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 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

(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)

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

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

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 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)

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

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

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 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

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

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