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How can I determine the acidity of my vinegar myself?

02. 02. 2020

General information on the production of vinegar

As mentioned in my last post, constant control of some parameters is required in order to make high quality vinegar.

In addition to the temperature and the oxygen supply, the development of the acetic acid content in the so-called mash should be monitored repeatedly. While the temperature can be checked relatively easily with the appropriate digital thermometers, determining the acid content is somewhat more complex.

In the following instructions I explain how you can determine the acidity of vinegar yourself.

You should consider the following basic requirements right from the start:

The determination of the acid content is a chemical analysis method that requires particular caution.

The chemicals that are used are harmful to humans in some way. It is therefore necessary to observe the general and special laboratory rules and to take preventive protective measures.

The analytical method with which you can determine the acidity of the vinegar yourself is called Titration or Dimensional analysis. The acidity of the vinegar is calculated by using a so-called standard solution with a known concentration. Normally, 1 molar sodium hydroxide solution is used as the standard solution.

This analytical method requires the phenolphthalein indicator to be used with particular care. Phenolphthalein is a so-called pH indicator that changes its color depending on the pH value of the liquid. In the acidic and neutral range (pH value from 0 to 8.2) this indicator is colorless. From a pH value of 8.2, the color changes from colorless to pink. This indicator is therefore well suited for the titration of weak acids with strong alkalis, because the equivalence point here is also in the alkaline range. The equivalence point is the point at which a certain amount of acid has been neutralized with the corresponding amount of base.

What you need to determine acetic acid:

Equipment

• Safety goggles

• burette

• 10 ml pipette

• 250 ml Erlenmeyer flask

• Peleus ball

• Magnetic stirrer

• Magnetic stir bars

Chemicals

• Phenolphthalein

• Sodium hydroxide standard solution (1 mol / l)

• Distilled water

Measuring process

Since the measuring devices used are calibrated to a temperature of 20 ° C, all chemicals used and also the vinegar must be heated or cooled to a temperature of 20 ° C.

Since sediment or other suspended matter can form during the fermentation of vinegar, the vinegar should be filtered before analysis. In the simplest case, this can be done with a coffee filter.

The Peleus ball or another pipetting aid is now placed on the volumetric pipette.

Before starting the analysis, the cleaned and dry volumetric pipette is filled with vinegar up to the marking ring with vinegar and then emptied again. This allows any residues of water or the like to be removed.

With the “neutralized” volumetric pipette in this way, exactly 10 ml of the filtered, 20 ° C warm vinegar is placed in the Erlenmeyer flask. After the vinegar has been placed in the flask, the Erlenmeyer flask is filled with distilled water to approximately the 100 ml mark. Now three to four drops of phenolphthalein are added to the Erlenmeyer flask.

Now the Erlenmeyer flask with the diluted vinegar and the indicator is placed on the magnetic stirrer and a magnetic stir bar is added. The magnetic stirrer with the magnetic stir bar ensures that the vinegar is constantly mixed.

After switching on the magnetic stirrer, the standard solution of sodium hydroxide solution (1 mol / l) is added drop by drop with the burette to the diluted vinegar. This process is carried out until the liquid in the Erlenmeyer flask turns pink in the area where the drop is immersed in the liquid. From this point on, the standard solution must be added even more carefully.

The short video shows the course of the titration up to the point of transition.

The so-called equivalence point is reached when all of the liquid in the Erlenmeyer flask turns pale pink for about one minute. Now no more custom-made solution may be added. The consumption of the standard solution is now read on the burette.

Evaluation example

Consumption of standard solution of sodium hydroxide solution (1 mol / l) = 8.7 ml

Acetic acid content = 8.7 * 0.6 = 5.22%

With this simple analysis method you can determine the acidity of the vinegar you produce yourself.

For more information on how to carry out the analysis, to sources of supply of Equipment racks and from chemicals as well as too simple Evaluation programs I am happy to help.

Simply write us an email to: [email protected]

Also visit the website with our fruity fruit vinegars. Under the link Fruit vinegars learn more about our homemade vinegars made from fruit and herbs.