Wine off-flavors
 Wine
defects or wine faults are unpleasant
characteristics that affect wines aroma smell or
appearance
 It is easier to prevent spoilage than it is to fix it after it
has occurred
 However someone can improve the spoiled wine as
there plenty of new techniques
Type of wine defects
 Defects having origin on the grapes
 Defects that take place during fermentation and
processing
 Defects that take place during wine storage
 Defects that take place after the wine is bottled
1. Defects having origin on
the grapes
Defects having origin on the
grapes
Vegetative aroma
Methoxypyrazines (MPs) are intense and unique
aromatic compound in wine
(L-R): MPs:isobutyl- (IBMP); isopropyl- (IPMP); secbutyl- (SBMP)
Vegetative aroma, cont’d
Great biological significance, important in many
foods

Occurrence in common foods, below (in ppb)
Food
iso-propyl
sec-butyl
iso-butyl
asparagus
30
<5
-
beans
50
5
120
carrot
<10
250
-
lettuce
110
45
10
bell peppers
200
300
20000
chilis
110
15
5500
Vegetative aroma, cont’d
MPs in wine elicit of aromas of:
bell pepper, asparagus, peas, earthy, peanut
MPs are present in wine from:
1. grape-derived (Sauvignon varieties)
•
Cabernet, Merlot, Sauvignon Blanc, Carmenere, Semillon
2. insect-derived (MALB)
3. adulteration
Vegetative aroma, cont’d
Unique properties:
Concentration (ng/L)
Threshold (ng/L)
MP
Grapederived
(Sauvignon)
Grapederived
(Other)
Insectderived
(10MALB/L)
Odour recognition
threshold (wine)
IB
0.6-38.1
(~ 1/4)
4.5-6
3-10: red1,2
IP
0.9-5.6
(~ 1/2)
30-38
2-1.03: red3,4
1.56-0.32: white4
SB
0.1-1.5
nd
-
unknown
REFS
Lacey et al.,
1991
Hashizume et
al., 1999;
Romero et al.,
2006
Pickering et
al., 2005
1Romero
et al., 2006;
2Kotseridis et al.,
1998;3Maga,
1989;4Pickering et al.,
2007
Changes of isobutylMP in Sauvignon Blanc
towards ripening at 2 climatic regions in Australia
IBMP
(ng/L)
Heat 2100 (C)
Heat (1430 (C)
Time (weeks)
80
MP concentration (ng/L)
70
Cabernet Sauvignon
Sauvignon Blanc
60
50
40
30
20
10
0
0
2
4
6
8
Time (weeks) from January 1
MPs: decrease dramatically during ripening
• light exposure and/or heat cause MP degradation
• hence, elevated MPs correlated with low quality
10
Off-flavors due to various rot
 Fungus off-flavor; grapes affected by grey mold
(Botrytis cinerea) often associated with other molds
 Harvest happens latter and latter with sometimes bad meteorological
conditions
 Involved compound
 Geosmine : earthy, humus, camphor (Darriet et al., 2000)

Perception threshold : 10 ng/L
 1-Octene-3-one : mushroom, métallic

perception threshold : 20 ng/L (white wine)
2. Defects having origin fermentation and
processing
H2S
Sensory thresholds
Diagnostic test
 Step one fill 3 glasses with 50 ml of wine
 Glass 1 control, not any addition
 Glass 2, add 1 mL of 0.05 % CuSO4
 Glass 3, add 2 mL of 1% ascorbic acid and after 15 min
mL of 0.05 % CuSO4
add 1
Diagnostic test
Cellar treatment
Cellar treatment
3. Defects that take place during wine storage
Mainly caused by microbes
 Prevention of microbiological spoilage
 Sulfur dioxide
 Sterilizing filtration
 Thermal processing, partial pasteurisation
 Avoiding microbiological contaminations
 Hygiene
Oxydation
 Mustiness, an olfactive defect
 Different of the « rancio » character.
 Oxydated compounds may appear in aerated wine
 Aroma of recently cut apple due to free ethanal (acetaldehyde)
 Risks during racking, bottling and sampling
 Prevention by maintening adequate free SO2 levels and regular topping up
(every 8 to 15 days during barrels ageing)
Acetic acid production
 Production of volatile acidity by bacteria
 After AF et MLF : normal levels around 0,40 g/L of acetic acid
 Limits EU : white and rosé wines : 1,04 g/L acetic acid ; red wines : 1,20 g/L
acetic acid
 Generally when VA<0,72 g/L acetic acid : wine flavour is not affected
 Lactic acid bacteria and lactic spoilage
Acetic acid production
 Acetic acid bacteria
 Ethanol oxydation followed by acetic acid esterification to produce ethyl
acetate « acescence »
 Ethyl acetate is not detected when lower than 120 mg/L ; when higher than
à 160 -180 mg/L : solvant – glue, burning notes
 Acetic spoilage
 Linked to storage conditions
 O2 and température are key points
 Acetic acid bacteria are always present in wines
Volatiles phenols in red wines
 Apparition during post fermentation maceration
and ageing
 4-Ethylphenol : leather, horse’s sweat, stable
 4-Ethylgaiacol : spicy, smoked
 Preference threshold, mixture 10/1 : 420 mg/L
Chatonnet et al., 1992, 1995
Formation pathway
Prevention of this spoilage
 Factors favorising
 In the vineyard, presence of Brettanomyces ; distillery pomace ; wet zones ;
surmaturation?
 High pH, stuck fermentations, omission of racking, micro-oxygenation, …
 Monitoring by tasting and chromatographical analyses
from the end of fermentation and during ageing
 Keeping appropriate free SO2 level (ideally at least 0.6-
0.8 ml/L active SO2) during ageing
Prevention of this spoilage
 Barrels hygiene : regular cleaning and sulphuring up to
10g for a 225L barrel
 Process applied to wine:
 Flash-pasteurisation (after AF and beginning of ageing)
 Sterilizing filtration (before bottling)
 Chitosane
4. Defects that take place after the wine is
bottled - Cork Taint
• moldy/musty/smoky off-flavor, aroma
• distinguish from microbial fault in wine due to bottle variation
Estimation: 2-6% corktaint of all bottles under natural cork
• Main chemical responsible: 2,4,6-trichloroanisole (TCA)
•Threshold is 4-10 ng/L
Cork taint, cont’d
To avoid:
 avoid chlorinating via hypochlorite, some produces use
alternatives
 sensory analysis
 additional treatments (ie., steam treatment)
Cork taint, cont’d
Cork taint
 Formation : transformation by molds of chlorinated compounds used for tree
treatment, cork preparation and stopper elaboration (surface treatment)
 Only a few bottles will be affected
Mouldy notes
 Wine contamination via atmosphere
 The whole bottles of a batch will be affected
 Chlorophenols have been used for wood protection
(pallet, roof support, …)
 Bulk wine and enological products (filter plates, fining
agents, bentonites, corks,…) may be polluted
 Involved compounds
 2, 4, 6 Trichloroanisole (TCA) : mouldy, wet cardboard
Perception threshold in water: 0,3 ng/L
 2, 3, 4, 6 Tétrachloroanisole (TeCA) : mouldy
 Perception threshold in water : 4 ng/L
 2, 4, 6 Tribromoanisole (TBA) : mouldy, sometimes phenol or iodine
 Perception threshold in water : 2 ng/L

Geosmine
 Occurrence of Penicillium expansum, associated with
Botrytis cinerea (that prepare the medium for
geosmine production)
 In the vineyard, this defect may appear in less than 10
days
 This compound is stable during alcoolic fermentation
and ageing (20%)
 May be removed by heating (80% at 70°C for 24h)
La Guerche et al., 2004
Thank you