Acidity testing - analysis
TA (titratable acidity)
Titratable acidity (abbreviated as TA) is an approximation of the Total Acidity of a solution and constists of organic acids (tartaric, malic, and citric)
TA = 75 x NaOH molarity x (NaOH titrated ml / Wine sample ml)
Example:
TA = 75 x 0.1 x (4ml/5ml)
TA = 6 g/l
- The optimal TA should be somewhere between 6-9 g/l
VA (Volatile acidity)
VA consists of primarily acetic acids which mean - vinegar spoilage. This is a bit more complicated process where steam distillation is required. You can do the test for acetic acid concentration twice - right after the fermentation and then after storing (2 weeks and later). However, the biggest probability of wine spoilage is just during the process of storing.
You will need sodium hydroxide (0.1N), phenolphthalein (1%), and hydrogen peroxide 0.3%. Prepare 10-15 ml of wine and add 1-2 drops of hydrogen peroxide. Distill the solution (it will take cca 15-30 min). After take 10 ml of the distill and repeat the titration process above. Add 3 drops of phenolphthalein. Get the NaOH into 5 ml syringe and drop by drop drip the solution to the sample (wine with phenolphthalein). At the same time, do round movement/shake gently with the sample - keep stirring up. Drip NaOH as long as the color indication keeps disappearing. Once the sample stays colored, count the ml of titrated NaOH and use the number for calculation formula:
VA = titrated NaOH x 0.6 (if NaOH molarity is 0.1N and if the sample of distill is 10ml)
or
VA= (titrated NaOH x NaOH molarity) x 0.06 x (1000 / sample of distill ml)
Example:
VA = 1ml x 0.6
VA= 0.6 g/l
or
VA= (1 x 0.1) x 0.06 x (1000 / 10ml)
VA= 0.6 g/l
- The optimal VA during fermentation is 0.2-0.4 g/l and later after storing between 0.6-0.9 g/l - if the values are higher, you can use it as vinegar for a salad :)
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