Vinification Flashcards
What does malolactic conversion do to a wine?
Decreases acidity, increases PH
softer acid, can give buttery/creamy texture
What does lees ageing do to red wines, and what is a possible disadvantage (of lees ageing for red wines)
Can help soften tannins in red wines
Poss disadvantage is reduced colour intensity
Not typical to keep gross lees or stir the lees when making red wines
What are the 3 key ways of making rose wines?
Direct pressing
Short maceration
Blending
Why is malolactic conversion usually avoided in the production of rose wines?
Buttery flavours are not wanted, would mask the fresh fruit aromas that are appealing to these wines
Designed to be refreshing to drink and therefore winemakers looking to retain acidity
When does blending most often occur
Can be carried out at any time during winemaking process, most often prior to finishing and packaging
Blending may involve combining wines …. (5)
- From different grape varieties
- Different locations (from different vineyards, regions or countries)
- Different vintages
- that have been treated differently in winery (i.e. press juice/free-run juice, matured in oak/stainless steel or concrete
- treated equally in winery but different vessels for logistical reasons (fermented or matured in barrels need to blend together to make up quantities)
What does PDO stand for and what does it mean for the grapes
Protected Designation of Origin
100% of the grapes must come from the defined geographical area
What are the 7 key reasons for Blending a wine
- Balance
- Consistency
- Style
- Complexity
- Minimise Faults
- Volume
- Price
Why might a winemaker blend with price in mind
especially inexpensive or mid-priced wines will be made to be sold profitable at a certain price point.
Blending different parcels can help to create a certain style/quality
e.g. Chardonnay is sometimes blended with varieties such as trebbiano or semicolon - grapes that are generally cheaper to buy.
Inclusion of Chardonnay - one of the most recognised varieties internationally - helps wine to sell
Conventional winemaking includes… (3)
Temperature Control
Use of additives and/or processing aids of many types
Manipulations
What is the main certifying association for biodynamic?
Demeter International
What affect does low levels of nitrogen have on yeast, and what can be added as a yeast nutrient?
Can stress the yeasts - causing them to produce undesirable sulphur compounds (rotten eggs) or stop fermenting
DAP or B1 can be added
Explain Fining
Fining agents can be of protein or mineral content
Fining agent must have opposite charge to the colloid to be removed - they bond to form a solid large enough to be removed by racking or filtration.
What are the 3 types of fining agent
Those that remove -
- unstable proteins
- phenolics that contribute undesirable colour and bitterness
- Colour and off-odours
Name and describe a fining agent used to remove unstable proteins
BENTONITE - form of clay, adsorbs unstable proteins and colloidal colouring matter - can have some colour loss in red wines
Causes a large amount of sediment so wine can be lost when racked off
Name and describe 6 fining agents used to remove phenolics that contribute undesirable colour and bitterness
EGG WHITE- not vegan. Removes harsh tannins and clarifies. Gentle
GELATINE - Not veg, not vegan. It is a protein collagen extracted from pork. Removes bitterness and astringency in red, browing in white
Easy to overfine - stripping flavour and character. Can be used on MUST or WINE. Risk of protein haze later
CASEIN - not vegan. Milk-derived protein. Removes browning from white wines. Can be used on MUST or WINE
VEG. PROTEIN PRODUCTS - potato/legume derived
ISINGLASS - not veggie not veg. Clarifies white wines - bright appearance. Derived from fish bladders.
Too much used = Risk of protein haze later, and possibility of fishy smell
PVPP - Insoluble plastic powder form - removes browning, astringency from oxidised white wine. Gentler than charcoal
Name and describe a fining agent used to remove colour and off-odours
CHARCOAL - Removes brown, off-odours
Over fines easily removing desirable aromas/flavours
One option is to treat only one batch of wine and blend with others to reduce the effect of the “fault”
Describe Depth filtration
Not an absolute filter. Like a sponge. If too much pressure is applied, it can allow some particles through
Most popular = Kieselguhr (Diamotaceous Earth)
Silica, intert - wetted and used as filter medium
Wine is sucked from outside rotary drum - it is an oxidative process, can be flushed with inert gas, High initial investment - can get in a range of particle sizes
Other are sheet filters. The more sheets, the quicker - any portion of wine only goes through one sheet
Initial investment, trained personnel
Describe Surface filtration
Membrane Filters - Wine must be pre-filtered. Used as final precaution before bottling
Can easily get blocked
Cross Flow filters - Continuous, cleans surface filter as it works. Expensive machines, for large and/or well-funded wineries
Describe Cold stabilisation, and what it is used for
Used for tartrate stability
Chill down to -4°C, 8 days, crystals form and can be filtered out. Colloids must be removed by fining prior, otherwise could prevent crystals forming.
Removes Potassium bitartrate, NOT calcium bitartrate. Equipment, energy costs
Describe contact process and what it is used for
Used for tartrate stability
Quicker, continuous, more reliable, cheaper form of cold stabilisation. Potassium bitartrate is added to the wine - speeds up crystallisation process. Wine is chilled to around 0°C. Takes 1-2 hours - then filter crystals out
Describe CMC and what it is used for
Tartrate stability
Cellulose extracted from wood, prevents tartrates developing to visible size. Used for inexpensive white/rose.
Not suitable for red as it reacts with tannins - becomes ineffective and causes a haze
Cheaper than chilling
Stability for a few years
Describe what metatartaric acid is used for and why
Prevents growth of potassium bitartrate and calcium bitartrate crystals , reducing need for cold stabilisation
Unstable compound - positive effect lost over time especially at storage of 25-30°C
Only suitable for early consumption wines
More for red (white or rose - cmc is the better option)
What do you do for protein stability?
Fine with bentonite
