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Measuring Titratable Acidity in Wine

Measuring Titratable Acidity in Wine or Grape Juice. The acids in wine are an important component in both winemaking and the finished product of wine. They are present in both grapes and wines, having direct influences on the color, balance and taste of the wine as well as the growth and vitality of yeasts during fermentation and protecting the wine from bacteria. One of the measurements of acidity in wine is known as the "Titratable Acidity" , sometimes called "Total acidity", which refers to the amount of tartaric acid present in g/L, while strength of acidity is measured according to pH with most wines having a pH between 2.9--3.9. Generally, the lower the pH, the higher the acidity in the wine. However, there is no direct connection between titratable acidity and pH (it is possible to find wines with a high pH for wine and high acidity) The titratable acidity or TA of wine or must is determined by titration of a sample with a standardized solution of sodium hydroxide (NaOH) The following equipment will be needed to measure the TA of a wine or must sample: Equipment: 250 ml erlenmeyer flask 5 ml volumetric pipet -- Class A Hot Plate 10 or 25 ml buret Pipet Safety Bulb or Syringe Supplies: 0.10 N NaOH Phenolphthalein w/dropper Distilled Water 5 ml wine/juice sample Pipet 5 ml of wine or juice must into an Erlenmeyer flask. Add approximately 2 ml of DI water to cover the bottom of the flask with liquid and add 3 drops of 1% Phenolphthalein. Note: juice or must samples may need to be strained or centrifuged before pipetting. Fermenting wine samples should be degassed prior to obtaining the test sample. Using either a Digital Titrator fitted with a .1 N Sodium hydroxide bottle, or a prepared 25ml burette with .1 N Sodium hydroxide, titrate the Erlenmeyer flask sample to a pink endpoint. Measure the pH of the sample as you near the end point of the titration. The pH reading at the endpoint should read 8.2 Continue titration until an 8.2 pH endpoint is achieved. The Titratable Acidity is calculated using the following formula: TA (as g Tartaric/100ml sample) = (ml NaOH) (N NaOH) (1.5) Example: (6.0 ml NaOH)(.1N NaOH)(1.5) = .900 g Tartaric Record your findings. Samples may be disposed of in the sink and rinsed thoroughly with water. Lab ware should be washed with and rinsed with DI water.