Wine off-flavorsWine 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 defectsDefects having origin on the grapesDefects 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’dGreat 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’dMPs 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’dUnique properties:

Concentration (ng/L) Threshold (ng/L)

MP Grape-derived (Sauvignon)

Grape-derived (Other)

Insect-derived (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

Time (weeks)

IBMP

(ng/L) Heat 2100 (C)

Heat (1430 (C)

0

10

20

30

40

50

60

70

80

0 2 4 6 8 10

Time (weeks) from January 1

MP

co

nce

ntr

ati

on

(n

g/L

)Cabernet SauvignonSauvignon Blanc

MPs: decrease dramatically during ripening

• light exposure and/or heat cause MP degradation

• hence, elevated MPs correlated with low quality

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

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 add 1 mL of 0.05 % CuSO4

Diagnostic test

Diagnostic test

Cellar treatment

Cellar treatment

3. Defects that take place during wine storage

Mainly caused by microbes Prevention of microbiological spoilage

Sulfur dioxideSterilizing filtrationThermal processing, partial pasteurisation

Avoiding microbiological contaminationsHygiene

OxydationMustiness, 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 productionProduction 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 productionAcetic 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 g/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 alternativessensory analysisadditional 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 notesWine contamination via atmosphereThe whole bottles of a batch will be affectedChlorophenols 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

GeosmineOccurrence 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

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