Difference between revisions of "Titratable Acidity"
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| − | + | '''Titratable Acidity''' (abbreviated as ''TA'') is an approximation of the ''Total Acidity'' of a solution, and is often used in the production of wine. It is expressed in units of grams per liter (g/L). ''Titratable Acidity'' is often mistakenly confused with ''Total Acidity'', but they are not the same thing (see reference). While ''Total Acidity'' is a more accurate measurement of the total acid content of a solution, ''Titratable Acidity'' is usually used because it is easier to measure <ref>[http://wineserver.ucdavis.edu/pdf/attachment/220%20relationship%20between%20total%20acidity,%20TA,%20and%20pH%20.pdf The relationship between total acidity, titratable acidity and pH in wine. Roger Boulton. American Journa l of Enology and Viticulture. 31(1): 76-80. 1980.]</ref>. ''TA'' has also proved to be a useful way to measure acidity in sour beer <ref>[http://blog.ocbeerblog.com/2015/04/13/how-sour-is-your-sour-beer/ How Sour is Your Sour Beer?. OCBeerBlog on Firestone Walker's demonstration of the uses of TA measurements. April 13, 2015.]</ref>. | |
| − | Many sour beer producers use pH to help determine how "sour" their beer is in relation to a set goal, previous batches, or commercial examples. | + | ==TA versus pH== |
| − | + | Many sour beer producers use pH to help determine how "sour" their beer is in relation to a set goal, previous batches, or commercial examples. However, often times TA is a more useful measurement of how acidic a beer will be perceived on the palate. | |
| − | |||
| + | ===pH=== | ||
In chemistry, pH is the negative log of the activity of the hydrogen ion in an aqueous solution. Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline. Pure water has a pH of 7. | In chemistry, pH is the negative log of the activity of the hydrogen ion in an aqueous solution. Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline. Pure water has a pH of 7. | ||
| − | The pH scale is traceable to a set of standard solutions whose pH is established by international agreement. | + | The pH scale is traceable to a set of standard solutions whose pH is established by international agreement <ref name="bates">Bates, Roger G. Determination of pH: theory and practice. Wiley, 1973.</ref>. Primary pH standard values are determined using a concentration cell with transference, by measuring the potential difference between a hydrogen electrode and a standard electrode such as the silver chloride electrode. Measurement of pH for aqueous solutions can be done with a glass electrode and a pH meter, or using indicators. |
| − | pH measurements are important in medicine, biology, chemistry, agriculture, forestry, food science, environmental science, oceanography, civil engineering, chemical engineering, nutrition, water treatment & water purification, and many other applications | + | pH measurements are important in medicine, biology, chemistry, agriculture, forestry, food science, environmental science, oceanography, civil engineering, chemical engineering, nutrition, water treatment & water purification, and many other applications <ref name="bates"></ref>. |
pH is best tested in sour beers using a [[PH Meter]] and is most useful for biological parameters. Cells live or die based on pH, not TA. This means pH should be used when testing sanitizer, sour worting, starter cultures, etc. | pH is best tested in sour beers using a [[PH Meter]] and is most useful for biological parameters. Cells live or die based on pH, not TA. This means pH should be used when testing sanitizer, sour worting, starter cultures, etc. | ||
| − | ==Why TA?== | + | ===Why TA?=== |
| + | When attempting to use pH for sensory parameters (how sour something tastes), the measurement falls short. Humans perceive acidity from tasting acids, not H+ ions. In a strong acid, the amount of acid is always proportional to the amount of H+ ions. However, lactic acid, the primary acid in sour beer, is a weak acid. For various reasons a weak acid does not completely ionize/dissociate. | ||
| − | + | Any acid not dissociated (in other words, an acid still holding onto its H+) does not affect pH. On the other hand, humans will perceive an increased "sourness" based upon the amount of acid in a beer, dissociated or not. The best way to test for total acidity, regardless of dissociation, is using a test called ''Titratable Acidity''. | |
| − | + | Kara Taylor at White Labs has done a reasonable amount of professional sensory panels showing the correlation between ''TA'' and perceived sour taste, as well as showing no correlation between pH and sour taste. Her full presentation, where most of this information was sourced, is available to any attendee of the 2015 Craft Brewer's Conference. | |
| − | |||
| − | Kara Taylor at White Labs has done a reasonable amount of professional sensory panels showing the correlation between TA and perceived sour taste, as well as showing no correlation between pH and sour taste. Her full presentation, where most of this information was sourced, is available to any attendee of the 2015 Craft Brewer's Conference. | ||
==Testing for Titratable Acidity in Sour Beer== | ==Testing for Titratable Acidity in Sour Beer== | ||
===Equipment Requirements:=== | ===Equipment Requirements:=== | ||
| − | |||
# pH Meter with Automatic Temperature Correction | # pH Meter with Automatic Temperature Correction | ||
# Buffer/Testing Solutions for pH Meter | # Buffer/Testing Solutions for pH Meter | ||
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===Procedure=== | ===Procedure=== | ||
| − | + | # Calibrate the pH meter. | |
| − | # Calibrate pH meter | + | # Pipette 50mL of decarbonated beer into the beaker. |
| − | # Pipette 50mL of decarbonated beer into beaker | + | # Place the pH probe and the ATC thermometer into the beaker, submerge tip of the probe into the beer. |
| − | # Place pH probe and ATC thermometer into beaker, submerge tip | + | # Fill the buret with 0.1N of NaOH. |
| − | # Fill buret with 0.1N NaOH | + | # Open the Stopcock and add the NaOH to the beer until pH meter reaches a reading of pH 7.0. |
| − | # Open | + | # Upon reaching 7.0 pH, slowly add more NaOH until pH meter reads exactly pH 8.2, keeping track of how much NaOH is added. |
| − | # Upon reaching 7.0, | + | # Record the total amount of NaOH used to reach pH 8.2. |
| − | # Record total amount of NaOH used to reach pH 8.2 | + | # Use the following formula to find the ''Titratable Acidity'': '''Titratable Acidity = (mL 0.1N NaOH * 0.9) / (mL beer * S.G.)''' |
| − | # Use the following formula to find Titratable Acidity: | + | # The number you get is TA in grams/L. |
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| − | |||
| − | |||
| − | The number you get is TA in grams/L. | ||
| − | |||
==Uses in Sensory & Further Reading:== | ==Uses in Sensory & Further Reading:== | ||
| + | * It may be best to compare the ratio of ''Titratable Acidity'' to ''Final Gravity'' as sweetness counter-acts acidity in sensory experiments <ref>Kara Taylor, White Labs - CBC 2015 Presentation "Sour Beer is More than pH"</ref>. | ||
| + | * More information on this procedure is available from the American Society of Brewing Chemists, who publish a similar set of procedures under the name "Total Acidity with Potentiometer". | ||
| + | * Jim Crook of Firestone Walker has created a presentation about blending sour beers using TA. Contact him for a copy. | ||
| − | + | ==References== | |
| − | + | <references/> | |
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| − | References | ||
| − | <references | ||
[[Category:Techniques]] | [[Category:Techniques]] | ||
Revision as of 14:12, 7 May 2015
Titratable Acidity (abbreviated as TA) is an approximation of the Total Acidity of a solution, and is often used in the production of wine. It is expressed in units of grams per liter (g/L). Titratable Acidity is often mistakenly confused with Total Acidity, but they are not the same thing (see reference). While Total Acidity is a more accurate measurement of the total acid content of a solution, Titratable Acidity is usually used because it is easier to measure [1]. TA has also proved to be a useful way to measure acidity in sour beer [2].
Contents
TA versus pH
Many sour beer producers use pH to help determine how "sour" their beer is in relation to a set goal, previous batches, or commercial examples. However, often times TA is a more useful measurement of how acidic a beer will be perceived on the palate.
pH
In chemistry, pH is the negative log of the activity of the hydrogen ion in an aqueous solution. Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline. Pure water has a pH of 7.
The pH scale is traceable to a set of standard solutions whose pH is established by international agreement [3]. Primary pH standard values are determined using a concentration cell with transference, by measuring the potential difference between a hydrogen electrode and a standard electrode such as the silver chloride electrode. Measurement of pH for aqueous solutions can be done with a glass electrode and a pH meter, or using indicators.
pH measurements are important in medicine, biology, chemistry, agriculture, forestry, food science, environmental science, oceanography, civil engineering, chemical engineering, nutrition, water treatment & water purification, and many other applications [3].
pH is best tested in sour beers using a PH Meter and is most useful for biological parameters. Cells live or die based on pH, not TA. This means pH should be used when testing sanitizer, sour worting, starter cultures, etc.
Why TA?
When attempting to use pH for sensory parameters (how sour something tastes), the measurement falls short. Humans perceive acidity from tasting acids, not H+ ions. In a strong acid, the amount of acid is always proportional to the amount of H+ ions. However, lactic acid, the primary acid in sour beer, is a weak acid. For various reasons a weak acid does not completely ionize/dissociate.
Any acid not dissociated (in other words, an acid still holding onto its H+) does not affect pH. On the other hand, humans will perceive an increased "sourness" based upon the amount of acid in a beer, dissociated or not. The best way to test for total acidity, regardless of dissociation, is using a test called Titratable Acidity.
Kara Taylor at White Labs has done a reasonable amount of professional sensory panels showing the correlation between TA and perceived sour taste, as well as showing no correlation between pH and sour taste. Her full presentation, where most of this information was sourced, is available to any attendee of the 2015 Craft Brewer's Conference.
Testing for Titratable Acidity in Sour Beer
Equipment Requirements:
- pH Meter with Automatic Temperature Correction
- Buffer/Testing Solutions for pH Meter
- Buret (100mL recommended) with Stopcock
- Buret stand (can be DIY)
- 250ml - 500ml Beaker (or pint glass, etc)
- 0.1N Sodium Hydroxide (NaOH)
- Accurate way to measure 50mL (can use the buret for this, but I recommend a serological pipette or high-grade graduated cylinder)
- Coffee filter or some other way to decarbonate beer (shake and vent repeatedly, pour through filter, etc)
- Hydrometer
Procedure
- Calibrate the pH meter.
- Pipette 50mL of decarbonated beer into the beaker.
- Place the pH probe and the ATC thermometer into the beaker, submerge tip of the probe into the beer.
- Fill the buret with 0.1N of NaOH.
- Open the Stopcock and add the NaOH to the beer until pH meter reaches a reading of pH 7.0.
- Upon reaching 7.0 pH, slowly add more NaOH until pH meter reads exactly pH 8.2, keeping track of how much NaOH is added.
- Record the total amount of NaOH used to reach pH 8.2.
- Use the following formula to find the Titratable Acidity: Titratable Acidity = (mL 0.1N NaOH * 0.9) / (mL beer * S.G.)
- The number you get is TA in grams/L.
Uses in Sensory & Further Reading:
- It may be best to compare the ratio of Titratable Acidity to Final Gravity as sweetness counter-acts acidity in sensory experiments [4].
- More information on this procedure is available from the American Society of Brewing Chemists, who publish a similar set of procedures under the name "Total Acidity with Potentiometer".
- Jim Crook of Firestone Walker has created a presentation about blending sour beers using TA. Contact him for a copy.
References
- ↑ The relationship between total acidity, titratable acidity and pH in wine. Roger Boulton. American Journa l of Enology and Viticulture. 31(1): 76-80. 1980.
- ↑ How Sour is Your Sour Beer?. OCBeerBlog on Firestone Walker's demonstration of the uses of TA measurements. April 13, 2015.
- ↑ 3.0 3.1 Bates, Roger G. Determination of pH: theory and practice. Wiley, 1973.
- ↑ Kara Taylor, White Labs - CBC 2015 Presentation "Sour Beer is More than pH"