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Three important elements in Winemaking. 1. pH 2. Acid (TA) 3. Sulfur Dioxide or SO 2 What is it? Why is it important? How is it tested? How is it adjusted?. pH. 1. What is it? 2. Why is it important? 3. How is it tested? 4. How is it adjusted?. What is pH.

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three important elements in winemaking
Three important elements in Winemaking

1. pH

2. Acid (TA)

3. Sulfur Dioxide or SO2

  • What is it?
  • Why is it important?
  • How is it tested?
  • How is it adjusted?

1. What is it?

2. Why is it important?

3. How is it tested?

4. How is it adjusted?

what is ph
What is pH
  • pH is a measure of the number of dissociated hydrogen ions present in a solution. Also referred to as potential of hydrogen.
  • uses an reverse, logarithmic scale from 0 -14 (pH of 7 being neutral). In wine making we will normally work in the 3-4 range.
  • a smaller pH value represents more hydrogen ions and a higher pH value represents less hydrogen ions.
  • For example, a wine with a pH value of 3.0 contains ten times more hydrogen ions than in a wine with a pH of 4.0. Consequently, the pH value of a solution becomes smaller as the acid content of the solution becomes larger.
what is ph con t
What is pH (con’t)
  • A solution containing a specific quantity of a relatively weaker acid such as malic and citric (found in many fruits) will have a different (higher) pH than a solution containing the same quantity of a stronger acid such as tartaric.
  • The pH value reflects the quantity of acids present, the strength of the acids and the effects of minerals and other materials in the wine
  • Many different factors are involved, but wine pH depends upon three major factors: (1) the total amount of acid present (2) the ratio of malic (or other acids) to tartaric acid (3) the quantity of potassium present.
1 the total amount of acid present
1. The total amount of acid present
  • Wine acids produce hydrogen ions, and pH is a measure of the number of hydrogen ions present in a solution.
  • Overall, wine pH will be lower when the titratable acid is higher which is normal in grapes. However, high titratable acid does not always produce low pH values.
2 the ratio of malic or other acids to tartaric acid
2. The ratio of malic (or other acids) to tartaric acid
  • Malic acid and other acids such as citric & lactic are weaker than tartaric acid, so wines high these acids other than tartaric acid can have a high TA and a high pH value.
  • Tartaric acid produces almost three times more hydrogen ions than malic acid, so gram for gram, tartaric acid produces a much lower pH than malic acid.
3 the quantity of potassium present
3. The quantity of potassium present.
  • Potassium reacts with tartaric acid in the juice and forms potassium bitartrate (cream of tartar). When alcohol accumulates during fermentation, the juice cannot hold all the additional potassium bitartrate, and some tartrates precipitate out of the liquid. These potassium bitartrate crystals are also known as wine diamonds.
  • When potassium bitartrate precipitates, the titratable acid of wine decreases, but wine pH may increase, decrease or stay the same. If the starting pH of the wine is 3.6 or less, the pH will become smaller as the bitartrate precipitates out of the wine. If the starting pH is 3.8 or greater, the pH will become larger as the bitartrate precipitates. Little change will occur when the starting pH falls between about 3.6 and 3.8.
why ph is important
Why pH is important
  • Fermentation with yeast (single cell fungi) and lactic acid bacteria (MLF)
  • Color Stability
  • Chemical and biological stability
  • SO2 Effectiveness
ph effect on fermentation
pH effect on Fermentation
  • Yeast (single cell fungi) growth does not change significantly over the normal range of wine pH values.
  • Proper pH can enhance production of fruity esters during yeast fermentation
  • On the other hand, wine bacteria do not tolerate low pH values, and wine pH strongly influences both bacterial growth rate and bacterial fermentation characteristics.
  • This is why malolactic fermentation is not likely to occur in wines with pH values lower than 3.3
ph effect on color stability
pH effect on Color Stability
  • Wines with low pH values generally have better visual qualities and more color stability.
  • Both red and white wines have better color stability due to much of the unstable color pigments precipitating out of the wine early in the winemaking process. After the unstable pigments are gone, wine colors are more stable.
  • In red wine the color intensity increases, and becomes more purple at low pH values.
  • In white wine the proper color is maintained and the risk of browning is greatly reduced
ph effect on the chemical and biological stability
pH effect on the chemical and biological stability
  • Lower pH values are well known to improve the stability, so winemakers usually prefer a pH range of 3.0 to 3.5. The wine is so stable in this range that many winemakers believe pH is a crucial guideline in winemaking.
  • Increases microbial stability through increased inhibition of bacterial growth.
  • Low pH also has a direct influence on the hot stability of wine. When bottled wines are stored in warm areas, protein can precipitate out of them, causing serious problems.
  • pH's higher than 4.0 should always be avoided as spoilage is more likely to occur above this level. (The optimum pH for bacterial multiplication is 4.2-4.5.)
ph effect on so 2 effectiveness
pH effect on SO2 Effectiveness
  • Molecular SO2 (which exists as either a gas or as single molecules in juice and wine) is the principal form of the free/unbound sulfur dioxide responsible for anti-microbial activity.
  • The amount of free SO2 needed for proper protection of your wine is a direct function of pH.
  • The lower the pH the less free SO2 is needed and the higher the pH the more free SO2 is needed for the same protection.
how is ph tested
How is pH tested
  • Normal pH Test Strips
  • Pros: Inexpensive ($4.50 per 100 strips) and easy to use
  • Cons: Least accurate and effected by colored or turbid sample
  • Accuvin pH Test Kit
  • Pros: Easy to use, not effected by color or turbid sample and fairly accurate compared to pH meter.
  • Cons: More expensive than strips ($18.00 per 10 tests)
  • Hand Held pH Meter
  • Pros: Very accurate (two decimal places) and most cost effective if you do lots of pH testing
  • Cons: Expensive to buy initially ($85.00) and more time consuming when using due to buffering.
lowering ph
Lowering pH
  • To raise the TA and lower the pH, the most efficient way is to add tartaric acid. Tartaric acid is one of the naturally present grape acids, and is not consumed by yeast (like citric acid is) or by any other microorganism in the winemaking process. What you add is what stays in the wine, unless it precipitates later with age or with cold stabilization.
  • Acid Blend is also used and contains a blend of tartaric, malic, and citric acid.
raising ph
Raising pH
  • Calcium carbonate and Potassium bicarbonate can be used to reduce the acid and therefore raise the pH. It works mainly on the tartaric acid in a wine/must.
  • Increasing the size of the batch with more ingredients is the best way to raise the pH to an acceptable level.
ph summery
pH Summery
  • Overall, wine pH will be lower when the titratable acid is higher which is normal in grapes. However, high acid does not always produce low pH values based on the type of acid present.
  • In addition to color stability proper pH (3.0-3.5) greatly increases the chemical and biological stability and SO2 Effectiveness (molecular SO2)
  • To lower the pH you need to increase the TA. The most efficient acid to use is tartaric acid.
  • Proper pH is important to the stability and long term protection of your wine.
wine acid ta
Wine Acid (TA)

1. What is it?

2. Why is it important?

3. How is it tested?

4. How is it adjusted?

what acids are found in wine
What Acids are found in Wine?
  • Tartaric:Few fruits other than grapes contain significant amounts of tartaric acid. One half to two thirds of the acid content of ripe grapes is tartaric acid, and it is the strongest of the grape acids. Tartaric acid is responsible for much of the tart taste of wine, and it contributes to both the biological stability and the longevity of wine.
  • Malic:Malic acid is prevalent in many types of fruit. This acid is responsible for the tart taste of green apples. Malic acid is one of the biologically fragile wine acids, and it is easily metabolized by several different types of wine bacteria. Unlike tartaric acid, the malic acid content of grapes decreases throughout the ripening process, and grapes are grown in hot climates contain little malic acid by harvest time. Malolactic fermentation (MLF) can reduce malic and increase lactic by a factor of five.
wine acids con t
Wine Acids (con’t)
  • Citric:Citric acid, minor in grapes but major in many other fruits, is often added to wines to increase acidity or complement a specific flavor. In the grape, citric acid all but disappears during fermentation in much the same way that malic is reduced. It is reduced through normal fermentation and again during MLF.
  • Lactic:Lactic acid is the principal acid found in milk. Grapes contain very little lactic acid. All wines contain some lactic acid, and some wines can contain significant quantities. These wines would be those that had large amounts of malic acid converted by MLF or Malolactic Fermentation.
bad wine acid
Bad Wine Acid !
  • Acetic Acid: Acetic acid is both volatile and odorous, detectable as the smell of vinegar. Very small amounts acetic acid is produced during yeast fermentation and MLF. Vinegar bacteria (acetobacter) convert ethyl alcohol in the wine into acetic acid, and in the presence of air, acetobacter can produce large quantities of acetic acid. Wine is not converted into vinegar when air is excluded, and this is why all winemakers are cautioned to keep their wine containers completely filled and tightly sealed.
why is acid important
Why is acid important?
  • Acids give wines their characteristic crisp, slightly tart taste. Alcohol, sugars, minerals, and other components moderate the sourness of acids and give wines balance.
  • Proper (low 3-3.5) pH in wine is due to the acids producing hydrogen ions in water solutions. The number of hydrogen ions produced can be large or small and it depends on how much acid is present in the solution, and the strength of the acid. Tartaric acid produces 2.7 times more hydrogen ions than an equal quantity of malic acid.
  • The goal is to have just enough acid to produce a balanced wine both in taste and pH for stability.
what is ta and what does mean
What is TA and what does mean?
  • In the United States, titratable acid (total or TA) in wine is expressed in grams of acid per 100 milliliters (percentage) Example 0.55% is 0.55 grams of acid per 100 ml. Note: One hundred milliliters of juice weighs approximately 100 grams so “grams per 100 ml” is roughly equal to percent.
  • Titratable acid is calculated as if all of the different acids in the wine were tartaric acid even though they could be many different acids.
  • The acid content/TA of most finished table wine ranges from 0.55 to 0.85 percent. The desirable acid content depends on style, how much residual sugar is left in the wine and more importantly taste.
how ta is tested
How TA is Tested
  • One of the simplest and most effective ways to measure T.A. in wine/must is by the titration method, which uses an inexpensive titration or acid test kit for $6.50.
  • Accuvin TA Test Kit - The TA Test Kit includes 10 tests, 10 samplers, and an insert with complete how-to-run test instructions. The insert also includes a Summary Interpretation explaining how to use the test results. The label with the color chart is on the front of the kit. Cost $16.00
  • Acidometer - Vinoferm Complete kit to determine the acidity of musts and wines. Contains graduated cylinder, blue indicator solution, litmus paper and complete instructions. Cost $23.00
ta by titration
TA by Titration
  • For most kits, you add a 15 cc sample of strained and or settled wine or must to a plastic cup or small beaker.
  • You then add to the sample 3 drops of phenolphthalein, a pH indicator.
  • You then fill a 10 cc syringe with a titrate solution (usually 0.2N sodium hydroxide).
  • The sodium hydroxide is then added ½ cc at a time to the sample and shaken or swirled.
  • At some point a color change will occur--pink for white wines, gray for red. The amount of titrate solution used is the key to titratable acidity (TA) of the wine. Each cc of solution represents 0.1% TA. Thus, if 5-1/2 cc of solution were used to produce the indicated color change, the TA of the wine or must equals 0.55%.
  • Important that the NaOH is fresh / Buy in small amounts / use caution near eyes.
  • Repeat tests before adjustments will help prevent errors.
ta calculation with ph meter
TA Calculation with pH Meter
  • The titratable acidity of your sample can be determined with the following formula:
  • TA = 75 * V * C/S
  • V = volume of sodium hydroxide needed to obtain a pH of 8.2
  • C = concentration of sodium hydroxide used (0.1 normal or 0.2 normal)
  • S = volume of the sample of wine or must
  • For example: you have a 15ml sample of wine and add 12ml of 0.1 normal sodium hydroxide solution to reach a pH of 8.2. 
  • TA = 75 * 12 * (0.1 / 15)
  • TA = 6 g/L or 0.6 g/ 100 ml = 0.6% 
  • Play with the formula to adjust the sample and the concentration of sodium hydroxide solution. For example; if you use a 15ml sample and the concentration of sodium hydroxide is 0.2 normal, each ml of sodium hydroxide added translates into one gram per liter (0.1 %) of titratable acid.
diluting your sample with water
Diluting your sample with water
  • Color change can be a problem (red wines) so a pH meter can be used and when pH reaches 8.2 then this is your end point.
  • You should start with distilled water which is very clean and usually a neutral (7.0) pH.
  • Using this distilled water will not effect your results but should make the color change easier to see.
increase of ta
Increase of TA
  • Following a proven recipe can take the guess work out and get you close to a specific target before starting fermentation.
  • Acid blend is commonly used to increase the acidity of a must. It usually contains a blend of tartaric, malic and citric acids.
  • Individual acids can be used for a specific purpose.
  • Dosage for an increase of 0.10% TA in 1 gallon:
  • Acid Blend: 3.9 grams
  • Tartaric Acid: 3.7 grams
  • Citric Acid: 3.5 grams
  • 1 tsp of Acid Blend = .12%-.15% in 1 gallon
reduction in ta
Reduction in TA
  • Calcium Carbonate and Potassium Bicarbonate can used to reduce the acidity of wine or must.
  • You should not try to reduce acidity more than 0.3% with either. After using either the wine should be bulk aged and or cold stabilized.
  • Calcium Carbonate: 2.5 grams (~1 tsp) per gallon must lowers TA about 0.1%
  • After its use, the wine should be bulk aged at least 6 months to allow calcium malate, a byproduct of calcium carbonate use, to precipitate from the wine.
  • Potassium Bicarbonate: 3.4 grams (~1 tsp) per gallon must lowers TA about 0.1%
  • When using Potassium Bicarbonate up to 30% of the potential acid reduction occurs during cold stabilization.
acid summery
Acid Summery
  • The tart taste of dry wine or balance of a sweet wine controlled by the total quantity and the kinds of acids present.
  • Tartaric acid is the strongest acid and most stable acid.
  • Measure amount of acid by titration or very simply using Accuvin
  • Avoid adding too much acid to your wine and dilution is the simplest way to reduce it.
  • Calcium Carbonate and Potassium Bicarbonate can used to reduce the acidity of wine or must.
  • TA is the measurement of the amount of acid in a wine and pH is the measurement of the strength of that acid.
sulfur dioxide or so 2
Sulfur Dioxide or SO2

1. What is it?

2. Why is it important?

3. How is it tested?

4. How is it adjusted?

what is sulfur dioxide
What is Sulfur Dioxide
  • Sulphur dioxide, often called sulfite or SO2, has been used in winemaking for over 2000 years.
  • It is used in modern winemaking mainly for its ability to prevent fermentation of unwanted wild yeasts, bacterial action, and its anti-oxidant properties.
  • Molecular SO2 (active) is the most important form of SO2 in wine since it is responsible for the antimicrobial activity.
types of sulfite
Types of Sulfite
  • There are two forms of sulfite typically used in home wine making: Potassium Metabisulfite and Sodium Metabisulfite. Potassium metabisulfite is often referred to as “K-meta” and Sodium Metabisulfite is often referred to as “Na-meta”
  • Sodium metabisulfite= 67.4 % SO2 (Cost is 40-50% less than K-meta)
  • Potassium metabisulfite= 57.6 % SO2
  • There are basically two forms of sulfites which are powder form and campden tablets.
why sulfite is important
Why Sulfite is important
  • Antimicrobial: At low concentrations, SO2 inhibits the development of microorganisms. At high concentrations, it can destroy a proportion of the microbial population. Molecular SO2 is the form responsible for antimicrobial action
  • Antioxidant:SO2 protects both must and wine from excessive oxidation.
  • Fermentation: Prevents wild yeast species from giving you uncontrolled results. Aids in color extraction in grapes and other fruits and also helps prevent browning. It also allows for a greater level of dissolved oxygen in the must (enzymatic oxidation reactions). These higher dissolved oxygen levels provide a healthier environment for the yeast.
free and bound forms of sulfite
Free and Bound forms of Sulfite.
  • Free Sulfite Forms:
  • Molecular SO2
  • Sulfite SO3
  • Bisulphite HSO3
  • Bound Sulfite Forms
  • Unstable Compounds (sugars, uronic acids, ketonic acids, etc.)
  • Stable Compounds (acetaldehyde)
  • Total Sulfite is the combination of the free and bound forms.
  • It is safe to assume that 50% of the total Sulfite added becomes bound and leaves 50% as Free SO2.
molecular so 2
Molecular SO2
  • Molecular SO2 is the principal form of free SO2 that is responsible for anti-microbial activity. The amount of molecular free SO2 available is a direct function of the pH of your must or wine.
  • Molecular SO2 exists as either a gas or as single molecules in juice and wine. It is volatile and is responsible for the odor and sulfurous taste of Sulfite.
  • A good target of the amount of molecular SO2 needed to protect your wine is a level of ~0.8 mg/l.
anti microbial protection
The free sulfur dioxide needed to produce 0.8 milligrams per liter of molecular SO2 for different values of wine pH is shown in the Table.

pH Free SO2

2.8 8

2.9 10

3.0 12

3.1 16

3.2 20

3.3 25

3.4 31

3.5 39

3.6 49

3.7 62

3.8 78

3.9 98

4.0 124

Anti-Microbial Protection
testing free so 2
Testing Free SO2
  • Titrets – Ok for white wines / poor for red wines. They tend to give a result that is approximately 10 to 20ppm too high. 10 tests for $19.00
  • Accuvin Free SO2 Test Kit- The Free SO2 Kit includes 2 High Range Tests (red caps) and 8 Low Range Tests (green caps), 20 samplers, and an insert with complete how-to-run instructions. 10 tests for $18.00.
  • The AO Method – It involves the acidification of a sample, followed by the distillation of SO2 (with air aspiration) out of the sample into a peroxide solution. The acid formed is then titrated with NaOH to an end point, and the volume of NaOH required used to calculate the SO2 level. A simple setup can be put together for less than $50.00.
adjusting so 2
Adjusting SO2
  • The following calculations use the assumption that 50% of the Total SO2 added becomes bound leaving 50% as Free SO2.
  • Campden tablets were originally designed to have a mass of 0.44 grams of potassium or sodium metabisulfite. (Some come in .55g)

One .44 grams K-meta tab = 34 ppm of Free SO2 in 1 gallon

One .55 grams K-meta tab = 42 ppm of Free SO2 in 1 gallon

  • Powder K-meta can be measured by teaspoons or gram scale.

1/8 tsp = .75 grams = 57 ppm of Free SO2 in 1 gallon

Typical extended aging addition to wine kits is ¼ tsp /1.5 grams

¼ tsp = 1.5 grams = 19 ppm of Free SO2 in 6 gallons

10 sulfite solution
10% Sulfite Solution
  • 10% stock solution can be made up by adding enough water to 100 grams of K-meta to make up a total volume of 1 liter (100 grams / 1000 mls * 100 = 10%)
  • Mix two ounces of K-meta with water to obtain a total of 19 fluid ounces and you have a 10% solution. Dilute one part of your 10% solution with 7 parts water, and you have the recommended 1.25% sulfite solution for sanitizing equipment and bottles.
  • One teaspoon of the 10% solution is about 5ml and one tablespoon about 15ml.
  • One ml in one gallon adds 15ppm of Free SO2
lowering so 2
Lowering SO2
  • Blending the high-SO2 wine with another wine low in SO2 is the safest method, ensuring the wine does not suffer from oxidation or further processing.
  • SO2 is often removed from wine by aerating. This is based on the slow oxidation of the SO2 and is only really suitable for slightly excessive doses of SO2.
  • Free SO2 can be removed by adding hydrogen peroxide (H2O2) to wine. Precise measurements and careful additions must be followed.
sulfur dioxide summery
Sulfur Dioxide Summery
  • SO2 is an very important part of successful wine making when used properly and in correct amounts.
  • When testing we are measuring the free or unbound SO2.
  • Molecular SO2 is the principal form of free SO2 that is responsible for anti-microbial activity. The amount of molecular free SO2 available is a direct function of the pH of your must or wine.