Brief Description:
Titratable acidity is an acidity measurement for wine and other foods that is most useful in determining acid content for sensory description. A titration of sorts is performed in the mouth of the consumer, where basic saliva meets the wine/food and causes increased flow.
The titratable acidity assessment can be performed in a number of ways, but the most common method is taking a sample of the wine/food (often 10ml) and titrating with an alkali solution (usually 0.1N NaOH) to an endpoint using phenolphthalein indicator (Salder and Murphy, 2003). The calculation of titratable acidity is:
%acid (w/w) = [N (normality of titrant) x E (volume of titrant) x EQ (equivalent weight)] / [W (mass of sample) x 1000]
It is worth noting that the TA found is less than (70-80% of) what is expected from the analytical tartaric and malic acid concentrations (Bouton, 1980).
Application in Wine Microbiology:
According to Boulton et al. (1996), “titratable acidity has no known effect on chemical or enzyme reactions or microbial activity.” That is not to say that the acid content in wine has no effect on microbial flora and vice versa. Malolactic acid bacteria, as their name implies, can convert malic acid to lactic acid, thus deacidifying the product (Jackson, 2008). Also, since acidity in wine is correlated with pH (Boulton, 1980), and because microbes are to some extent pH sensitive, it can be important in microbial stability.
References:
- Sadler, G.D. and P.A. Murphy. 2003. Chapter 13: pH and Titratable Acidity. In: Food Analysis. S.S. Nelson, ed. Kluwer Academic. New York.
- Boulton R.B. et al. 1998. Principles and Practices of Winemaking. Kluwer Academic Publishers. Boston.
- Bouton, R.B. 1980. The Relationships between Total Acidity, Titratable Acidity and pH in Wine. American Journal of Enology and Viticulture. 31(1): 76-80.
- Jackson, R.S. 2008. 7: Fermentation. In: Wine Science. Elsevier. San Diego.