Stabilization

Question 1

Define stabilization.

Answer 1

Refers to several winemaking techniques that prevent undesired effects in the finished wine, including unwanted hazes, deposits in the bottle, and rapid color change.

Question 2

Name three elements of stability that can be addressed with stabilization techniques.

Answer 2

• protein stability
• tartrate stability
• microbiological stability

Question 3

What can protein instability lead to?

Answer 3

• unwanted haze in wine

Question 4

What can tartrate instability lead to?

Answer 4

• tartrate crystals forming in the bottle

Question 5

What can microbiological instability lead to?

Answer 5

• fermentation in the bottle, leading to off flavors, faults, and carbonation

Question 6

Name tartrate stabilization techniques.

Answer 6

• cold stabilization
• contact process
• electrodialysis
• ion exhcnage
• carboxymethylcellulose (CMC)
• metatartaric acid

Question 7

How does cold stabilization of tartrates work? What are the disadvantages?

Answer 7

1. Wine is reduced to temps below OC, which forces potassium tartrate crystals out of the solution.
2. The crystals are then filtered out.
3. Colloids must be removed before chilling, otherwise a haze will form.

• cold stabilization costs money for the equipment and energy required
• it only removes potassium bitartrate, but not calcium tartrate

Question 8

How does the contact process remove tartrates?

Answer 8

• a more reliable and cheaper form of cold stabilization

1. Potassium bitartrate is added to the wine, which seeds the formation of crystals.
2. The wine is cooled to 0C, and after an hour or two, the new crystals are filtered out.

Question 9

How does electrodialysis work to improve tartrate stability?

Answer 9

Electrodialysis uses a charged membrane to remove selected ions.

• the equipment is expensive, but total costs are lower than cold stabilization, and uses less energy
• it is fast, and can remove both potassium and calcium ions
• it is permitted in the EU for tartrate stabilization

Question 10

How is ion exchange used for tartrate stabilization?

Answer 10

Ion exchange replaces potassium and calcium ions with hydrogen or sodium ions.

It is not permitted in some territories, as it can involve the addition of sodium.

Question 11

How is Carboxymethylcellulose, CMC, used for increasing tartrate stability?

Answer 11

CMC is a wood-derived product that prevents tartrates from developing to a visible size.

• it’s widely used for inexpensive white wines, but is not suitable for red wines because it reacts with tannins
• much cheaper than chilling, and can keep wine stable for a few years

Question 12

How is metatartaric acid used to improve tartrate stability?

Answer 12

Metatartaric acid prevents the growth of potassium bitartrate and calcium tartrate crystals.

• it’s an unstable compound, and can only be used for wines designed for early consumption
• its positive effect is lost if the wine is stored at high temperatures
• quick, easy, and mostly used for red wines

Question 13

How can microbiological stability be achieved?

Answer 13

• sterile filtration
• addition of sorbic acid and SO2
• dimethyl dicarbonate, for Brett