Winemaking Flashcards
What are Anti-oxidative Phenolic Compounds
Compounds found in red wine that slow oxidation
(Phenolic compounds in red wines have an anti-oxidative effect, which means that they can absorb more oxygen before oxidation effects are perceptible)
How long does wine generally spend in pre bottling maturation (red and white)
White wine - 6-12 months
Red wine - 12-24 monthss
What is Ullage
Headspace within a container that allows the wine to come in contact with oxygen.
Can be filled with inert gas (nitrogen, carbon dioxide, argon) to prevent/slow oxidation.
How does wine get oxygen exposure during maturation
Racking,
Lees stirring,
Topping up.
Whenever the bung is removed.
What are the effects of Micro-oxygenation
- Colour stability and intensity
- Soften tannins
- Improve texture
- Herbaceous flavours (lessen)
- Oxygen exposure. Gentle controlled, quick and cheaper than barrel aging.
Integrate any oak alternatives used (chips, staves).
Lactones
Compounds that give American oak the aromas of coconut.
What and how - Reduction (fault)
Rotten egg smell that comes from high levels of hydrogen sulphide.
Fault from uncontrolled/unmonitored ageing on gross lees.
Bottling without sufficient oxygen or ingress via closure.
What might differ about wines that are blended together
- grape varieties
- locations (from different vineyards, different regions or even different countries)
- grape growers or businesses that sell grapes, must or wine
- vintages
- treated differently in the winery (e.g. wine made from free run juice and wine made from press juice, or wine matured in oak with wine that has been stored in stainless steel or concrete)
- equally in the winery but are in different vessels for logistical reasons (e.g. unless a wine is made in very small quantities, wine fermented or matured in barrels will need to be blended together to make up the required volume).
Key reasons for blending wines
Balance – Blending may help to increase or moderate the levels of certain characteristics of the wine to produce a wine that is better balanced, and in this way enhance quality. (Merlot in Bordeaux provides body and ripe, plummy fruit to a blend with Cabernet Sauvignon, which can be too astringently tannic if not fully ripe)
Consistency – Across vintage or many years depending on wine style (Sherry and non-vintage sparkling wine, inexpensive wines).
Style – ‘house style’ or required style (rose)
Complexity – The blending of two or more parcels of wine may lead to a greater range of flavours.
Minimise faults – If wine in one barrel is showing significant volatile acidity (see Faults), that wine may be sterile-filtered to remove acetic acid bacteria and then blended into a larger volume of un-faulty wine. Lower concentration and sensory perception of Acetic Acid.
Volume – Blend the wines from different small vineyards to produce viable volumes of certain wines, or in poor vintages where yields are low.
Price – Include cheaper grapes along with more well recognised expensive grapes - eg Chardonnay and Trebbiano.
Bottling day checklist
4 months to 8 weeks ahead - Assemble final blend
Full chemical analysis – alcohol, residual sugar, free SO2, etc.
8 weeks ahead - Final adjustments: alcohol, acidity, tannins if desired
6 weeks ahead - Protein stability trial and if necessary fine with bentonite
4–6 weeks ahead - Test for tartrate stability and, if necessary, treat - 4 weeks ahead
Check protein stability and tartrate stability again, treat as necessary
1–2 weeks ahead - Add sweetening agents e.g. grape concentrate, if using (for mouth feel and finish)
72–48 hour ahead - Test filterability of wine
24 hours ahead - Adjust free SO2
Bottling day - Adjust dissolved oxygen and CO2
During bottling - Check dissolved oxygen (to ensure no pickup) and SO2 levels regularly and keep sample of bottle wines for quality assurance purposes
Three categories of fining agents
- Remove unstable proteins
- Remove phenolics that contribute undesirable colour and bitterness
- Remove colour and off-odours.
What are tartrates
Harmless deposits of crystals that can form in the finished wine
potassium bitartrate
calcium tartrate (less common)
How to treat Brettanomyces in wine
Brettanomyces is a problem, wine can be treated with DMDC (dimethyl dicarbonate, commercial name: Velcorin)
What are the generally allowed amounts of SO2 before bottling
White wine: 25–45 mg/l (lower than for red wines due to lower pH)
Red wine: 30–55 mg/l
Sweet wine: 30–60 mg/l
What is sparging
Flushing wine with an inert gas to remove oxygen (done before bottling).
What causes cork taint and how does it affect the aroma/flavour of the wine
TCA (2,4,6-trichloroanisole).
- Unpleasant smell of mould or wet cardboard
- Suppresses the fruit character.
What is OTR
Oxygen transmission rate. Refers to how permeable wine bottle closure is.
What aromas do volatile reductive sulphur compounds give in wine
Low levels - aromas that may be perceived as positive, such as struck match and smoke.
High levels they give rotten egg (always a fault) and other unpleasant aromas.
What does HACCP stand for and mean
HACCP (Hazard Analysis of Critical Control Points):
Identify each hazard and what can go wrong. The state how serious the hazard is, how it can be prevented and how it can be corrected.
What is a Flexitank
A single-use, recyclable polyethylene bag that fills a standard container for bulk shipping of wine.
Purpose of skin contact in white wine production
- Extraction of aroma and flavour compounds and precursors.
- Improve texture of the wine by extracting a small amount of tannin.
Why would winemakers choose to press whole bunch, uncrushed grapes.
- Limit skin contact
- Reduce risk of oxidation
Typical for wines requiring: - Early drinking
- Delicate fruity flavours
- Minimal colour
- Smooth mouthfeel.
How are Orange Wines made and what is their flavour profile
Amber (orange) coloured wines that are fermented on their skins without temperature control or SO2 added. The colour develops due to the oxidation of compounds extracted from the grape skins.
Flavour profile:
- Dry
- Notable levels of tannins
- Mainly tertiary characteristics (nuts and dried fruit).
Define Free Run Juice and describe it’s characteristics
The juice that can be drained off the press as soon as the grapes are crushed.
(whole bunches, destemmed)
Characteristics:
Lowest levels of solids, tannin and colour of the
Highest acidity and sugar.
What are Press Fractions
Juice from different stages of pressing (free run is the first)
Different press fractions may be blended later in the winemaking and maturation process.
The last press fractions too generally astringent or bitter (due to phenolic compounds from the skins, seeds or stems) to use.
What esther gives a banana like smell
Isoamyl Acetate
What is the French term for lees stirring
Bâtonnage
What are the conditions for Noble Rot and how does it affect the grape.
- The grapes must be fully ripe.
- Humid, misty mornings followed by sunny, dry afternoons.
- Damp conditions in the morning allow rot to develop on the grapes.
- The fungus punctures the grape skin with microscopic filaments, leaving tiny holes in the skin.
- Warm sunny afternoons slow the rot and cause water to evaporate from the grape.
- Modifies aroma compounds in the grape adds flavours. Honey, apricot, citrus zest, ginger and dried fruit.
Define cryoextraction in terms of ice wine and advantages/disadvantages
Picking grapes as usual and then freezing them at a winery.
Advantages:
- Does not entail the risks of leaving the grapes on the vine into late autumn or winter.
- Lessens risk of yield loss to disease or pests.
- Much cheaper than traditional production.
Disadvantages:
- The terms Eiswein and Icewine cannot be used on the label.
- Energy to freeze the grapes.
How is fermentation interrupted
- Chilling to below 10°C (50°F)
- And/or add a high dose of SO2 to inhibit the yeast.
- Rack off its sediment and sterile filter to ensure fermentation does not start again
Which winemaking processes cause red wine to lose colour (anthocyanins)
- Lees aging
- Addition of SO2
What is pigeage
Punching down
What is remontage
Pumping over
What is delestage
Rack and return
What is saignée
Must concentration
What flavours does whole berry/bunch fermentation add to red wine
Kirsch, banana, bubble gum and cinnamon.
Kinds of depth filtration
Depth filtration: Not absolute. Use a porous filtration medium to retain particles throughout the medium, rather than just on the surface.
- Diatomaceous earth - traps particles in the material. Filters must or lees,
- Rotary vacuum filters. Oxidative
- Enclosed filters can be flushed with inert gas
- Comes in range of particle sizes large->small
- Must be disposed of responsibly once used.
- Sheet filters (yeast and bacteria) - ‘plate and frame’ / ‘pad’. Wine passed through sheet of material - more sheets = quicker filter. Fine sheets remove yeasts at bottling.
- Expensive initial investment
- Sheets are cheap.
- Trained labour
Kinds of surface filtration
Surface filtration: Absolute. Particles greater than the pore size of the filter on the filter surface
Membrane filters - Very small pores (<1 micron). Must be filtered by depth filtration first to prevent blockage. Final filtration before wine is bottled (filters out yeasts and bacteria - micro biologically stable)
Cross-flow (tangental) filters - wine passes through filter whilst cleaning the surface. Filter high load very quickly, no filter material to buy. Expensive (large + high value wines).
Why would a winemaker choose not to filter
Negatively affects wine’s character, strips it of it’s texture.
Argument against not filtering
- ‘Filtration shock’ - wine recovers after a few months.
- Correctly fined wine expresses fruit and terroir better.
What should wine be fined with to ensure protein stability
Bentonite
What are tartrates
Harmless crystal deposits that form in finished wine:
- Potassium bitartrate (common)
- Calcium tartrate (less common)
Many customers regard this as a fault.
What three kinds of stabilisation should a winemaker consider
- Protein stability
- Tartrate stability
- Microbiological stability
What is microbiological stability and how is this achieved
Lactic acid and Brettanomyces can live in the bottle and withstand ph and alcohol levels in wine.
Wines with residual sugar and wines that have not gone through complete malolactic conversion are particularly at risk.
Wines that have not had malo completed run the risk of it occuring in the bottle (a fault)
Treatments
- Sorbic acid - low levels can be detected by some people.
- SO2
- Sterile filtration (fine enough to remove yeast and bacteria)
Options for ensuring tartrate stability
Potassium bitartrate and Calcium tartrate
- Cold stabilisation - Held at -4C for 8 days so crystals form, then filtered out. Traditionally happens when wine is kept in cold cellar for months in winter. Colloids must be fined out first, removes PT not BT. Cost of refrigeration equipment and power.
- Contact process - Potassium bitartrate added to wine, seeds crystal formation. Cooled to 0c for 1-2 hours. Crystals filtered out. Quicker, more reliable and cheaper.
- Electrodialysis - Charged membrane to remove selected ions. High initial investment, total costs lower (less energy, faster).
- Ion exchange - Replaces potassium and calcium ions with hydrogen or sodium ions preventing them dropping out of wine. Not allowed in some places as sodium = bad.
- CMC (Carbomethylcellulose) - Extracted from wood. Prevents tartrates developing to visible size. Used on inexpensive red or rose but red wines = tannins = haze. Stability for a few years, much cheaper than chilling.
- Metatartaric acid - Prevents growth of crystals. Compound is unstable and loses effect over time and at high temperatures (25-30C). Quick and easy used for inexpensive red wines.
What can a wine maker do just before bottling (finishing)
- Adjust levels of SO2: Depends on ph level and intended drinking period.
- Reduce dissolved oxygen: Can accellerate aging speed and reduce shelf life. Removed by sparging.
- Add carbon dioxide: Added in for extra freshness (inexpensive fresh white + rose wine)
What are the normal levels of free SO2 in wine
- White - 24/45 mg/l
- Red - 30-55mg/l (lower PH requires less)
- Sweet - 30-60ml/l
List main wine faults (9)
- Cloudiness and hazes
- Tartrates - Most inexpensive + mid priced wines are stabilised but sometimes not successful.
- Bottle refermentation - cloudiness, bubbles or spritz. Failure to stabilise and clarify/filter.
- Cork taint - Mouldy, wet cardboard smell, reduces fruit and shortens wine finish.
- Oxidation - Faulty bottling, poor quality corks or closures, keeping wine for too long not ment for again. Brown in colour, no primary fruit, vinegar.
- Volatile Acidity (vinegar) - nail varnish / vinegar. Acetic acid bacteria, inadequate SO2, oxygen exposure. Avoided by excluding damanged grapes, hygiene in winery, avoiding ullage, careful racking, SO2.
- Reduction - volatile reductive sulfur compounds. Stuck match -> onion & rotten eggs.
- Light Strike - UV radiation / visible light. Florescent lighting, light coloured glass. Dirty drains. Volatile sulphur compounds.
- Brettanomyces - Animal, spicy, farmyard smells. Can add complexity at low level, fault at high level - off flavours dominate, fruit is reduiced and acidity / tannin becomes prominent.
How does Brettanomyces affect the wine and how should it be treated
Gives Animal, spicy, farmyard smells. Can add complexity at low level, fault at high level - off flavours dominate, fruit is reduiced and acidity / tannin becomes prominent.
Avoid by:
- excellent hygiene
- maintaining effective SO2 levels
- keep PH levels low
- keep period between fermentation and malo short so SO2 can be added ASAP.
Treat with:
- Velcorin (DMDC - dimethyl dicarbonate)
Main considerations when selecting wine packaging and closures
- Oxygen management
- Place in the market
- early sale
- aging + long life
- Markets in which it will be sold.
Effects of too much or too little oxygen when packaging wine
Too little:
- reductive sulphur compounds develop
Too much:
- premature browning + oxidised characteristics.
What is ‘total package oxygen’ in wine
- Oxygen dissolved in the wine
- Oxygen in head space (most)
- Oxygen transmission rate (OTR) of the closure.