Juice and Wine Acidity(book excerpts)
In wine tasting, the term acidity refers to the fresh, tart and sour attributes of the wine which are evaluated in relation to how well the acidity balances out the sweetness and bitter components of the wine such as tannins. The balance is challenging as too much acid may make a wine tart or sharp, while too little may make a wine flat or flabby. Acids can arise in the grapes themselves such as tartaric, malic, and citric acids and carry over into the wine. However, there are also some acids including acetic, butyric, lactic, and succinic acids that arise during the course of winemaking from either yeast and/or bacteria. Chemically these acids influence the wine's acidity which affects taste and pH which affects color, oxidation, and consequently the overall lifespan of a wine. Acidity in wine is customarily divided into two categories, volatile and titratable. Volatile acidity (VA) refers to acids that can be readily removed by steam distillation, whereas titratable acidity (TA) is a measurement of the total concentration of titratable acids and free hydrogen ions. Strength of acidity is measured according to pH, with most wines having a pH between 3.0 and 4.0. Adjusting the acidity is an important part of the winemaking process. The addition of acid to grape juice, must, or wine will decrease the pH and increase TA of the wine. The amount of acid needed to correct the acidity deficiency depends on the total acidity, the pH, and the buffer capacity of the juice, must or wine. Deacidification is the process of reducing titratable acidity in grape juice, must, or wine.
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Topics Within This Chapter:
- Titratable Acidity
- Relationship Between pH and TA
- Buffering Capacity
- Adjusting pH or Titratable Acidity
- Why is pH Important?
- pH and TA for White and Red Wines
- Analyzing Titratable Acidity
- Volatile Acidity
- Sources of Volatile Acidity
- Threshold Levels
- Analyzing Volatile Acidity
- Acidification of Must and Wine
- Acidification Correction Methods
- Acid Addition
- Deacidification of Must and Wine
- Deacidification Correction Methods
- Chemical Treatment
- Reverse Osmosis
- Biological Deacidification