Virginia Food Processor Technical Assistance Program

What is pH?

pH is a unit of measurement used to express the degree of acidity of a product. The pH scale runs from 0 meaning very acidic to 14 which is very basic. You can actually taste the difference in many cases. An acid food will taste very sour while a basic (alkaline) food will taste bitter. Here is a pH scale example:

From pH 0-6 is acidic, from pH 8-14 is basic, and pH 7 is neutral, between the two extremes, so it is neither acidic nor basic (alkaline).

The scale is actually referring to the concentration of hydrogen (H+) ions in the product being tested. The more H+ ions that are present, the more acidic the product will be. The scale is logarithmic, meaning that each pH unit has 10 times more H+ ions than the one above it.

pH is very important in many different areas, food being one of them. Many products must be produced at certain pH values to ensure a good quality product. For example, if the pH is off, curd size will vary in cottage cheese or jelly will not properly gel. pH can cause drastic changes in a food product. It is also very important for learning whether or not the product is an acidified food, which requires special regulation and processing.

When measuring the pH with a pH meter, precautions should be taken when analyzing a product.

1. Follow the manufacturer's instruction manual.

2. Standardize the pH meter with a buffer solution.

3. Follow the accepted procedure for pH measurement.

4. Prepare the sample as described.

5. Maintain the pH meter in good condition and working order.

6. If you have any questions, contact your supervisor.

One tool for measuring pH is the pH meter. It works by measuring the voltage caused by the H+ ions in the product. An electrode is dipped into a solution containing the product and a value will appear that gives you the pH value of the product being tested.

Before testing remember to calibrate the pH meter! Without this step the pH measurement could be way off and give a false reading. Here's how to calibrate your pH meter:

1. Take the electrode and connect it to the meter
2. Remove storage vessel and rinse electrode with distilled water
3. Dab the electrode with a soft paper, do NOT rub.
4. Dip the electrode into buffer pH=7 making sure that the whole end (probe) is immersed in the buffer.
5. Start the calibration on the meter.
6. Rinse and begin again with pH=4 and repeat.

 

Links

Approximate pH of Foods & Food Products (FDA)

Includes an extensive list of food items and their approximate pH values.

Choosing & using a pH meter for food products (Oklahoma State University- FAPC)

Information on choosing a pH meter suitable to your needs, resolution and accuracy of the meter, probe features, calibration, preparing of food samples prior to testing, and cleaning of the meter.