Cider vinegar titration to ascertain it’s suitability for pickling raw fish.

As alluded to in a previous post I would like to use my wildcrafted cider vinegar to pickle raw fish, as in herring rollmops. In order to do so free from the risk of botulism the vinegar must contain at least 5% acetic acid. I purchased a Ritchie’s brand, wine and beer titration kit. It cost about £8. The instructions provided are used for wine and will test for sulphuric acid whereas I want to test cider vinegar for acetic acid.
Below i’ll describe the few, simple processes I went through to do so.
The kit contains: 2.5ml syringe (labelled as 2ml, but graduated up to 2.5ml), 114ml sodium hydroxide, 28ml acid indicator solution, standard sized test tube (roughly 23ml capacity).
I didn’t think the test tube would be large enough so I used a regular drinking glass.
IMG_0198
1. To the glass I added 2 ml vinegar.
When filling the syringe I made sure to line up the fluid at eye level, by lining up the black line on the outside of the jar with the bottom of the stopper. I’ve noticed that it’s quite easy to rub the black lines out on the syringe. They’re probably only made to be used once and discarded.
2. Added 20 ml water from the tap.
3. Added 3 drops of indicator solution. Easy because the bottle has a dropper on it.
4. Added 1.5ml of standard base, drop by drop, swirling with right hand, dropping with left. Each drop turns it a little pink till you mix it in. It turned completely pink after 1.5ml.

IMG_0200

Adding the standard base drop by drop whilst swirling the glass.

Finished the titration, now for the calculation.

Finished the titration, now for the calculation.

So:
1.5ml  x 0.6 = 0.9% acetic acid. Not enough for pickling raw fish then.

Next step: i’ll leave the vinegar longer to see if more acetic acid will form, then test again in a couple of weeks or more.

This is a copy/paste from the link I got my info from.

Vinegar Titration Procedure

    1. With the 10 ml syringe, measure out and add to the test container 2.0 ml of homemade vinegar. Then clean out the syringe.
    2. With the 20 ml syringe, add 20 ml of water to the test container.
    3. Add 3 drops of indicator solution to the test container.
    4. Fill the cleaned 10 ml syringe to the 10 ml mark with the standard base.
      Dispense the standard base solution slowly into the test container one drop at a time. As you add the base, gently swirl the test container to continuously mix its contents, and stop adding base when the vinegar solution turns pink.
    5. When the sample has changed color, note the amount of base solution used in the 10 ml syringe.
      • (If you started at 10 ml in the syringe and finished at 1.6 ml then the amount of base used would be: 10.0 – 1.6 = 8.4 ml.)
    6. Calculate the % acetic acid in the vinegar sample by multiplying the volume of base used by 0.6.

Example:

      If 8.4 ml of standard base was used to titrate the vinegar sample then the amount of acetic acid in the sample would be: 8.4 x 0.6 = 5.0%
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