Free Flashcards DipWSET D1: Wine Production – 8/Maturation

Describe the micro-oxygenation technique

• Increasing oxygen levels in wine can provide a more favorable environment for spoilage microbes (e.g. acetic acid bacteria and Brettanomyces)

The temperature and length of heat exposure at which the oak staves are exposed

[q] Generally, the longer a wine is aged in a wooden vessel the greater:

[a]

1. The extraction of compounds from the wood;
2. The exposure to oxygen

[q]

On what factors does the level of wood extraction depend?

[a]

• Type/source and age of wood
• Size of the barrel
• Toast level of the barrel
• Length of time in barrel
• Environment in the cellar

[q]

What alternatives to barrels exist for winemakers?

[a]  

• Oak chips
• Oak staves

[q]

Lees is a term for the sediment that settles on the bottom of a wine vessel.

What is that sediment made up of?

[a]

• Dead & dying yeast
• Bacteria
• Grape fragments
• Precipitated tannins
• Nutrients
• Other insoluble compounds

[q]

What are the gross lees?

[a]

The sediment that forms right after the end of fermentation (within the first 24 hours).

They are larger, heavier particles

[q] How are lees removed?

[a]

By racking

[q] The first racking after fermentation removes the ___ lees, and then subsequent periodic racking helps to manage the levels of ___ lees

[a]

First racking removes gross lees

Subsequent rackings remove fine lees

[q] What is the name of the process when yeasts die and break down, releasing compounds that contribute flavor, body and texture to the wine?

[a] Autolysis

[q]

What are some of the other compounds that autolytic compounds combine with?

How do those combinations affect the wine?

[a]

1. Phenolic compounds in the grapes
   • reducing color and softening tannins;
2. Wood tannins and wood flavors
   • ​​reducing astringency and modifying wood flavors

[q] What happens if the gross lees layer is too thick and not controlled?

[a]

• Volatile, reductive sulfur compounds can be produced (e.g. hydrogen sulphide {rotten egg smell});
• Can encourage the development of spoilage microbes (e.g. Brettanomyces)

[q] What are two benefits of lees aging?

[a]

• Stabilization of the wine against unstable proteins that can cause hazes later on;
• Protects the wine from oxygen;
  • slow, controlled oxidation during maturation reduces the need for SO₂

[q] What is bâtonnage?

[a]

Stirring of the lees

[q] What is racking, and what is its aim?

[a]

Transferring wine from one vessel to another with the aim of removing sediment from the wine.

This sediment may be gross lees, fine lees or other solid material in the wine that has fallen to the bottom of the vessel, such as tiny fragments of grape skin or tartrate crystals

[q]

Racking can be either oxidative or reductive

Explain how

[a]

When done oxidatively, winemakers will increase oxygen exposure by deliberately splashing the wine without any inert gas involved; good for red wines.

When done reductively, inert gas will flush the hose first and then push the wine through that same hose; good for aromatic or fruity white wines

[q] When is blending typically carried out?

[a]

Just before finishing and packaging

[q]

When winemakers blend wine, what exactly can be blended?

[a]

• Different grape varieties;
• Grapes from different locations (different vineyards, different regions or even different countries);
• Different vintages;
• Grapes that have had different treatment in the winery (e.g. wine fermented in stainless steel blended with wine fermented in new oak);
• Grapes that have been treated equally in the winery but are in different vessels for logistical reasons

[q]

What are the main reasons for blending wines?

[a]

• Balance
• Consistency
• Complexity
• Style
• Minimize faults
• Volume
• Price

[q]

What does the term “finishing” a wine mean?

[a]

Preparing it for its final packaging, which can include:

• clarifying;
• stabilizing;
• correcting SO_2;
• bottling

[q]

How far ahead of bottling is the final wine assembled?

[a]

8 weeks to 4 months

[q]

How far ahread of bottling are final adjustments made to a wine?

[a]

8 weeks

[q]

How far ahead of bottling are protein stability and tartrate stability checked and treated, if necessary?

[a]

4 weeks

[q] How far ahead of bottling are sweetening agents added to a wine

[a]

1-2 weeks

[q] How far ahead of bottling is free SO₂ adjusted, if necessary?

[a]

24 hours

[q] Name four processes used to clarify wine.

[a]

1. Sedimentation;
2. Centrifugation;
3. Fining;
4. Filtering

[q]

What is the most common way of clarifying wine?

[a]

Filtration

[q] Describe the sedimentation process

[a]

Clarification naturally begins when wine is stored in cool cellar conditions.

The wine is allowed to stand and particles (with higher density than wine) will form a sediment at the bottom of the container over time. The wine can then be racked off, leaving the sediment behind

[q]

The sedimentation process is most suitable for what price point of wine?

• Inexpensive to moderate priced
• Moderate priced
• Premium or super-premium priced

[a]

[q]   Describe the centrifugation process

[a]

Wine is spun at a high rotational speed causing matter in suspension to be separated out, thereby clarifying it. It is most effective with wines with a lot of matter in suspension.

[q] Which kind of winery uses centrifugation?

[a]

Only used in high-volume wineries to spread the considerable cost of buying the machine

[q] What is the purpose of fining?

[a]

To accelerate the process of precipitating suspended materials out of a wine

[q] What are fining agents made from?

[a]

Proteins or minerals

[q] What does fining do to a wine?

[a]

[q] What does fining remove from a wine?

[a]

1. Unstable colloids (microscopic particles) that are too tiny to be removed by filtration;
2. Harsh tannins in red wines;
3. Browning in white wines

[q]

A fining agent must have the:

• same charge
• opposite charge

of the colloid to be removed

[a]

Opposite charge

[q]

What are three categories of common fining agents?

[a]

Those that remove:

1. Unstable proteins;
2. Phenolics that cause unwanted color and bitterness;
3. Color and off-odors

[q]

Bentonite:

1. What is it made of?
2. What does it do?
3. What are the effects of using it?

[a]

1. A form of clay which has a strong negative charge;
2. Absorbs unstable proteins and unstable colloidal coloring particles;
3. Effects:
   • some color loss if used in red wines;
   • produces large amounts of sediment, so wine can be lost when it is racked off.
   • Minimal effect on the flavor and texture of wine

[q]

Bentonite can be used to

[a]

Fine must as well as wine

[q] Why isn’t bentonite suitable for removing tannins or bitter phenolics?

[a]

[q]

What colors of wine are most often fined with bentonite?

Why?

[a]

White and rosé wines

• proteins stick together and give these wines an undesirable haze, especially if the wine warms in transit

[q] Name 6 fining agents that remove phenolics that cause unwanted color and bitterness

[a]

1. Egg Whites;
2. Gelatin;
3. Casein;
4. Isinglass;
5. Vegetable proteins;
6. PVPP

[q]

Egg whites:

1. In what form are they used?
2. Used mostly for what style of wine?
3. Are they harsh or gentle on the wine?
4. Why are they problematic?

[a]

1. Fresh or powdered form;
2. Used for high-quality reds because of their ability to remove harsh tannins and clarify;
3. Gentle to the wine;
4. They are an allergen, and must be declared on the label if the wine is sold in the EU and other territories if above a specified limit

[q]

What is gelatin and from what is it derived?

1. What does it do?
2. What does it remove?
3. Is it vegetarian?

[a]

It’s a protein extracted from pig skins and animal bones by boiling.

1. Helps clarify wine;
2. Removes bitterness + astringency in reds and browning in whites, but may strip the wine of color and flavor so use minimum effective amount;
3. Not vegetarian

[q]

Gelatin can be used to:

• Fine must only
• Fine wine only
• Fine must as well as wine

[a]

Fine must as well as wine

[q]

Casein:

1. What is it?
2. What does it remove?
3. What’s problematic about it?

[a]

1. Milk-derived protein;
2. Removes browning from white wines + somewhat clarifies wines;
3. It’s an allergen, so must be on the label in some territories

[q]

Casein can be used to

[a]

Fine must as well as wine

[q]

Isinglass:

1. What is it?
2. What color wine is it mostly used on and why?
3. What makes it problematic?
4. Is it suitable for vegetarians?

[a]

1. A protein collagen derived from fish bladders. It comes in sheets, strips, chips, or coarse powder;
2. Mostly used in white wines to improve brightness and clarity;
3. If too much is used, wine can smell fishy and it can produce fluffy lees which clog filters and create haze;
4. Not suitable for vegetarians

[q]

Vegetable proteins:

1. From what are they derived?
2. Useful for what kind of wine?

[a]

• Derived from potatoes or legumes;
• Useful for vegan and vegetarian wines

[q]

PVPP (Polyvinylpolypyrrolidone):

1. What is it?
2. What does it remove?
3. What can it reduce or improve in red wines?

[a]

1. Insoluble plastic, used in powder form;
2. Removes browning + astringency from oxidized white wines;
3. Rarely used on red wines, but can reduce astringency + brighten color.

[q]

Name a fining agent that removes color and off-odors

[a]

Charcoal

Note!: Charcoal over-fines easily and can remove desirable aromas and flavors in addition to color and off-odors, so careful use is paramount.

One approach is to treat a small batch of the affected wine and then blend it with the rest of the wine

[q]

Describe filtration

[a]

It is a technique used to physically remove solids suspended in wine by passing the wine through a filter that has porous layers that trap the solid particles, thereby clarifying the wine

[q]

What are the two main types of filtration?

[a]

1. Depth filtration
2. Surface filtration

[q]

[a]

Wine that is heavy in particulates is passed through a thick filter with lots of irregular channels, and particles are trapped in the depth of the material that forms the filter.

Depth filters do not clog easily, but if too much wine is forced through it for too long the filter will pass some particles (it is not an absolute filter)

[q] What are the two types of filters used in depth filtration?

[a]

1. Diatomaceous earth filters;
2. Sheet filters

[q]

The most common form of depth filtration is by using ____.

What is it made of?

[a]

Diatomaceous earth

Diatomaceous earth (aka Kieselguhr, DE) is derived from a sedimentary rock composed of the skeletons of diatoms (microscopic algae) that lived 60-100 million years ago.

Once it has been processed, it is pure silica and inert

[q]

Which two filters use DE?

Are they oxidative or reductive processes?

[a]

Rotary vacuum filters use DE to filter very thick, cloudy wine (e.g. wine with lees). This is an oxidative process as the drum is exposed to air;
Enclosed DE filters do the same thing, but can be flushed with an inert gas (nitrogen) to avoid oxidation (reductive)

[q] Sheet filters are also known as “___ and ___” or “___” filters

[a] “Plate and frame” or “pad” filters

[q]

1. How do sheet filters work?
2. Are they cheap or expensive?

[a]

1. Wine is passed through a sheet of the filtering material;
   • The more sheets in the filter, the faster the wine is filtered because any portion of wine only passes through one sheet;
   • Sheets of very fine grade can be used to remove remaining yeasts at bottling;
2. It’s expensive to initially install them, but the sheets are affordable

[q] Describe surface filtration

[a]

Surface filters trap particulates larger than the pore size of the filter being used.

The pore sizes used in surface filtration tend to be smaller than the pore sizes used in depth filtration (often less than 1 micron), so they generally perform more slowly than using a depth filter

[q]

Surface filters are also termed ___ filters.

What do they do?

[a]

Absolute filters

Surface filters catch particles bigger than the filter’s pore size

[q] What are the two types of surface filters?

[a]

1. Membrane filters
2. Cross-flow filters

[q]

Membrane filters are a very common form of filtration during the ___ process.

Why?

[a]

Bottling/packaging process

• they are used as a final precaution right before bottling to ensure the wine is thoroughly clear and microbiologically stable (yeast and bacteria completely removed)

[q]

Membrane filters are also known as ___ filters

[a]

Cartridge filters

[q]

Cross-flow filters, aka tangential filters:

1. What are they best used for?
2. What’s unique about them?
3. Are they cheap or expensive?

[a]

1. Best for quickly filtering wine with lots of particles or lees;
   • solid particles cannot pass through them;
2. As wine passes through the filter it also cleans the surface of the filter;
3. Expensive, so best for large or well-funded wineries

[q]

Because membrane filters – one type of surface filter – have such tiny pores (< 1 micron), what do you have to do prior to using them?

[a]

Pre-filter the wine to remove heavy solids first, usually by depth filtration, otherwise the membrane filters will clog quickly

[q] As an umbrella term in winemaking, what is stabilization designed to do?

[a]

To stop a wine from developing faults in bottle, e.g. haziness, clouds, bubbles, browning, or deposits.

If wines are not stabilized, the finished wine risks having undesirable effects

[q]

What are three main areas in which winemakers want stability in their wines?

[a]

Protein stability;
Tartrate stability;
Microbiological stability

[q] What are tartrates?

[a]

Harmless crystals that precipitate out of a finished wine, principally made of potassium bitartrate and, less frequently, calcium tartrate.

They look like tiny, clear, glass-like crystals

[q]

What are the six methods used to prevent tartrate crystals from forming?

[a]

Cold stabilization;
Contact process;
Electrodialysis;
Ion exchange;
Carboxymethylcellulose (CMC);
Metatartaric acid

[q] To cold stabilize a wine, the wine must be held at what temperature and for how long?

[a]

-4°C (25°F) for ~8 days

This is so that tartrate crystals form and can be filtered out before bottling.

[q] If a winemaker is going to cold stabilize their wine, what step must they perform prior to cold stabilization, and why?

[a]

Wines must be fined prior to cold stabilization so that colloids can be removed – because colloids can prevent tartrate crystals from forming

[q]

Which tartrate crystal precipitates out during cold stabilization?

Potassium bitartrate
Calcium tartrate

[a]

Potassium bitartrate

[q]

What is the contact process in regards to tartrate stability?

[a]

Wine is seeded with finely powdered potassium bitartrate crystals which act as nuclei for further crystal growth, and the wine is then chilled to 0°C (32°F).

Contact process is less expensive than cold stabilization and faster (usually 1-2 hours); the wine will be stable at the temperature down to that at which it was treated

[q] Describe the electrodialysis process

[a]

This process is used for tartrate stabilization (mostly in the EU). It uses a charged membrane to remove selected potassium and calcium ions and, to a smaller extent, tartrate ions.

After costly initial investment, the total costs are lower than cold stabilization, plus it uses less energy and it’s faster.

[q]

Describe the ion exchange process

[a]

This process is used for tartrate stability, but it does not remove tartrates; instead, it replaces potassium and calcium ions with hydrogen or sodium ions, which will not precipitate out of the solution.

This process isn’t permitted in some territories because it replaces the potassium with sodium which is seen as unhealthy, even though the resulting sodium levels in the wine are well below the legal limit

[q] Describe carboxymethylcellulose (CMC) use when performing tartrate stabilization

[a]

CMC is cellulose that is extracted from wood and prevents tartrates from developing to a visible size.

CMC is widely used on cheap white and rosé wines, and it is not suitable for red wines because it reacts with tannins and causes haze.

It is much less expensive than chilling, and CMC keeps wines stable for a few years

[q] Describe the use of metatartaric acid during tartrate stabilization

[a]

This compound prevents the growth of potassium bitartrate and calcium tartrate crystals, reducing the need for cold stabilization.

However, the compound is unstable. Its positive effect is lost over time, especially when wine is stored at high temperatures (25–30°C / 77–86°F).

It is a quick and easy process that tends to be used more for red wines (white and rosé wines in the same category will use CMC instead as it is more effective and longer lasting)

[q]

When a winemaker performs microbiological stabilization on a wine, what are they removing from the wine?

[a]

Yeasts and bacteria, which, if left in the wine, could potentially restart fermentation in the bottle

[q] Wines that have residual ____ are more at risk of starting to referment in the bottle

[a]

Sugar

[q]

What are the two ways in which wines may be treated for microbiological stabilization?

[a]

They go through sterile filtration, thereby removing all yeasts;
Adding sorbic acid and SO2, which inhibit yeast from growing

[q]

Name two microbes that can live in wine (read: in an environment that’s low in pH with high alcohol levels)

[a]

Lactic acid bacteria

Brettanomyces (a spoilage yeast)

[q]

If malolactic conversion wasn’t completed or if a wine wasn’t filtered to remove lactic acid bacteria, what can potentially happen to the finished wine?

[a]

Malolactic conversion can start up again in the bottle, causing cloudiness in the wine

[q]

[a]

The winemaker can try filtering first to see if that helps;
Treat with DMDC (dimethyl dicarbonate, commercial name: Velcorin) before bottling, which inactivates Brettanomyces

[q]

Winemakers will perform a full chemical analysis on their wine prior to employing any final finishing options prior to bottling.

What are the major things winemakers are analyzing?

[a]

Alcohol;
Residual sugar;
Total SO2;
Free SO2;
Dissolved oxygen;
Dissolved CO2

[q] What are the general ranges of free SO2 in white, red, and sweet wines?

[a]

• White wines: 25–45 mg/l
• Red wines: 30–55 mg/l
• Sweet wines: 30–60 mg/l

[q] What can a winemaker do if they find the level of dissolved oxygen in their wine is too high?

[a]

The winemaker can flush the wine with an inert gas to remove the oxygen, a process called sparging

[x] GOOD JOB!! [restart]

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