11. Wine Components Flashcards
Where do the compounds that make up wine come from?
- Some come directly from the grapes
- Some are formed during the fermentation process
- Some are added during winemaking
Approximately what percent water by volume is wine? What does this depend on?
85%
- abv
- level of residual sugar
What are the 7 main compounds found in wine?
- Water
- Alcohol
- Acids
- Aromatic Compounds
- Residual Sugar
- Glycerol
- Phenolics
What is the predominant alcohol found in wine?
Ethanol
When does ethanol in wine form?
During fermentation
Describe what ethanol adds to a wine.
- slightly sweet smell
- sweetness
- bitterness
- oral warmth
- adds to body & mouthfeel
What is a considered a high alcohol abv? What does high alcohol add to the wine? What is required to balance this high alcohol?
- > 14.5% abv
- contributes to body and mouthfeel
- increase the sense of bitterness ,
- reduces volatility of flavours
- requires sufficient fruit concentration to be in balance
What are the 2 principal acids of wine? What are other 2 acids?
Principal: - tartaric acid - malic acid Other: - lactic acid - acetic acid
Where do tartaric and malic acid originate?
In the grapes
Where do lactic and acetic acid originate?
Produced during fermentation or malolactic conversion
In warm climates, what percentage of wine acid do tartaric and malic acid account for?
2/3 of the total acidity in wine
What is volatile acidity? What does it smells like?
- present in all wines, generally in low concentrations, and is only a fault when in excess
- mainly refers to acetic acid
- vinegar smell
What does volatile acidity smell like?
vinegar
What is referred to by the term Volatile acidity and how does this evolve into a fault.
Volatile acidity generally refers to acetic acid
- reacts with alcohol to becomes ethyl acetate
- nail varnish remover smell
- ethyl acetate is fault when in excess
What does acidity contribute to wine?
- contributes to structure
- makes wine refreshing
- should be in balance with fruit (and residual sugar when applicable)
What happens when there is is too much acid? Too little acid?
- Too much: Tart
- Too little: Flabby
What commonly comes into play when perceiving acidity? Give an example.
- Balance of acidity and residual sugar
- Example: some German Rieslings taste dry despite having significant levels of residual sugar (up to around 9 g/l) because of the elevated level of acidity.
Give an example of a wine with high levels of malic acid and how those levels affect the style.
By contrast what is the effect of malic acid conversion
Cool climate Chardonnay where the malolactic conversion has been blocked
- Firm acidity profile
Malic acid conversion reduces the malic acid level in the wine (it is converted to lactic acid). The over all acid level decreases (softer), complexity in the wine increases with aromas of butter from the lactic acid.
Are total acidity and pH correlated in wine? Why or why not?
- Linked, but not exactly correlated
- Buffering effect of other molecules (e.g. potassium).
- A wine with high acidity would usually have a low pH, and vice versa
How is acidity most commonly measured?
- ‘total acidity’, the sum of all the acids
- grams per litre (g/l) in tartaric acid
In France
if expressed as Sulfuric Acid the convers is 1 : 1.15
What is the typical range of total acidity in a wine?
- 5.5–8.5 g/l.
How is acidity commonly measured in France?
- expressed as ‘sulfuric acid’
- the ratio between sulfuric acid and tartaric acid is 1:1.5
What is pH?
- PH measures concentration of the effective acidity of a solution
- inverse scale: the lower the number the more concentrated the acidity
- logarithmic scale: a pH of 3 is ten times more acidic than a pH of 4
What is the typical pH range of wines?
3-4
What does a low pH mean for the wine? What does it mean for red wines?
- Increases the microbiological stability of wine
- Increases the effectiveness of SO2
- enhances a wine’s ability to age well
- Gives red wines a bright red colour
What are the 4 sources of aromatic compounds?
- Aromas from the grapes
- Aromas created by fermentation due to the presence of aroma precursors in grape must
- Aromas originating from fermentation and its by-products
- Aromas from other sources
Name 2 aromatic compounds found in grapes. What aromas does it give off? Give an example of a grape in which the compound is found.
- Methoxypyrazines: grassy, green pepper aroma (Sauvignon Blanc)
- Rotundone: pepper aroma (Syrah, Grüner Veltliner)
What are aroma precursors?
Compounds that are not in themselves aromatic but are building blocks which become aromatic during fermentation
Name 2 aroma precursors found in grapes. What aromas do they give off? Give an example of a each, and name a grape variety in which they are found.
- Thiols
- - Example: 4MMP, gives the box tree aromas (Sauvignon Blanc) - Terpenes: give fruity and floral aromas
- - Examples: linalool, geraniol, contribute to the grapey aromas/flavours (Muscat)
Name 4 aromas that originate during fermentation.
- Esters
- Acetaldehyde
- Diacetyl
- Reductive Sulfur
What are esters? What types of aromas are they responsible for? In what types of wines are esters most important?
- Compounds formed by the reaction of certain acids and alcohols during fermentation
- Most created through the action of yeasts
- Most unstable; breakdown a few months after fermentation
- Aromas: fresh and fruity (banana (isoamyl acetate), apple, pineapple, etc.)
- essential in young wines, mostly white
What is the most common ester? What aroma does it give off? Give an example.
- isoamyl acetate
- banana (when its concentration is high)
- Example: Beaujolais Nouveau
Name another common ester.
- ethyl acetate
What is acetaldehyde? What aromas does it give off? Give an example of a wine in which acetaldehyde is important.
- Occurs in wines due to the oxidation of ethanol.
- AKA ethanal
- masks fresh fruit aromas
- stale smell
- regarded as a fault in most wines
- Distinguishing aroma for Fino sherry
What is diacetyl? What aromas does it give off?
- Produced during fermentation, especially malolactic conversion
- Buttery aroma
Describe how reductive sulphur compounds might form and smell.
Form:
- produced by yeast during fermentation and lees aging
Smells:
- struck match (could be desirable)
- rotten eggs (fault)
What is vanillin? What aromas does it give off?
- aromatic compounds derived by ageing wine in new oak barrels
- vanilla
What is eucalyptol and how can it get into wine?
- volatized from eucalyptus trees by heat
- absorbed in the waxy layer of the skins of grapes in nearby vines
Describe Vincente Ferreira’s model for wine aromas.
There are 4 types of wine aromas:
- Compounds common to all wines
- aromas products by fermentation
- e.g. ethanol, high alcohols, some acids (acetic)
- slightly sweet, pungent, alcoholic, little fruity - Impact aromas
- specific aromas that can be recognized
- e.g. rotundone, 4MMP - Contributory aromas
- aroma compounds that are below their normal individual perception threshold but make a contribution when they are with certain other compounds
- e.g. ethyl acetate (fruity note at low levels)
- e.g. vanillin (vanilla) - Nonvolatile Wine Matrix
- the nonvolatile components of wine that affect the way the aromatic compounds are sensed
How much residual sugar is found in dry wines?
small amount of RS (2–3 g/l)
How much residual sugar is found in Sauternes? Pedro Ximenez sherry?
- Sauternes: 150 g/l
- Pedro Ximenez: 400 g/l
In addition to sweetness, what does RS add to w ine?
body
Does the sweetness level have to appear on labels in the EU?
No
Give an example of a EU wine region that encourages using sweetness codes on labels.
Alsace
What 2 factors does the EU classification for sweetness take into account?
- levels of residual sugar
- optionally higher levels of RS for wine with higher total acidity (goal is to guide consumers to the taste of the final wine)
What are the 4 levels of sweetness classification in the EU? And their related levels
- Dry/sec/trocken
- Up to 4 g/l RS
OR
- not exceeding 9 g/l if total acidity is not more than 2 g below RS content - Medium dry/demi-sec/halbtrocken
- 4 g/l - 12 g/l RS
OR
- up to 18 g/l provided that the total acidity is not more than 10 g below the RS content - Medium or medium sweet/moelleux/lieblich
12 g/l - 45 g/l RS. - Sweet/doux/süss
>= 45 g/l RS
What is glycerol? What does it add to the wine?
- derived from the sugar in grapes
- adds
- smoothness to the texture of wine
- perception of the fullness of the body
- slightly sweet taste
In what types of wines does glycerol occur in higher levels?
- botrytis-affected grapes (e.g. Tokaji)
- carbonic maceration (Beaujolais) - lesser
What are phenolics?
- Includes anthocyanins and tannins
- compounds that occurs in grapes, especially in the skins, stems and seeds
What are anthocyanins?
Colour pigments responsible for the red colour – and sometimes blue tints – of red and rosé wines
What are tannins?
- phenolic compound
- bind with proteins in the mouth, giving a drying sensation on the palate
When are tannins perceived softer / more astringent?
- Softer: A little residual sugar
- More astringent: Dry wines with high acidity
What do unripe tannins taste like?
- bitter
- never desirable
