You may have noticed that some wineries provide technical sheets for their wines. These sheets often contain a bunch of acronyms - pH, TA, RS, and ABV. Ever wonder what they mean and whether you should care? Let’s demystify this alphabet soup of wine.
pH stands for potential of hydrogen or power of hydrogen. It measures the acidity or alkilinity of an aqueous solution. The pH scale ranges from 1 to 14, with 7 being neutral. Wine is acidic, and its pH usually runs in the 3’s. White wines pH is typically in the 3.0 to 3.6 range, and red wines in the 3.4 to 3.9 range. Wines with lower pH tend to be more puckering on the palate, while wines with higher pH tend to be rounder. Think lemon juice versus tomato juice.
In the vineyard, pH is used in conjunction with TA (or Titratable Acidity), sugar, and flavor to determine the optimal time for harvest. pH in grapes increases as they ripen and further rises incrementally during the fermentation process. If pH is lower than 3.0, it may be an indication that the grapes have been harvested before they are fully ripened. The resulting wine flavor may not be well developed. The reverse is true if pH is more than 4, suggesting a flabby wine with little acidity to liven it.
Fun Fact: Acidity acts as a buffer to preserve wine. Wine collectors often favor a vintage with a lower pH for cellaring. TA
TA is often used to refer to Total Acidity and Titratable Acidity interchangeably. The truth is that Total Acidity is the measure of both titratable and non-titratable acids. However, because Titratable Acidity is easier to derive, it is often used as an approximation of Total Acidity. In this blog post, TA refers to Titratable Acidity. A good TA range for white wines is 7-9 g/L and that for red wines is 6-8 g/L.
While pH measures the intensity of acids, TA measures the concentration of acids. To illustrate the difference between pH and TA, let’s make a Bloody Mary.
1. Mix 0.5 oz of lemon juice to 2 oz of vodka and taste it. It will likely pucker you up!
2. To that, add 4 oz of tomato juice, mix, and taste again. It will taste less sour.
Both lemon juice and tomato juice are acidic ingredients. However, lemon juice contains citric acid which has a low pH of 2, while tomato juice contains a blend of citric, malic, and ascorbic acids with a combined pH of 4.1 to 4.4. So even though the concentration of acids (or TA) in the drink has increased with the addition of the tomato juice, the intensity of the combined acids has decreased.
3. Now add your Worcestershire sauce, Tobasco sauce, horseradish, celery salt, and all the other good stuff and enjoy!
Fun Fact: While some wine collectors use pH as an indication of good acidity and therefore aging potential, others use TA as a measure. A vintage with a higher TA is definitely preferred for aging to a vintage with lower TA.
RS stands for residual sugar, the leftover grape sugar after alcoholic fermentation is completed. RS is measured using g/L or %. (10 g/L is 1% residual sugar.) Most dry wines will have close to zero residual sugar so you don’t typically see RS listed in the tech sheet. Sweet wine starts at about 35 g/L or 3.5% RS and can go up to over 200 g/L or 20% RS.
Some of the best sweet wines are produced as a result of botrytis
, also known as Noble Rot. Botrytis
is a type of fungus that causes grapes to shrivel. As water content evaporates from the grapes, the sugar level increases and intensifies. This causes alcoholic fermentation to complete with excess sugar remaining. Famous botrytized wines include French Sauternes, Hungarian Tokaji, and German Beerenauslese or Trockenbeerenauslese.
Fun Fact: The most expensive botrytized wine is the Royal Tokaji Essencia that at one point cost $40,000 a bottle. The last I checked, you can get a half bottle for about $1,000.
Last but not least, ABV stands for Alcohol by Volume. It measures how much alcohol is in 100 mL of wine and uses % as the unit of measure. ABV of a wine is dependent on the grape sugar pre-fermentation. During alcoholic fermentation, wine yeast converts grape sugar into ethanol. Wine grapes or vitis vinifera often reach 22 to 26 degrees Brix (symbol °Bx) by harvest. 1 °Bx is 1 g of sugar in 100 g of crushed grape juice and will yield about 0.55% in alcohol content. 22 to 26 °Bx will yield about 12.1 to 14.3% ABV.
While most new world wines tend to run high in ABV, some European wines have less than 10% ABV. Moscato d’Asti runs around 5-6% ABV, and German Riesling runs around 7-8% ABV. By law, these old world wines are required to stop fermentation before all the sugars are converted to alcohol to create the respective styles of sweet wines.
Fun Fact: In the United States, the alcohol excise tax for wine above 16% ABV is about 50% higher than that for wine at 16% ABV and below. For that reason, you will not see many bottles of wine (if any!) with ABV above 16%.
I hope you enjoy the demystifying of the alphabet soup of wine and gain some confidence in reading wine technical sheets. And if you are hoping to start a wine cellar, you are now armed with a bit more knowledge on how to pick wines with aging potential. Salud!