground the grapes under liquid nitrogen
Extracted with phosphate buffer
centrifuged and filtered to remove pulp
Free form analysis
Bound form separation
Enzyme hydrolysis
Bound form analysis
Free Volatile Analysis by SBSE-GC-MS
Aroma Precursor Analysis
Filtered Juice
Pass through C18 SPE column
Washed with H2O, CH2Cl2
Eluted with CH3OH
Aroma precursor
Enzyme,0.2 M Citrate, pH3.2, 45°C/24h
Green aroma compound in grapes
• Methoxypyrazines
– IBMP
– Low in Pinot noir grapes
• C6 aldehydes and alcohols
– Linoleic & linolenic acids – main precursors
– Lipoxygenase – enzyme
– Producing a variety of C6 & C9 volatiles compounds such
hexanal, t-2-hexenal, cis-3-hexenol
– Responsible for the “green, grassy” odor
C6 compounds Decrease Sharply at Maturity
H3C
OH
C6 compounds could be used as markers for grape maturity
Effect of cover crop management on free form hexanal and t2-hexenal from 2007 to 2010
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Clean treatment showed the highest concentration of free hexanal and t-2-hexenal.
Solid treatment showed the lowest concentration of free hexanal.
2009, 2010 vintages showed the similar trend
Suggesting that the fruits could be less ripen
May be due to higher vegetative vigor.
Effect of cover crop management on free and bound1-hexanol
from 2007 to 2010
Free 1-hexanol
Bound 1-hexanol
Most Important Terpene Alcohols
50 ppb
400 ppb
18 ppb
130 ppb
400 ppb
130 ppb
Effect of cover crop management on free
linalool
• Solid treatment showed the highest concentration of free linalool.
• Clean treatment showed the lowest concentration of free linalool.
• 2008, 2009 vintage showed the similar trend, no difference shown in2010
Lower glycosidically bound terpene alcohols
for solid cover in general
Effect of cover crop management on bound terpene alcohols
No difference
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Solid treatment show the lowest concentration of bound form a-terpineol.
2008, 2009 and 2010 vintage showed the similar trend.
Terpene Alcohols in Grapes and Wines
Handbook of Enology Volume 2, P. Ribereau-Gayon
Cover crops on C13-norisoprenoidsβ-ionone (μg/kg))
• β-Ionone has an aroma of
raspberry and violets.
• It has a very low perception
threshold of 0.09 µg/L in
synthetic wine
Cover crops on C13-norisoprenoidsβ-damascenone (μg/kg)
• Intense fruity odor with
plum, berry, sugary and rose
nuances
• Sensory threshold 50 ng/L in
wine
• Enhance fruity notes
• Mask the herbaceous aroma
of IBMP
Solid Cover Crop Management
Lowered Bound C13-norisoprenoids
Concentration of aroma compounds in wine from
grape with different cover crop management in 2010
vintage (mean ± SD, ppb)
Compounds
Clean
Alternate
cover
linalool
2.43±0.10a
2.87±0.16a
2.89±0.54a
citronellol
16.86±0.47a
17.83±1.07a
16.70±0.73a
geraniol
2.75±0.21a
2.85±0.19a
2.71± 0.15a
betadamascenone
1.82±0.26ab
2.16±0.42a
1.46±0.07b
beta-ionone
0.38±0.10a
0.37±0.06a
0.27±0.01a
Solid Cover
Conclusion
• Grape and wine quality can be manipulated
through vineyard cover crop management
• Each vineyard is unique
• Cover crop management will depend on many
factors such as soil type, slope, vine density,
water availability, soil nutrients
• Much more research is
needed to understand
the pathways of C13norisoprenoids