Testing Wine Musts For Sugar, pH, and TA

Making wine is a fun and rewarding area of homebrewing. While you can make it simply by mixing the components to a kit together, setting, and forgetting; you can increase the quality of your wine by testing and adjusting your wines gravity, pH, and TA accordingly.

Testing Sugar in Wine

testing wine sugarThe testing of sugar in must is simple and needs only 2 pieces of equipment. First, a wine hydrometer and second a tall test flask. The test flask, when filled with water must allow the Hydrometer to float without touching the bottom of the flask. If the hydrometer touches the bottom you won’t be able to read whether you’re must has a low baumé or brix. Fill the flask with a sample of your must, leaving enough space that it won’t over flow when you introduce your hydrometer.

Make sure that any bubbles at the surface of the must are blown off as this can add buoyancy to the hydrometer and give you a false reading. Place the hydrometer into the flask and shake off any bubbles that may cling to it under the surface then once the hydrometer has stopped moving you will be able to take a reading. Sugar in wine is commonly measured by baume or brix in Australia. 1 degree of baume translates to 18g/l of sugar and roughly ferments to 1% of alcohol. 1 Brix translates to 10g/l therefore 1.8 Brix is 1° baume. For white wine the desired baume is 10.5°-13.5° (19-24.3 Brix) depending on the variety and for red wine 12.5°-15.5° baume (22.5 Brix- 28 Brix).

It is worth noting that most hydrometers are calibrated to read accurately at 68°F ( 20° Celsius). If your must is warmer or colder than this you may need to use a hydrometer temperature adjustment calculator.

Testing pH in Wine

testing wine pHTesting the pH of your must will tell you how strong the acid is in your must. The lower the pH reading the greater the acidity. Most winemakers aim for a pH of 3.0-3.4 for white wines and 3.3-3.6 for reds. Lower pH makes the wine more stable and protects against bacteria. Measuring the pH of your must is simple with the right equipment. A pH Meter is required, once calibrated, it is simply a matter of inserting the clean probe into the must and stirring slowly until the pH meter returns a reading. Once the reading is returned you can adjust the pH accordingly.

Testing TA (Titratable Acid) in Wine

The simplest and most inexpensive way to test TA is with an acid test kit. These generally come with a test tube, syringe, sodium hydroxide and phenolphthalein. Different kits may have different instructions so read these carefully before testing, however as a general rule place approximately 15mls of must into the tube then place 3 drops of phenolphthalein with the must and shake to mix. With the syringe draw 10ml of sodium hydroxide (be careful as this is caustic) and slowly add 0.5ml to the tube shaking to mix. Watch the color change (pink for reds, grey for whites) if the must changes back to its original color add another 0.5ml of sodium hydroxide and repeat until the must does not return to its original color i.e. it stays grey or pink. Then you calculate how much sodium hydroxide was added before the color remained changed. 1ml equates to 0.1% TA so if 4mls of sodium hydroxide was added when the must stopped changing back to its original color the TA is 0.4% (4g/l).

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You can also test TA using a pH meter by placing the probe in 15ml of must then add sodium hydroxide as above until the PH meter reads 8.2 and then calculate the percentage of TA with the same formula above. The ideal TA range for white wine is 6-9g/l and 6.0-7g/l for red wines.

Adjusting pH and TA:

Adjusting pH and TA is a balancing act. To raise your TA you will need to add acid, this however will lower your pH. Approximately 1g/l of tartaric acid will reduce the pH by 0.1. In most instances you will be adjusting acidity up, not down, however if you do feel the need to lower the TA (higher pH) you can use calcium carbonate. 1g/l will increase the pH by 0.1 but decrease the TA. Lowering TA is only recommended for must that has extremely high TA and low pH. Small amounts of water can be added to lower the PH also but again is not recommended as it can make your wine 'watery'.

About the Author

Jack has 12 years worth of experience in the wine industry and is an avid home brewer.

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written by Jack Davis

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