MAINTAINING TEMPERATURE STABILITY IN YOUR WINE

Have you ever noticed after finishing a bottle of wine that on occasion

there is a dark dusty-looking deposit clinging to the bottom of the bottle?

Have you ever had a wine become cloudy in the bottle after it was once

beautifully clear?

These are two examples of what can happen when a wine is unstable.

What is meant by "unstable" is simply, there are still changes that may

occur in the wine when the conditions are right.

There are many changes that occur during the production of a wine -

some organic, some chemical - some good, some bad. Some are obvious

such as a fermentation. Some are more subtle such as the enzymatic

changes that take place during the aging process.


- What Is Precipitation

One type of change that can occur in a wine that causes a lot of problems

for the unsuspecting winemaker is called precipitation. Precipitation is

when particles occur in a wine from out of nowhere. They are solids that

are created from the liquid.

These precipitations occur over time when there is more of a substance in

the wine then the wine can hold. It's no different than a cloud trying to hold

more water vapor than the climatic conditions will allow. The clouds will

precipitate the water in the form of rain.

Temperature is a big factor in determining if a precipitation will occur in a

wine. To take our weather example a little further, the warmer the air gets

the more likely the clouds will produce rain. The opposite holds true as

well.

The same is true for wine, certain solids are more likely to precipitate out

of the wine when it is warmed up. There are also certain solids that are

more likely to precipitate out of a wine when it is cooled down.

Some wines will not precipitate anything regardless of temperature.

These wines are said to be "temperature stable". But in general, most

wines will precipitate something when taken to an extreme, whether it be

hot or cold.

Most of the precipitation that occurs in wine is caused by from either

excessive tartaric acid or excessive tannin. Tartaric acid is the major

source of acid found in grapes. Tannin, also known as tannic acid,

comes from the skins and stems of the grape as well as many other fruits.

When their concentration levels are beyond the saturation point of that

particular wine, at a particular temperature, then precipitation will occur

when given enough time. Quite often it will show up several months after

the wine has been bottle, making a perfectly good tasting wine become

visually unappealing.

*Tartaric Acid Precipitation.
This type of precipitation results as small, white to beige colored flakes

that will stay suspended in the wine for some time and then eventually

settle to the bottom in the form of cream-of-tartar. This type of precipitat-

ion is most commonly associated with white wines.

Wines that are stored in cooler areas are more likely to produce this type

of precipitation than wine stored at room temperature. But, it may occur at

any time with wines that have extremely high levels of tartaric acid.

*Tannic Acid Precipitation.
This type of precipitation will be seen as a dark, dusty deposit on the

bottom of the bottle. You will find this type of precipitation almost

exclusively in heavier red grape wines, such as Pinot Noir, and also in

darker berry wines - elderberry being the primary candidate.

Unlike tartaric precipitation, tannic precipitation is more likely to occur

when the wine is stored at a warmer temperature. But, it may also occur

very slowly at cooler temperatures in wines that are extremely heavy in

tannin.

The dark deposit that is created by this type of precipitation is not the

tannic acid itself, but rather tannic acid that has bonded with various

types of proteins in the wine - usually color pigmentation.


- Temperature Stability Tests

Before getting all bent out of shape thinking your wine is going to

"flake-out", there are a couple of simple tests that you can perform on a

given wine to determine if it is unstable and has the potential for

precipitation.

*The first test is the "cold stable test". Take a small portion of the wine,

say about 1 cup, and freeze it. After it has frozen solid, then allow it to

thaw. If you see an abundance of creamy looking flakes, then your wine

is not cold stable.

*The second test is the "heat stable test". Take a small portion of the wine

and bring it to just short of boiling then allow it to cool down for a few

hours. If you see an abundance of dark dusty looking precipitation, then

your wine in not heat stable.

Now realize, that a little bit of precipitation in either one of these tests is

okay. We are taking the wine to both extremes - temperatures they will

never actually encounter during storage, so a little bit of precipitation is

acceptable.

Also, it is important to note that these tests should only be performed on

wines that have been given an abundance of time to settle out the yeast

and fiber particles from the fermentation. Otherwise, you will get these

items depositing as well, making it hard to determine these tests' results.


- What Can You Do About It?

It is important to note here that filtering has no effect on whether a wine

will precipitate or not. A beautifully filtered wine can become cloudy or

with ugly deposits just the same as an unfiltered wine. So filtration is not

the answer to this type of problem. However, there are a couple of things

you can do to help eliminate the chance of these deposits from occurring

in your bottles.

*Cold Stable Treatment.
If you have determined that your wine is not cold stable, then you should

treat it by cooling the entire batch down to 35 to 45 degrees Fahrenheit

for 1 to 2 weeks before bottling. The idea here is to cause all of the

excess tartaric acid to precipitate out now, so that it will not occur later

in the bottles.

To help trigger the precipitation, it is recommended that you add 1/4

teaspoon of cream-of-tartar crystals for each gallon of wine. This is the

same cream-of-tartar you will find in the spice section of your local

grocery store.

To speed up the process, gently stir the wine once a day or on occasion

to keep the flakes suspended, so that they may attract more precipitation.

*Heat Stable Treatment.
The most effective way to heat stabilize a wine is to heat it up. Unfortun-

ately, this is not a practical solution because of the other effects heat has

on wine such as oxidation and denaturing.

If you have determined that your wine is not heat stable, the best coarse

of action is to treat it with a full dose of Bentonite. Bentonite is a clarifying

agent that is regularly used by wineries. Not only does it effectively clarify

particles that may be linger from a fermentation, it also has the ability to

induce protein precipitation, which is what tannic acid would eventually

cause on its own if left untreated.

To help trigger the precipitation, it is recommended that you add 1/4

teaspoon of wine tannin for each gallon of wine. This should be done at least

a few hours before the Bentonite treatment is performed.

* For more information on how to use Bentonite, read the following article:

"Using Bentonite As A Wine Clarifier"

* For more information about the Bentonite we offer, go to:

Speedy Bentonite

* For more information about the Tannins we offer, go to:

Wine Tannin