Flashcards in MTB 1: Post-Fermentation Operations Deck (88)
What causes the increase in VA?
The gradual oxidisation of aldehydes, producing acetic acid.
Ideal bulk storage temp. for red:
Between 10 and 20 degs, ideally 15.
Ideal bulk storage temp. for delicate whites and rosés:
Below 10 degs
Optimum humidity level:
Free SO2 levels needed to stop oxidation:
At least 20 mg/L
The amount by which a container falls short of being full.
Inert gases used for blanketing and prevention of spoilage yeast/bacteria:
Nitrogen (low solubility, used to sparge wine, removes dissolved oxygen, for reds), carbon dioxide (dense, dissolves well, whites) and argon (pricey).
Benefits of micro-oxygenation:
Reduction of herbaceous aromas, better structure, better oak integration, control of reduction.
Why do oxidatively aged wines become more concentrated?
Because of evaporation.
In biological ageing, ethanal degrades resulting in...
MLF - providing nutrients.
Too thick or unstirred lees can lead to...
Hydrogen sulphide or mercaptan odours.
Effects of small barrels (less than 500 litres):
Reduction of fresh aroma, early tannin polymerisation, stabilisation and clarification.
Two kinds of oak:
Red (not porous, no good for winemaking) and white (used for winemaking).
American, low phenols, high aromatics - oak lactone (coconut).
Quercus petraea (/sessiliflora):
European, tighter grained, less tannin, highly aromatic - eugenol (cloves), phenol aldehydes - vanillin (oak/vanilla).
Pendunculate (bearing a stalk with a flower/fruit), not particularly aromatic, but highly extractable polyphenols.
Typical barrel costs (225l barrique):
French: €600-€800, American €440.
Key oak origins (France):
Tronçais, Allier, Nièvre (central, v. tight grain), Vosges (NE) and Limousin (east of Cognac, tighter and tannic wood).
Oak origins (rest of Europe):
Russian, Hungarian, Slavonian (Italy) and Portuguese - cheaper.
Oak origins (USA):
Oregon, Minnesota and Wisconsin.
Sawing vs. splitting. European split along grain to avoid leakage. American can be sawn to maximise yield.
Air vs. kiln. Air-drying leaves less tannic wine. French oak usually left in air for 18-36 months.
Degrades wood structure, leaves aromatic compounds. Less toast: tannins and wood notes. More toast: toasty and spicy. Lack of seasoning can make wine sappy/astringent.
Shaving and re-charring:
Can add on 10 years more life, but leaves them more brittle and flavours rarely as subtle/well-integrated.
Adding oak chips:
Most effective when added during fermentation.