When making a fresh ingredients wine, it is extremely important that you adjust the sugar and acids into the proper ranges. Too much or too little of either can create problems in your fermentation, including failure to ferment, and problems in your finished wine.
Acids are the components that give a wine structure and complexity. Excessive acidity is considered a fault in wine and will result in an unbalanced wine that will taste green or tart. On the other hand, not enough acid will result in flabby wine that lacks structure and will not last long. As a general rule of thumb, country wines should have a TA (Titratable Acid) of .60%, while red grapes are .65% and white grapes are .75%. Titratable acidity relates to the amount of acid in solution as a percentage of volume or as grams per liter. In other words a TA of .60% equals 6 g/l (grams per liter).
With the aid of the trusty hydrometer, adjusting sugar is fairly straightforward; however, testing and adjusting the acid is not quite as easy. An inexpensive acid test kit is available, but its use is not as intuitive as the hydrometer. As a result, I hope the following will make using the acid test kit easier and will produce meaningful calculations.
The Acid Test Kit (also known as an acid testing by titration kit.) that we sell contains the following items:
- One plastic calibrated syringe
- Plastic testing cup
- 5 fluid ounces of 1/5th normal Sodium Hydroxide Solution
- 1/2 fluid ounce of Phenolphthalein Color Solution in a drop dispenser bottle
Before we start, please note that any samples used in this test MUST not be returned to the wine. Sodium Hydroxide is poisonous. As a result, please dispose of all samples! Also please be very careful when handling Sodium Hydroxide, as it is corrosive and can cause burns and permanent eye damage.
- Start the titration test by withdrawing 15cc of wine and placing it in the plastic testing cup.
- Next, add 3 drops of the Phenolphthalein Color Solution to the sample.
- Wash out the syringe and draw in 10cc of the Sodium Hydroxide Solution. At this point in the test you are looking for a noticeable color change. For white wines, you are looking for a change to a pinkish color. For red wines, you are looking for a blue/gray/green color. When you reach this point and adding additional Sodium Hydroxide does not change the color, the end-point has been reached. To find the color change, add the Sodium Hydroxide Solution to the test sample .5cc at a time and agitate the sample after each addition. Repeat this process until you note the color change.
- Each cc of Sodium Hydroxide required to attain the color change represents .1 of acid expressed as TA If 6 cc's of Sodium Hydroxide are used, the wine has a TA of .60%. If you are making a country wine, your acid is at the correct level and no further adjustments are required. If you are making a red or white grape wine, you will need to add enough acid to bring the TA up to .65% or .75%, respectively.
- To raise the acid, 1 tsp. of Acid Blend per gallon of must, will raise the acid level by .15%. For example, if you are making 1 gallon of country wine and the initial TA was .30%, you will need to add 2 tsp. of acid blend to raise the TA to .60%. For 5 gallons, you will need 10 tsp. to accomplish the same.
Most fruits used in country wines are low in acid which require the addition of acids; however, some wines, as well as most native American grapes are high in acid and the TA needs to be reduced. We will discuss these options in next month's newsletter.
It should also be noted that both of the chemicals used for the acid titration will deteriorate when exposed to air. Be sure to keep the lids on tight when not using these chemicals and keep them away from children. In addition, not all Acid Test Kits use the same strength of Sodium Hydroxide. As a result, be sure to follow the instructions included with your kit.