Anita Oberholster Musty Taints. Introduction: Musty Taints What off-odours are classified as musty taints? – Fungal, earthy, moldy, corky, mushroom or

Anita Oberholster

Musty Taints

Introduction: Musty Taints• What off-odours are classified as musty

taints?– Fungal, earthy, moldy, corky, mushroom or

straight musty

• What causes musty taints?– Haloanisoles (TCA, TCB)– Alkylmethoxypyrazine (MDMP)– Carbon unsaturated aliphatic compounds with

carbonyl function (1-octen-3-one, 1-nonen-3-one)

– (-)-Geosmin

Musty Taint: Cork Taint• Cork taint caused by aroma intense compounds

in the cork transferring to the wine• Economic loss, estimates 1-5% of bottles

effected• Main contributor is

• Responsible for 80-85% of cork taint• Many times only compound analysed

2,4,6-trichloroanisole (TCA)

TCA• TCA taints sometimes from other sources

than corks– Contaminated processing aids– Oak barrels– Wineries with high background of these

compounds– Bottels

• Bottle to bottle variation indicate cork taint

Sefton and Simpson, Austr. J. Grape Wine Res. 2005, 11, 226-240.

TCA• ‘Musty’, ‘mouldy’, ‘wet cardboard’ character• Generally detection threshold given as 1.4-4.6

ng/L• Threshold varies substantially among individuals– 1 –250 ng/L (white wine) experienced panellists,

group threshold 17 ng/L– 2.5 –250 000 ng/L (white wine) inexperienced

panellists, group threshold 210 ng/L– 1-2 ng/L experienced judges

• TCA chemically stable, will not degrade over time


Other Chloroanisoles• Frequently detected with TCA:– 2,4-dichloroanisole (2,4-DCA) – 2,6-dichloroanisole (2,6-DCA) – 2,3,4,6-tetrachloroanisole (TeCA)

– Pentachloroanisole (PCA) • TCA always most important contributor

TeCA2,4-DCA 2,6-DCA PCA

Origin of Chloroanisoles• Origin of chloroanisoles in cork– Already present in bark of living cork trees

• 2,4,6-trichlorophenols (TCP) produced from naturally-occuring phenols and chlorine from sanitizers, cleaning products and town water

• Chlorine-bleaching treatments of cork, now mostly discontinued

• Chlorophenol biocides accumulated in environment• Microorganisms capable of methylation are present in cork,

form TCA from TCP

– Decline of TCA in corks• Suggest depletion of source of contamination

Sefton and Simpson, Austr. J. Grape Wine Res. 2005, 11, 226-240.Simpson and Sefton, Austr. J. Grape Wine Res. 2007, 13, 106-116.

Origin of Chloroanisoles• Co-occurence of TCA with other chlorine-

compounds – If co-contaminants contain fewer chlorine-atoms –

indicate sources as town water, sanitizers or bleaching agents

– If co-contaminants contain higher number of chlorine-atoms indicate PCP or TeCP-based biocides

– Presence of both indicate multiple TCA-producing pathways

Simpson and Sefton, Austr. J. Grape Wine Res. 2007, 13, 106-116.

Transmission from Cork to Wine• Transmission depend on several factors:– Solubility of taint compound in wine– Affinity of taint compound for cork surface and

interior– Location of taint compound on cork– Rates of taint compound migration through cork– Volume of wine in contact with closure

• Only TCA have been studied in detail– All discussion - according to TCA findings


Transmission from Cork to Wine• TCA – high affinity for cork– Corks soaked in contaminated wine will absorb TCA – Only small amount of TCA in cork extracted into wine

• TCA can contaminate outside of cork closures, but does not migrate through cork

• Contamination only from part of cork in contact or close proximity to wine

• Formation of TCA in situ have been suggested– Experiments show no conversion of TCP to TCA

in bottle (Liacopoulos et al., 1999)

Capone et al., Austr. J. Grape Wine Res. 2002, 8, 196-199.Sefton and Simpson, Austr. J. Grape Wine Res. 2005, 11, 226-240.

Screening for Chloroanisoles• Screening method usually based on sensory

assessments of wine soaks or corks in damp environment– Advantage – low cost, detect both known an

unknown taints– Disadvantage – variation in performance of assessors– Low sensitivity and corks soaked in batches– Soaked few hrs to 2 days in mostly aqueous alcohol

• Instrumental analysis of TCA – Identify specific taints as well precursors


Screening for Chloroanisoles• No screening method reflects accurately level of

taint in bottle– Whole surface of cork is extracted in cork soaks– Short soaking periods means only ‘rapidly released’

TCA measured– Batches soaked, if one cork contaminated the average

could be below detection limit

• However, these measurements still help predict bottle taint


Screening for Chloroanisoles• TCA contaminated corks detected (1%), much

lower than incidence of cork taint observed (5%)– Underestimation during cork assessment– Short duration of extraction (24-48 hrs)– Presence of usually 5 corks per soak and small vol of

wine

• Despite limitation of methods, badly contaminated corks will be detected


Removal of Chloroanisoles• TCA diminished by aeration– Accelerated by high moisture content and heat

• Steam-cleaning removes 75-80% of rapidly releasable TCA– Bottle trials show good results

• Supercritical carbon dioxide extraction– AWRI found no TCA transfer to wine after 2 years

using these closures

• Other techniques designed to diminish TCA– Microwave treatment– Enzymes– Use of physical barriers

Tribromoanisole (TBA)• 2,4,6-Tribromoanisole (TBA) identified in tainted

wine• ‘Musty or corked’ character• Detection threshold of 4 ng/L• Produced by microbial breakdown (O-

methylation) of precursor 2,4,6-tribromophenol (TBP)

Chatonnet et al., J. Agric. Food Chem. 2004, 52, 1255-1262.

TBA

Sources of TBA• Similar to TCA, plastic material in general readily

absorb TBA and to lesser extent TBP• Polyethylene- or polyester-based winemaking

equipment, silicon bungs etc. contaminated• Wineries with TBA problems– Wooden timbers massively impregnated with TBP– Some paints also contained TBP

• TBP used as flame retardant or/and fungicide


In summary TCA/TBA• Both TCA and TBA have low detection threshold• Distinctive ‘musty and/or corky’ character• Screening methods useful in prediction of bottle

taint although not absolute• Effective methods available to remove

contaminants from cork• Incidence decreasing as sources of

contamination depletes

Musty Taints: Alkylmethoxypyrazines

• ‘Wet cork’ or ‘corky’ character, ‘fresh hazelnut’ or ‘herbaceous’ character and ‘moldy’ or ‘earthy’ character at high concentrations

• Detection threshold of 2.1 ng/L• Measured in affected wines, 1.4 – 3.5 ng/LChatonnet et al., J. Agric. Food Chem. 2010, 58, 12481-12490.Simpson et al., Agric. Food Chem. 2004, 52, 5425-5430.

2-Methoxy-3,5-dimethyl-pyrazine (MDMP)

Formation of MDMP• Several microorganisms able to synthesize

MDMP– Serratia odorifera , C. crocatus, and R. excellensis

• Biosynthesize from amino acids not well-known– The alanine amide condenses with methylglyoxal

(pyruvaldehyde) to form 2-hydroxy-3,5—DMP, which after methylation produces MDMP

• L-alaine and L-leucine responsible for highest conc of MDMP– Lesser extent L-valine and phenylalanine


Source of Contamination• Corks– Cutting punches used for cork cylinders possible

source of taint– Opposite to TCA, it has low affinity for corks and

easily extracts into wine– High contamination levels, 86% corks tested > 2ng/L– Corks < 5 ng/L, (34.9 %) minimal risk– Batches with 5.1-15.0 ng/L, medium risk (51.2 %)– Batches with > 15.1 ng/L , extreme risk (16.3%)

Chatonnet et al., J. Agric. Food Chem. 2010, 58, 12481-12490.Simpson et al., J. Agric. Food Chem. 2004, 52, 5425-5430.

Source of Contamination• Oak– Found wine contaminated with MDMP, in vats with

oak chips, none found in same wine without oak chips

– Wood used for industrial wood chips stored on ground, possible source of MDMP

– Microorganisms found in soil that produce MDMP– MDMP destroyed by heat, 220 °C remove 93%– Untoasted and lightly toasted oak may contain

MDMP– Heat at 105 °C for 10 min only removes 50% of

MDMP


In summary MDMP• R. excellensis microorganism primarily

responsible for MDMP in cork• Both cork and oak are sources of contamination• Decontamination techniques– Similar to TCA removal– Lower affinity for cork, higher removal

• MDMP > 10 ng/L in 40% of corks• Systematic monitoring needed similar to TCA • Origin of microorganism– Likely storage of raw material near soil

Other Musty Taint Compounds• Three compounds detected in cork taint wines

other than haloanisoles or MDMP– Geosmin (‘earthy’ character)

• Detection threshold 25 ng/L

– 2-Methylisoborneol (‘earthy/musty’ character)• Detection threshold 30 ng/L

– 1-Octen-3-one (‘mushroom’ character)• Detection threshold 20 ng/L

La Guerche et al., J. Agric. Food Chem. 2006, 54, 9193-9200.Pons et al., J. Agric. Food Chem. 2011, 59, 3264-3272.Sefton and Simpson, Austr. J. Grape Wine Res. 2005, 11, 226-240.

• Primary cause of musty taints

• TCA and TBA

• MDMP

• Contributor to musty taints

• 1-Octen-3-one

• 1-Methylisoborneol (possibly degrades)

• Geosmin (possibly degrades)

• Small contributor to musty taints

• 2,4-DCA, 2,6-DCA, TeCA, PCA

• VA, ethyl acetate, H2S and ethanethiol, acetaldehyde, volatile phenols, mousy

Concluding remarks

Contact details

• Anita Oberholster– RMI North, room 3146– [email protected]– Tel: (530) 754-4866– http://wineserver.ucdavis.edu– http://enologyaccess.org

Documents

Anita Oberholster Musty Taints. Introduction: Musty Taints What off-odours are classified as musty taints? – Fungal, earthy, moldy, corky, mushroom or