During fermentation, under the direction of yeasts, the sugar is converted to alcohol and CO2

What you are left with, is an unstable chemical cocktail, that is ready to go in 1 of several directions……you may get the formation of aldehydes, acetic acid, ethyl acetate, geranium, all depending upon how the wine is stored, and what it comes into contact with.

Natural oxidation, and reactions caused by other yeasts and bacteria can lead to these changes.

A question was posted on the Internet just recently, that indicated that the winemaker was in need of help, as he did not really understand what he should be doing.

"I have just finished some California reds, all of which have gone thru Malo Lactic, and they are sitting in glass or barrels. Comes the annual question of stabilization. I can cold-stabilize in the garage over the next few weeks and / or add potassium sorbate to the wines to stabilize them.

Geraniums !! is what comes up as a threat every year. I read 3 different cautions on the issue:

1. Don't add sorbate if it has gone thru ML, else you will get the dreaded geranium curse
2. If it has not gone thru malo, hit it with high potassium metabisulphite, then with sorbate
3. Just give it a super cold-stabilization and forget the sorbate HELP ! "

Which of these statements is correct, assuming that this person is trying to make a dry red wine?

We have worked to produce as good a wine as we can, and we want to protect it from the effects of oxidation and bacterial / yeast spoilage.

What characteristics of wine do we have to consider when we are trying to stabilize a wine?

We can build a wine to have 16 % alcohol, a TA of 1.0, a pH of 2.8, a Free SO2 level of 120 ppm , and a sorbate level of 500 ppm………it might last for centuries, but would we ever drink it and find enjoyment,,,,,,,,,,,,not likely.

Lets look at these items individually.

Acid balance
I do not give absolute figures here, as each wine will be able to hold a different amount of acid to make it well balanced. For dry red table wines a range of 0.60 - 0.70 % is considered acceptable For dry white table wines a range of 0.65 - 0.75 % is acceptable

If you are aiming to produce sweeter versions of each type, you will probably want to have an extra 0.1 - 0.15 % more acid.

What does acid do ? It brings a wine to life. It balances off any sweetness that may be added to the wine.

Too much acid causes a sharp biting feeling along the edges of the tongue. Uncomfortable.

Acid can be measured and determined as Total Acid or TA. Doing this test will allow you to find out the current level of your wine, but it will not tell you if the wine is balanced. A big Chardonnay or Cabernet will be able to carry more acid than a thin Seyval or a Pinot.

So, let taste be your final deciding factor. Measure the level, taste it, does it call for more acid theoretically and taste wise ? If so determine how much you need and add it step-wise, mixing and tasting as you go. You may find that the theoretical level is just too much for your wine, or conversely, when you have added acid to a big wine, it is still too low to be well balanced.

Reducing acid levels:

Cold stabilizing
put your wine in a cold place, not lower than -10 C for a week or 2 This will cause Pot Bitartrate to fall out, reducing the acid level Blending
if you have a similar wine with low acid, try mixing the 2 Chemically
you can use Calcium Carbonate, which I don't like too much or you can use Pot Bicarbonate (0.9 gm / L will reduce the TA by 1 gm / L) Refer to Modern Winemaking by Philip Jackisch for further details) Increasing acid levels:

Tartaric Acid
1 gm / L for each increase of 1 gm / L TA This acid can be used anytime during the process, but some may fall out as Pot Bitartrate during cold stabilization Citric Acid
use 0.85 gm / L for each increase of 1 gm / L TA Do not use prior to fermentation as some bad reactions can occur Again, you are striving for a good balance in acid level, Measure and make adjustments, but always allow your mouth to be the final judge. pH

The pH of a finished wine will range from 3.2 to 3.6 for a good sound wine.
Too low, and the yeast may have trouble growing.
Too high, and you may see a wine heading for the drain.
pH is a measurement of hydrogen ion concentration. It will be affected by reducing or increasing the TA of the wine, but not in a direct and predictable way. Use it as a means of looking at the general health of your wine or must

Malo Lactic fermentation

This is the action of ML bacteria and their conversion of malic acid (sharp) to lactic acid (softer) This can happen spontaneously as these bacteria are present on the grape skins and thus in the "must", and cause desirable flavour changes in Chardonnays and Cabs for example..
It is most desirable to have this reaction occurring before the wine is bottled.
The addition of a commercial starter will usually guarantee positive results.
Most winemakers will add it at or near the end of the fermentation period.
Just be sure that the free SO2 level in the "must" is not over 20 ppm.
ML fermentations in the bottle can lead to sedimentation , blown corks, and off flavours.
The ML bacteria are not wanted in Germanic style wines, as they will reduce the natural fruity character.
The use of a good level of SO2 , 50 ppm and above will usually prevent this from occurring.
Before bottling , it is a good idea to check to see if the ML fermentation has occurred. There is a simple paper chromatography test available for this.

Alcohol levels

The lower the alcohol level, the greater the chance of a wine spoiling. Most low alcohol wines that you see in the market are probably membrane filtered to remove all spoilage organisms.

This is something that is usually beyond the means of amateur winemakers.

Wines that are in the 12 - 13 % level, are much more stable than wines in the 10 - 11 % range

Sulphur Dioxide (SO2)

This is routinely added as Potassium Metabisulphite. It has been used for centuries as an antioxidant and an antimicrobial. If you try to make wine without this item, you are playing with fire, as things can spoil very quickly. A number of years ago, I tried keeping my levels in the 20 - 25 ppm range, and soon learned that 50 - 60 ppm makes my wine much happier.

There are 3 forms of SO2 in wine
Total the sum of all of the sulphite in the wine. A good part of it will be bound to other organic molecules and offers no protection to the wine
Free this part is useful in protecting the wine from oxidation Molecular this part is the antimicrobial form and preserves the wine from bacteria

In most cases, when people refer to SO2, they are talking about the Free Sulphite (SO2).

There is a distinct correlation between Free / Molecular SO2 and pH (see chart )

The lower the pH, the lower the requirement for SO2 in the wine. Generally speaking, it is safest to keep the Free SO2 in the 50 - 70 ppm range.

How do we add SO2 ?

Some people like to use Cambden tablets - 1 tablet / gallon of wine yields 50 ppm SO2
I prefer to add Potassium Metabisulphite - ¼ tsp / 20 liters yields 40 ppm SO2
SO2 is effective for controlling the growth of Bacteria.

What happens if you end up with a wine that has too high a SO2 level ?

You can add 0.7 ml of 3 % Hydrogen Peroxide / gallon of wine, to reduce the SO2 level by 10 ppm.

Potassium Sorbate

This is an antifungal (yeast) agent. When added to a "clean" wine at approx 250 ppm - it will prevent the growth of yeast, and allow one to make an off-dry wine. It is not meant to be added to a fermenting wine, to try to get it to stop fermenting at a certain level. There is just too much happening, and the chances of the sorbate molecule going into other metabolic pathways is just too great. You could end up with some very unpleasant properties.

It can be added in several forms:
Pure Potassium Sorbate - dissolve in a little water, and add to the wine
Wine conditioners - add directly to the wine as per instructions if there are any. Checking a couple of them……….1 said use 2 - 4 oz / gal………..another had no addition rate. This is a little like playing with a loaded gun, as I will demonstrate.

I made a very nice Muscat several years ago, but it was a little tart, so I decided to add just a little wine conditioner. After trying several addition rates, I came up with what I thought was a pleasant wine. Open bottle and watch wine fizz. What happened. Obviously there wasn't enough Potassium Sorbate to stop the remaining yeast from re-fermenting. I didn't add as much as the label said, because it made the wine too sweet for my taste.

One very important note - Make sure that you have at least 50 ppm of SO2 in the wine Otherwise - ML bacteria which can be present, can turn the Sorbate to Geranium

Sweetening Wines

There are a number of styles of white wines that can be enhanced by the addition of some sweetener.

What can we use ?

Table sugar is the simplest, but you can use other sugars or even eserved grape juice.

The problem now is to stop the yeast from re-fermenting in the bottle.

What do we do ?

It is best if the wine has been filtered to at least a # 2 pad, or better still thru a # 3 pad filter. Theoretically, this has removed all of the yeast, but we do not live in a perfect world, and some will always find their way into the wine.

Let's protect the wine.

Add SO2 - for a sweet wine, I would have at least 50 - 60 ppm SO2 in the wine at bottling time
Measure with a Titrette, before adding sugar to the wine. What ever the reading is, bring it up to the 50 - 60 ppm level

It you test it and it reads 30 ppm, add just under ¼ tsp of Pot Metabi

Add Potassium Sorbate - use 250 ppm
250 ppm = 250 mg/ L = 0.25 gm/ L

If you are making a 19 L carboy, you need 19 x 0.25 = 4.75 gms of Pot Sorbate

A scale is very beneficial here. Without one you will have to go by a rough rule of thumb. One tsp is approx equal to 3 gms of Pot Sorbate….so just over 1 ½ of a tsp should be pretty close.

Another way to add a light touch of sweetness, is to use Glycerine that you can buy in a pharmacy. Glycerine does not have the sweetening power of sugar, but if you just need a touch of sweetness, it is very good. It does not ferment, so you don't have to worry about re-fermenting. I use anywhere from 2 - 4 ml / L It's a matter of taste.

How much sugar do I use ? This really becomes a matter of personal taste. I will make up a sample (say 200 ml) that I know is going to be too high for my taste, say 4 gm of sugar / 100 ml of wine. I use a graduated 100 ml cylinder, but you can obtain graduated syringes from a pharmacy to measure out specific amounts. I usually have several sizes on hand

I will pour some into a glass and use it as a reference point I will then add equal proportions of the dry wine and the sweet wine - this gives me 2 gm / 100 ml
I can then make a blend of 3 parts dry and 1 part sweet to give me 1 gm / 100 ml
One part dry and 3 parts sweet gives me 3 gm / 100 ml
Line them all up in order….dryest to the left…..go down the line from left to right until you find a level you like. Call in the significant other and have her / him repeat the test. Come to a compromise, and you know where you want to be.

If you decided that you wanted an extra 2 gm of sugar / 100 ml. Then that equates to 20 gm / L or 20 x 19 = 380 gms for a 19 L carboy.

Pay attention to the acid at this time. You may get the sweetness you want, but the wine could go "flabby" as the acid may not be able to carry the amount of sugar you put in.

You may have to go thru the same exercise with different acid levels.

COVA 2001 COVA Homepage www.littlefatwino.com