1. Wine defects Dr Kotseridis Yorgos

2. 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

3. 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

4. 1. Defects having origin on the grapes

5. Defects having origin on the grapes

6. (L-R): MPs:isobutyl- (IBMP); isopropyl- (IPMP); secbutyl- (SBMP)
Vegetative aroma
Methoxypyrazines (MPs) are intense and unique aromatic compound in wine
(L-R): MPs:isobutyl- (IBMP); isopropyl- (IPMP); secbutyl- (SBMP)

7. 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 15
5500

8. Vegetative aroma, cont’d
MPs in wine elicit of aromas of:
bell pepper, asparagus, peas, earthy, peanut
MPs are present in wine from:
grape-derived (Sauvignon varieties)
Cabernet, Merlot, Sauvignon Blanc, Carmenere, Semillon
insect-derived (MALB)
adulteration

9. Vegetative aroma, cont’d
Unique properties:
Concentration (ng/L)
Threshold (ng/L) MP
Grape-derived (Sauvignon)
Grape-derived (Other)
Insect-derived (10MALB/L)
Odour recognition threshold (wine) IB
(~ 1/4)
4.5-6
3-10: red1,2 IP
(~ 1/2)
30-38
2-1.03: red3,4
: white4 SB 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

10. 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)

11. MPs: decrease dramatically during ripening
light exposure and/or heat cause MP degradation
hence, elevated MPs correlated with low quality

12. 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)

13. 2. Defects having origin fermentation and processing

14. H2S

15. Sensory thresholds

16. 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 add 1 mL of 0.05 % CuSO4

17. Diagnostic test

18. Cellar treatment

19. Cellar treatment

20. 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

21. 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)

22. 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

23. 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 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

24. 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

25. Formation pathway

26. 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 ml/L active SO2) during ageing

27. 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

28. 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

29. Cork taint, cont’d To avoid:
avoid chlorinating via hypochlorite, some produces use alternatives
sensory analysis
additional treatments (ie., steam treatment)

30. Cork taint, cont’d

31. Cork taint Only a few bottles will be affected
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

32. 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

33. 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

34. Thank you