Ch 7 - Oxygen Effects And Sulphur Dioxide Flashcards
Why would a winemaker wish to control all the steps in winemaking?
To achieve a particular stylistic goal e.g. a wine dominated by primary fruit flavours.
A wine made with little or no human intervention is often known as a ….. wine?
A natural wine.
Is oxygen a threat or aid in winemaking?
It can be both depending on the style of wine being made.
When is oxygen a threat?
If a winemaker is seeking a wine dominated by primary fruit flavours oxygen needs to be countered.
How might oxygen effects be countered in winemaking if required?
Use of an antioxidant such as SO2 to minimise o2 contact;
Picking grapes at night when it is cooler and o2 effect is reduced by lower temperatures;
Chill grapes until they reach the winery;
Using airtight equipment filled with nitrogen or CO2 - “anaerobic winemaking”;
Picking whole bunches avoiding any damage and exposure to o2.
How are anaerobic wines stored?
They dont benefit from any contact with oxygen during maturation so are stored in inert, airtight vessels made from stainless steel or cement lined with epoxy resin.
How are wines which can benefit from oxygen stored?
Normally in wooden vessels made of oak. These are watertight but not airtight and allow small amounts of oxygen to permeate and react with the wine.
What effect can oxygen have on wines during maturation?
Small amounts of O2 can soften tannins ( red wine);
Add complexity to the flavours - primary flavours fade and tertiary flavours develop;
There may be colour change - red becomes paler towards garnet, and white becomes deeper in colour towards orange.
What determines the effect of oxygen on the wine?
Size of the vessel and length of time wine is stored in it.
What size of vessel has most impact on the wine?
Smaller 225- litre “barriques” have greater effect than larger vessels as a proportionately larger amount of wine is exposed to the wood.
How long would wine usually be stored in small or large barrels respectively?
Small rarely longer than two years;
Large longer periods
What is “ullage”? When might it be used?
This is a technique whereby the barrel is not filled completely with wine leaving more space for oxygen at the top of the barrel. It is used in some deliberately oxidative styles of fortified wines such Oloroso, Tawny Port and Rutherglen Muscat.
What character does additional oxidative exposure add?
Tertiary characteristic of caramel, toffee and nuts.
What are two main effects of SO2?
It acts as:
* an antioxidant;
* an antiseptic.
It is almost indispensible in the winery.
How is SO2 used as an antioxidant?
To protect freshly harvested grapes, juice and wine against the effects of oxidation. Once used it is “bound” and must be constantly monitored and levels replenished to ensure ongoing protection.
