D1 Maturation 1: Oxygen, Wood, Lees; Blending, Finishing, Stabilization Flashcards
Winemaking options which help determine style and quality of a wine. (109 cards)
1
Q
What are three key factors that can influence wine during maturation?
A
- Oxygen;
- New wood;
- Lees.
2
Q
How does oxygen influence wine aromas during maturation?
A
- Reduces many primary aromas;
- Helps develop tertiary aromas.
3
Q
How does oxygen affect the color of white and red wines?
A
When exposed to oxygen, white wines become darker (gold, then brown);
When exposed to oxygen, red wines become lighter (paler, then brown).
4
Q
Which of the following is the speed of oxidation directly related to?
- The color of the wine
- The style of the wine
- The amount of oxygen exposure, the compounds in the wine, and temperature
A
The amount of oxygen exposure, the compounds in the wine, and temperature.
A wine that sees more gradual oxygen exposure will oxidize less quickly than a wine that is fully exposed to air.
5
Q
Why can red wines often mature longer than white wines?
A
Red wines can take a higher level of oxygen exposure than white wines due to their higher content of anti-oxidative phenolic compounds (such as tannins).
6
Q
How is wine exposed to oxygen when it is being matured in wooden barrels?
A
- Oxygen passes through the gaps between the staves and the bung hole;
- Some oxygen is released from the pores in the barrel within the first month that the vessel is filled with wine;
- During racking, lees stirring, and topping up.
7
Q
Why does topping up in small barrels lead to more oxygen exposure than in larger barrels?
A
Because small barrels have a large surface area-to-volume ratio, water and alcohol evaporate more quickly which forces their need to be topped up more frequently to keep them full, with oxygen entering the barrel every time the bung is removed.
8
Q
The micro-oxygenation technique: what is it, and when is it carried out?
A
- It’s a cheaper way to oxygenate wine by forcing oxygen bubbles through the wine;
- It is generally carried out in stainless steel tanks over several months after alcoholic fermentation.
Wines at every price point can practice micro-oxygenation.
9
Q
What are the advantages of micro-oxygenation?
A
- Increases color stability and intensity;
- Softens tannins and improves texture;
- Reduces unripe, herbaceous flavors;
- Provides gentle exposure to oxygen more quickly than barrel aging (don’t need expensive barrels, reducing costs);
- Control rate of oxygen exposure better than in a barrel;
- If used with oak alternatives (e.g. chips or staves), can help integrate the influence of oak flavors.
10
Q
What is a big potential disadvantage of micro-oxygenation?
A
Increasing oxygen levels in wine can provide a more favorable environment for spoilage microbes (e.g. acetic acid bacteria and Brettanomyces).
11
Q
Why are wines usually matured in cool cellars with constant temperature and humidity?
A
- Slows down the rate of oxidation;
- Slows down chemical reactions;
- Lowers the chance of microbial spoilage;
- Provides slower maturation process;
- Slows the rate of wine loss;
- Higher humidity means less evaporation (and slower alcohol concentration).
12
Q
A new oak barrel loses about ___% of its new oak flavors during the first year of use.
A
50%
13
Q
Oak barrels will impart little to no oak flavor at all by their ___ year of use.
A
4th
It will still allow ingress of oxygen, though.
14
Q
How many liters do barriques hold?
A
225 L
This means that any extraction from the wood and exposure to oxygen is greater in barriques than in foudres.
15
Q
What are three positive attributes of oak barrels?
A
- Easily shaped;
- Makes watertight containers;
- Has significant levels of vanillin (imparts vanilla aromas in wine).
16
Q
What is the key difference between American oak and European oak?
A
American oak has higher level of lactones (which impart coconut aromas)
17
Q
European oak tends to impart more ____ than American oak.
A
Tannin
18
Q
Which oak grows faster: American or European oak trees?
A
American
19
Q
To make staves, American oak can be ___ whilst European oak must be ____.
A
American oak = sawn
European oak = split (more expensive)
20
Q
- The slower the growth of oak trees, the ____er the grain.
- The tighter the grain, the ____er the extraction of oak compounds.
A
- Tighter
- Slower
21
Q
What three things happen to wood during its ‘seasoning’ stage?
How long does seasoning take and where does it take place?
A
- Reduction in humidity levels in the wood;
- Reduction in bitter flavors;
- Increase of some aroma compounds.
Takes place outside and lasts 2-3 years
22
Q
What are the toasting categories for oak?
A
- Light toast;
- Medium toast;
- Heavy toast.
23
Q
What flavor characteristics does toasted oak contribute to wine?
A
- Spice;
- Caramel;
- Roasted nuts;
- Char;
- Smoke.
These notes become more pronounced at heavy levels of toasting.
24
Q
What exactly is ‘toasting’?
A
The temperature and length of heat exposure at which the oak staves are exposed.
25
Generally, the longer a wine is aged in a wooden vessel the greater:
1. The **extraction** **of compounds** from the wood;
2. The **exposure to oxygen**.
26
On what factors does the level of wood extraction depend?
* Type/source and age of wood;
* Size of the barrel;
* Toast level of the barrel;
* Length of time in barrel;
* Environment in the cellar.
27
What alternatives to barrels exist for winemakers?
* Oak chips
* Oak staves
28
Lees is a term for the sediment that settles on the bottom of a wine vessel.
What is that sediment made up of?
* Dead & dying yeast;
* Bacteria;
* Grape fragments;
* Precipitated tannins;
* Nutrients;
* Other insoluble compounds.
29
What are the gross lees?
The sediment that forms right after the end of fermentation (within the first 24 hours).
They are larger, heavier particles.
30
How are lees removed?
By racking
31
The first racking after fermentation removes the ___ lees, and then subsequent periodic racking helps to manage the levels of ___ lees.
First racking removes **gross** lees;
Subsequent rackings remove **fine** lees.
32
What is the name of the process when yeasts die and break down, releasing compounds that contribute flavor, body and texture to the wine?
Autolysis
33
What are some of the other compounds that autolytic compounds combine with?
How do those combinations affect the wine?
1. **Phenolic compounds** in the grapes
* reducing color and softening tannins;
2. **Wood tannins and wood flavors**
* ****reducing astringency and modifying wood flavors.
34
What happens if the gross lees layer is too thick and not controlled?
* Volatile, reductive sulfur compounds can be produced (e.g. hydrogen sulphide {rotten egg smell});
* Can encourage the development of spoilage microbes (e.g. Brettanomyces).
35
What are two protective benefits of lees aging?
* **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.
36
What is bâtonnage?
Stirring of the lees
37
What is racking, and what is its aim?
**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.
38
Racking can be either oxidative or reductive.
Explain how.
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.
39
When is blending typically carried out?
Just before finishing and packaging
40
When winemakers blend wine, what exactly can be blended?
1. Different grape varieties;
2. Grapes from different locations (different vineyards, different regions or even different countries);
3. Different vintages;
4. Grapes that have had different treatment in the winery (e.g. wine fermented in stainless steel blended with wine fermented in new oak);
5. Grapes that have been treated equally in the winery but are in different vessels for logistical reasons.
## Footnote
*All of this depends on the wine's PDO, regulations, and laws around what can and cannot be blended.*
41
What are the main reasons for blending wines?
* Balance;
* Consistency;
* Complexity;
* Style;
* Minimize faults;
* Volume;
* Price.
42
What does the term "finishing" a wine mean?
Preparing it for its final packaging, which can include:
* clarifying;
* stabilizing;
* correcting SO2;
* bottling.
43
How far ahead of bottling is the final wine assembled?
8 weeks to 4 months
44
How far ahead of bottling are final adjustments made to a wine?
8 weeks
45
How far ahead of bottling are protein stability and tartrate stability checked and treated, if necessary?
4 weeks
46
How far ahead of bottling are sweetening agents added to a wine?
1-2 weeks
47
How far ahead of bottling is free SO2 adjusted, if necessary?
24 hours
48
Name four processes used to clarify wine.
1. Sedimentation;
2. Centrifugation;
3. Fining;
4. Filtering.
49
What is the most common way of clarifying wine?
Filtration
50
Describe the sedimentation process.
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.
## Footnote
*The bigger the vessel, the more rackings needed so as to avoid a super thick layer of sediment.*
51
The sedimentation process is most suitable for what price point of wine?
* Inexpensive to moderate priced
* Moderate priced
* Premium or super-premium priced
Premium or super-premium priced
## Footnote
*Sedimentation takes time to carry out, and this has a cost to the winemakers as the wine cannot be sold until it is ready.*
52
Describe the centrifugation process.
Do small, medium, or high-volume wineries use this process?
**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.
Only used in **high-volume wineries** to spread the considerable cost of buying the machine.
53
What is the purpose of fining?
To accelerate the process of precipitating suspended materials out of a wine.
54
What are fining agents made from?
Proteins or minerals
55
What does fining do to a wine?
**Helps clarify and stabilize** the wine; if fining isn't employed, the wine could later become hazy in the bottle
56
What does fining remove from a wine?
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.
57
A fining agent must have the:
* same charge
* opposite charge
of the colloid to be removed.
Opposite charge
58
What are three categories of common fining agents?
Those that remove:
1. Unstable proteins;
2. Phenolics that cause unwanted color and bitterness;
3. Color and off-odors.
59
Bentonite:
1. What is it made of?
2. What does it do?
3. What are the effects of using it?
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;
60
Bentonite can be used to:
* Fine must only
* Fine wine only
* Fine must as well as wine
Fine must as well as wine
61
Why isn't bentonite suitable for removing tannins or bitter phenolics?
Because **bentonite has the same charge as tannins;** and if they're the same charge, they won't be attracted to one another.
62
What colors of wine are most often fined with bentonite?
Why?
**White and rosé** wines
* proteins stick together and give these wines an undesirable haze, especially if the wine warms in transit
## Footnote
*In red wines, these proteins bind with tannins and are removed when the wine is racked.*
63
Name 6 fining agents that remove phenolics that cause unwanted color and bitterness.
1. Egg Whites;
2. Gelatin;
3. Casein;
4. Isinglass;
5. Vegetable proteins;
6. PVPP.
64
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?
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.
65
What is gelatin and from what is it derived?
1. What does it do?
2. What does it remove?
3. Is it vegetarian?
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**.
66
Gelatin can be used to:
* Fine must only
* Fine wine only
* Fine must as well as wine
Fine must as well as wine
67
Casein:
1. What is it?
2. What does it remove?
3. What's problematic about it?
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.
68
Casein can be used to:
* Fine must only
* Fine wine only
* Fine must as well as wine
Fine must as well as wine
69
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?
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**.
70
Vegetable proteins:
1. From what are they derived?
2. Useful for what kind of wine?
1. Derived from **potatoes or legumes**;
2. Useful for **vegan and vegetarian wines**.
71
PVPP (Polyvinylpolypyrrolidone):
1. What is it?
2. What does it remove?
3. What can it reduce or improve in red wines?
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**.
72
Name a fining agent that removes color and off-odors.
**Charcoal**
## Footnote
*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.*
73
Describe filtration.
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.
74
What are the two main types of filtration?
1. **Depth** filtration;
2. **Surface** filtration.
75
Describe depth filtration.
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).
76
What are the two types of filters used in depth filtration?
1. **Diatomaceous earth** filters;
2. **Sheet** filters.
77
The most common form of depth filtration is by using \_\_\_\_.
What is it made of?
**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**.
78
Which two filters use DE?
Are they oxidative or reductive processes?
1. **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;
2. **Enclosed DE filters** do the same thing, but can be flushed with an inert gas (nitrogen) to **avoid oxidation (reductive)**.
79
Sheet filters are also known as "\_\_\_ and \_\_\_" or "\_\_\_" filters.
"**Plate and frame**" or "**pad**" filters
80
1. How do sheet filters work?
2. Are they cheap or expensive?
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**.
81
Describe surface filtration.
**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.
82
Surface filters are also termed ___ filters.
What do they do?
**Absolute** filters
Surface filters **catch particles** **bigger than the filter's pore size**.
83
What are the two types of surface filters?
1. **Membrane** filters
2. **Cross-flow** filters
84
Membrane filters are a very common form of filtration during the ___ process.
Why?
**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).
85
Membrane filters are also known as ___ filters.
Cartridge filters
86
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?
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.
87
Because membrane filters -- one type of surface filter -- have such tiny pores (\< 1 micron), what do you have to do prior to using them?
**Pre-filter the wine to remove heavy solids first**, usually by depth filtration, otherwise the membrane filters will clog quickly.
88
As an umbrella term in winemaking, what is stabilization designed to do?
**To stop a wine from developing faults in bottle**, e.g. haziness, clouds, bubbles, browning, or deposits.
## Footnote
If wines are not stabilized, the finished wine risks having undesirable effects.
89
What are three main areas in which winemakers want stability in their wines?
1. **Protein** stability;
2. **Tartrate** stability;
3. **Microbiological** stability.
90
What are tartrates?
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.
91
What are the six methods used to prevent tartrate crystals from forming?
1. Cold stabilization;
2. Contact process;
3. Electrodialysis;
4. Ion exchange;
5. Carboxymethylcellulose (CMC);
6. Metatartaric acid.
92
To cold stabilize a wine, the wine must be held at what temperature and for how long?
-4°C (25°F) for ~8 days
## Footnote
This is so that tartrate crystals form and can be filtered out _before_ bottling.
93
If a winemaker is going to cold stabilize their wine, what step must they perform _prior_ to cold stabilization, and why?
**Wines must be fined** prior to cold stabilization so that colloids can be removed -- because colloids can prevent tartrate crystals from forming.
94
Which tartrate crystal precipitates out during cold stabilization?
* Potassium bitartrate
* Calcium tartrate
Potassium bitartrate
95
What is the contact process in regards to tartrate stability?
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.
96
Describe the electrodialysis process.
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.
97
Describe the ion exchange process.
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.
98
Describe carboxymethylcellulose (CMC) use when performing tartrate stabilization.
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.
99
Describe the use of metatartaric acid during tartrate stabilization.
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).
100
When a winemaker performs microbiological stabilization on a wine, what are they removing from the wine?
Yeasts and bacteria, which, if left in the wine, could potentially restart fermentation in the bottle.
101
Wines that have residual \_\_\_\_ are more at risk of starting to referment in the bottle.
Sugar
102
What are the two ways in which wines may be treated for microbiological stabilization?
1. They go through **sterile filtration**, thereby removing all yeasts;
2. **Adding sorbic acid and SO2**, which inhibit yeast from growing.
103
Name two microbes that can live in wine (read: in an environment that's low in pH with high alcohol levels).
1. Lactic acid bacteria;
2. Brettanomyces (a spoilage yeast).
104
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?
Malolactic conversion can start up again in the bottle, causing cloudiness in the wine.
105
How is wine treated for Brettanomyces?
* The winemaker can try filtering first to see if that helps;
* Treat with DMDC (dimethyl dicarbonate, commercial name: Velcorin) before bottling, which inactivates Brettanomyces.
106
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?
* Alcohol;
* Residual sugar;
* Total SO2;
* Free SO2;
* Dissolved oxygen;
* Dissolved CO2.
107
What are the general ranges of free SO2 in white, red, and sweet wines?
* White wines: 25–45 mg/l
* Red wines: 30–55 mg/l
* Sweet wines: 30–60 mg/l
108
What can a winemaker do if they find the level of dissolved oxygen in their wine is too high?
The winemaker can flush the wine with an inert gas to remove the oxygen, a process called **sparging**.
109
Blending red and white wines to make rosé is not allowed in many geographical indications within the EU **except for these 2 regions**:
1. Champagne;
2. Franciacorta.
