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Wine defects Dr Kotseridis Yorgos

Wine defects Dr Kotseridis Yorgos. 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

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Wine defects Dr Kotseridis Yorgos

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  1. WinedefectsDr 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. 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)

  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:

  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. Cellartreatment

  19. Cellartreatment

  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 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

  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 0.6-0.8 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 • 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

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