Happy Cheese Makers Since 1978

How To Test For Acid

Why is it important to test for acid?

When we are trying to convert the lactose in cheese to lactic acid by using a culture, there is no visible way to determine to what extent the culture is working.
Tracking acidity development is one of the surest ways to know about the activity of your culture and to tell if it is doing the work it was intended to do

What is required for equipment?

There is actually very minimal equipment needed for this simple test.
We provide 2 options on our web site:

Our Acid Testing Kit

    You can easily test the acidity of milk, cheese whey, and other dairy products with our inexpensive acid testing kit. Increasing acidity levels are an important part of cheese making and this kit takes away the guess work.

    This kit is suggested for the home cheese maker who will use it only occasionally

Our Acidimeter

    These burettes make taking titration readings a snap. Small screw clamp lets you preset drop speed for repeat titration and a quick squeeze of the bottle will refill the burette to the zero point.

    We suggest this apparatus for the serious home cheese maker and farmstead cheese makers who will be making these tests on a much more frequent basis

How to we do this test?

Directions for using the Acidimeter or Acid testing Kit (depending on which setup you are using)

  1. If using the Acidimeter fill the glass reservoir with .1N NaOH (Sodium Hydroxide Solution)
  2. If using Acidimeter fill the graduated column with the NaOH by applying pressure to the rubber pump. It will go to zero with any excess draining back into the reservoir
    if using 'Acid Testing Kit' fill the provided syringe with 3 ml of .1N NaOH.
  3. Now using a syringe or a pipette, measure 9 ml of milk
  4. Pour this sample into a test tube or a beaker (preferably held against white surface)
  5. Add 5 drops of phenolphthalein to the milk sample and stir gently
  6. Open the tap (stopcock) or use syringe to let the NaOH run drop by drop into the sample while stirring gently

    before stirring
    keep adding NaOH
    stop adding NaOH
    this is the final color
  7. Continue until the appearance of a light pink coloring which persists for 10-20 seconds
  8. Look on the column or syringe to see how many ml of NaOH were used
    .. multiply this by .1 (move decimal point 1place left) for the actual TA%

    Example: If the amount of NaOH used is 1.6ml then the titrateable acidity is .16 %

    Some books may refer to Dornic acid degrees ... This is simply done by moving your column reading one place to the right ... i.e. graduation is 1.6 = 16 Dornic degrees.

    Note: The life of Sodium Hydroxide Solution : approximately 1 year in a sealed bottle