Understand wine AROMAS

Question 1

What typical aromas characteristics does light oak toasting express in wines?

Answer 1

• Vanilla
• Nutmeg
• Clove

Question 2

What typical aromas characteristics does medium oak toasting express in wines?

Answer 2

• Caramel
• Cigar box
• Chocolate

Question 3

What typical aromas characteristics does heavy oak toasting express in wines?

Answer 3

• Tobacco
• Coffee
• Smokiness

Question 4

What impact compound causes wines to express aromas of:

(black) pepper

also often expressed with the discriptors ‘white pepper’, ‘spice‘, ‘Marjoram’, ‘Leathery’ and ‘Cocoa Powder’

Answer 4

Rotundone, a Sesquiterpene, part of the class of terpenoids. This highly diverse class of natural products gives highly floral flavours to Muscat, more subtal floral and citrus aromas to Riesling and red berry-like and savoury characters to red wines.

• Most panellists sniffing for rotundone’s distinctive aroma could detect it at very low levels, a fifth of the panel were unable to smell it at all
• Research suggests that Rotundone might be involved in the vine’s natural defense mechanism in response to powdery mildew attacks

Question 5

In (wines of) which cultivars are peppery aromas typically found?

Answer 5

Rotundone has been detected in the exocarp (skin) of:

• Syrah | Shiraz (were it was initially identified by AWRI)
• Grüner Veltliner
• Pinot Noir
• Cabernet Sauvignon
• Gamay
• Graciano
• Durif
• Mataro
• Pineau d’Aunis
• Schioppettino
• Vespolina

Question 6

What viticultural, environmental and winemaking practices drive the formation of Rotundone in vine berries and expression of this aroma in wines?

Answer 6

• Cooler vintages / vineyards
• Specific clones (shows clonal differences)
• Not impacted by grape thinning
• Strongly lowered by leaf removal, berry shading to improve it.
• Enhanced by irrigation
• Mostly extracted in days 2-5 of fermentation (very active ferment phase, increasing ethanol)
• Enhanced by inclusion of grape leafs and stems in fermentation
• significantly lost in separation, filtration a/o fining (probably due to its hydrophobic nature)
• Low in Thermo vinification and Rosé techniques
• Not favoured by Pre-fermentation heat treatment and semicarbonic maceration

Question 7

Are peppery aromas more pronounced in cooler or warmer vintages?

Answer 7

Cooler vintages

Rotundone - the impact compound causing the peppery aroma - is most likely to accumulate in grapes in cooler vintages and in cooler vineyards and is formed in berries during the ripening phase post-veraison.

Question 8

What impact compound causes wines to express aromas of:

eucalyptus

also often expressed with the discriptors ‘fresh’, ‘cool’, ‘medicinal’, ‘minty’ and ‘camphorous’

Answer 8

Eucalyptol or 1,8-cineol, is an achiral aromatic component of many plants, such as salvia and eucalyptus leaves.

Question 9

What is the origin of the impact compound causing an eucalyptus aroma in (only) red wines?

Answer 9

Research by the AWRI has shown that the origin of Eucalyptol is from Eucalyptus trees adjacent to the vineyards. Studies confirmed that it was vineyard position that had the most profound effect on 1,8-cineole concentration in red wine, and although aerial transfer was important, the most significant effect was observed when a small quantity of Eucalyptus leaves from nearby trees was present in the harvested grapes

The theory of Eucalyptol being formed from the precursors Lemonen and alpha-terpineol was proved not to hold ad thus was rejected.

Question 10

What viticultural, environmental and winemaking practices drive the formation of Eucalyptol aroma in red wines?

Answer 10

• (Not) planting eucalyptus trees in the proximity of vineyards
• Harvesting & vinifying vine rows within 5-20m of Eucalptus trees separately and blend back in as desired

Question 11

Wines in which regions can be expected to express Eucalyptus aromas?

Answer 11

Th Eucalyptus tree being native to Australia means that especially Australian wines can express Eucalyptus. A survey of 190 commercial Australian red wines revealed that 40% of the wines analysed contained 1,8-cineole at or above its reported aroma detection threshold.

Note that the Eucalyptus tree is native to Australia, but has spread to every continent since. Many wines from other regions are known to express Eucalyptus notes. Some Chilean and Californian Cabernet Sauvignon are good examples.

Question 12

What impact compound causes wines to express aromas of:

cooked apple

also often expressed with the discriptors ‘rose’ or ‘honey’

Answer 12

β-damascenone, a C13-norisoprenoid, a class of compounds given considerable attention by researchers due to their intriguing range of aroma characteristics, from ‘floral’ and ‘fruity’ to ‘petrol’ and ‘fly spray’.

Alongside the pleasant aroma descriptors, β-damascenone has also been found to act as an aroma enhancer for ethyl esters associated with berry fruit aroma and to have the ability to mask herba- ceous methoxypyrazine-related characters

Question 13

In (wines of) which cultivars are (cooked) apple aromas typically found?

Answer 13

β-damascenone does not appear to be connected to particular grape cultivars as it is often found in wines of most grape cultivars above threshold.

In general, the concentration appears to range between 2–5 μg/L and ∼ 1 μg/L in young and aged wines, respectively. Interestingly, in studies Cabernet Sauvignon had the highest median concentration (7.8 μg/L) of all grape cultivars, except for one example of 42 μg/L found in Muscat.

Question 14

What viticultural, environmental and winemaking practices drive the formation of β-damascenone aroma in wines?

Answer 14

• Leaf removal cannot be considered to necessarily lead to increased β-damascenone in grapes
• Timing of exposure is likely an important factor which requires further investigation, including assessing the effect across cultivars.
• Water deficiency has also been found to increase bound β-damascenone concentration in both Merlot and Cabernet Sauvignon grape berries.

Question 15

What impact compound causes wines to express aromas of:

kerosene or petrol

in France also known as Goût-de-Pétrol

Answer 15

TDN or 1,1,6,-trimethyl-1,2-dihydronapthalene is one of the more polarising, and also most heavily studied, C13-norisoprenoids. At low levels TDN is desirable and delicious, but at a high concentration, TDN can dominate the wine and become an off character that exerts negative sensory attributes to the wine, incurring consumer rejection

Question 16

What is the origin of the impact compound causing a Petrol or Kerosene aroma in (only) red wines?

Answer 16

The quantity of TDN is close to zero at harvest and increases with wine aging due to the hydrolysis and rearrangement of TDN precursors over time. Exposure to sunlight and warmer climate would increase the level of TDN precursors up to 2-4 folds.

Question 17

In (wines of) which cultivars are Petrol / Kerosene aromas typically found?

Answer 17

It exist in highest quantities in aged Riesling wines, reaching as high 50ug/L.

Though it is also widely prevalent in Chardonnay, Sauvignon Blanc, Pinot noir and Cabernet Sauvignon at levels close to its sensory threshold of 2ug/L, with exception of 6.4ug/L in Cabernet Franc.

Question 18

What viticultural, environmental and winemaking practices drive the formation of TDN aroma in wines?

Answer 18

TDN concentrations in both red and white wines can be increased by sunlight exposure and leaf removal. Generally, exposure to sunlight after veraison was able to increase TDN concentration to the greatest extent.

Longer storage time, higher storage temperature and lower wine pH were discovered to favor TDN formation.

With the impact of global warming, TDN is raising more concerns relating to wine quality and its level needs to be controlled.

Question 19

What impact compound causes wines to express aromas of:

Green bell peper (Capsicum)

also often expressed with the discriptors ‘Fresh Cut Grass’, ‘Green Peppercorn’, ‘Asparagus’ and ‘Pea’

Answer 19

IBMP one of 3 primary methoxypyrazines which contribute “vegetal” aromas:

1. 2-methoxy-3-isobutylpyrazine (IBMP) giving earthy, grassy, and green bell pepper aromas;
2. 2-methoxy-3-isopropylpyrazine (IPMP) giving aromas of asparagus, peas, and earth; and,
3. 2-methoxy-3-alkylpyrazine with gives roasty and nutty aromas.

Most wine drinkers find this compound class to be a positive trait in white wines but a negative one in red wine.

Question 20

What is the origin of the impact compound causing a @@@@ aroma in wines?

Question 21

What viticultural, environmental and winemaking practices drive the formation of pyrazine aroma in wines?

Question 22

In (wines of) which cultivars are @@@@ aromas typically found?

Answer 22

Pyrazines are most commonly associated with Bordeaux-origin varieties:

• Cabernet Franc
• Cabernet Sauvignon
• Merlot
• Malbec
• Carménère
• Sauvignon Blanc

Question 23

Wines in which regions can be expected to express @@@ aromas?

Question 24

What impact compound causes wines to express aromas of:

passion fruit

also often expressed with the discriptors ‘box hedge’, ‘grapefruit’ and ‘tropical’

Answer 24

The varietal thiols:

• 3-mercaptohexanol (3-MH), giving grapefruit aroma
• 3-mercaptohexyl acetate (3-MHA), giving passion fruit aroma
• 4‐mercapto‐4‐methylpentan‐2‐one (4-MMP), giving buxus, box hedge aromas.

Question 25

What is the origin of the impact compound causing a passion fruit | box hedge | grapefruit aroma in wines?

Answer 25

Varietal thiols in wine are produced during fermentation, from thiol-amino acid conjugates, the odourless precursors that form in the grapes, especially after crushing, following any skin contact or with Botrytis infection.

Question 26

What viticultural, environmental and winemaking practices drive the formation thiol aroma in wines?

Question 27

In (wines of) which cultivars are passion fruit | box hedge | grapefruit aromas typically found?

Question 28

Wines in which regions can be expected to express passion fruit, box hedge or grapefruit aromas?

Question 29

What impact compound(s) causes wines to express aromas of:

Band aid medicinal

also often expressed with the discriptors ‘Barnyard’, ‘Sweaty saddle leather’, ‘Burnt plastic’, ‘Savoury’, ‘Animal’ and ‘Smoky bacon’.

Answer 29

Brett compounds are usually always present together, albeit in different amounts or ratios to each other:

• 4EP, 4-ethylphenol, or the Band-aid aroma, is the main contributor and is considered the general ‘marker’ for Brett.
• 4-EG, 4-ethylguaiacol adding smoky and spicy notes,
• 4-EC,4-ethylcatechol adding savoury, smoky bacon, sweaty/cheesy and barnyard/animal nuances.

The palate can also be affected; with diminished fruit flavour intensity and a drying and metallic aftertaste. Note that as a wine ages, primary fruit flavours reduce; this can also start to reveal more strongly any Brett characters that might have been hiding away.

Question 30

What is the origin of the impact compound causing a Brett aromas in wines?

Answer 30

Brett compounds originate from Brettanomyces bruxellensis and it and other members of the Brettanomyces genus, often referred to collectively as “Brett”.

Brett is a type of yeast commonly found in wineries, which has the potential to cause significant spoilage in wines, through the production of volatile phenol compounds such as EP, EG and EC.

Question 31

What viticultural, environmental and winemaking practices drive the formation of Brett aroma in wines?

Answer 31

The growth of Brettanomyces is wine is affected by a range of factors, some of which are interlinked. This means that controlling Brett requires a multi-faceted approach. The key factors to address are:

• General sanitation
• Residual sugar
• pH and SO2
• Barrel sanitation and topping
• Filtration and clarification

The ‘Brett zone’ is now known to be the critical time between the end of primary and secondary fermentation until the point before sulfur dioxide (SO2) is added. Leaving wines unsulfured for long periods of time, particularly during slow malolactic ferments (MLF), is the riskiest time for Brett growth. Ideally, MLF should be finished quickly. A molecular SO2 concentration of 0.6 mg/L is required to prevent Brett growth, and is best achieved by one large addition of SO2 post-malolactic fermentation, rather than a number of smaller additions.

Question 32

In (wines of) which cultivars are Brett aromas typically found?

Answer 32

At one time it was commonly thought that all red wine has Brett, just in different amounts. In the late 1990s this was probably the case, nowadays Brett management techniques help to avoid Brett.

Wines have different ratios of Brett compounds, being related to the different levels of their precursors naturally present in different grape varieties.

Some typical ratios in varieties, and likely sensory effects compared to 4-EP alone, are shown below.

• Pinot Noir, 4-EP:4-EG=3:1, More leather and barnyard, spicy
• Cabernet Sauvignon, Nebbiolo, 4-EP:4-EG=9:1, sensory effect similar to 4-EP alone, but with a pungent spice
• Shiraz, 4-EP:4-EG=23:1, sensory effect similar to 4-EP alone, pure Band-Aid

Thus while a Brett-affected Shiraz might smell like pure Band-Aid, a Brett-affected Pinot Noir will possibly smell more ‘animal’, ‘barnyard’ and ‘spicy’, perhaps akin to and often confused with savoury characters of Pinot Noir wines and heavily toasted or spicy oak flavours.