U.S. Food and Drug Administration
Center for Food Safety & Applied Nutrition

pH Control--Why the Concern?


This booklet explains why the food processing employee must be concerned with properly controlling the acidification and determining the pH of foods. It covers these subjects in three sections:

  1. "The Importance of pH in Acidified Food Processing"

    Defines pH in non-technical language, alerts employee to problems of inadequate pH control, and, finally, stresses the key role the employee plays in helping to assure the production of safe, quality foods.

  2. "Regulatory and Technical Information on Acidified Foods"

    Summarizes pertinent FDA regulations and information pertaining to the processing of acidified foods.

  3. "pH Measurement Precautions"

    Contains a list of specific reminders to consider when taking pH measurements.

The Importance of pH in Acidified Food Processing

You've Read About it in the Papers, You've Seen it on TV

You know the stories to which we are referring. That's right, the ones about companies having to recall their food products.

Some plant have been forced to cease distribution of their acidified foods in interstate commerce because of poor pH control of their acidified products.

What Do these Problems Have to Do with You?

The answer is PLENTY if you work with foods that have to be acidified.

You can, if you are not careful, make the same mistakes as those plants.

If you do, the foods your plant produces will have to be recalled.

What is pH?

The pH of a food is the measure of that product's acidity or alkalinity.

Your taste can recognize major differences in the pH of various foods. An acid product would taste sour. An alkaline product would taste bitter.

This range in flavor is due to what is called the hydrogen ion concentration on the food.

The more hydrogen ions present, the more acid the food and the lower the pH.

If your company processes foods the same as, or similar to those illustrated, extra care must be exercised to maintain their appropriate pH.

Inadequate control of the pH can result in the growth of undesirable bacteria in the product that could be a potential health hazard to an unsuspecting consumer.

You wouldn't want your firm's customer's to eat a toxic product.

What Can You Do?

You must see to it that all of the critical requirements for the manufacture and processing of your firm's foods are followed.

Regulatory & Technical Information About Acidified Foods

Acidified Foods

The Federal Regulation define acidified foods as those low-acid foods which have had their pH reduced to 4.6 or lower by the addition of acids or acid foods. Vinegar or any safe and suitable organic acid or acid food can be used for this purpose.


Acidification is one means of preserving food products. In addition tob preventing bacteria growth, acidification helps maintain a desired product quality. Puddings, cucumbers, artichokes, cauliflower, peppers and fish are examples of low-acid foods which are normally acidified.

The addition of an acid or an acid food to such products s a method of preservation which is designed to prevnet bacteria of public health significance from growing. If acidification is not adequately controlled at a pH of 4.6 or below, Clostridium botulinum, a toxin-producing micro-organism, can grow in the food.

Clostridium Botulinum

C. botulinum is almost universally present. It is capable of producing a potent toxin which affects the nervous system. A person who has consumed this toxin will become extremely ill and may even die.

C. botulinum will grow and produce this toxin in foods which are packaged in the absence of oxygen, have a favorable pH and temperature, and contain water and nutrients necessary for its growth. Low-acid canned foods provide this favorable environment.

When a product is acidified to a pH of 4.6 o less, according to the Good Manufacturing Practices, inhibition of the growth of C. botulinum is assured.

Personnel Qualifications

All operating personnel concerned with the acidification of foods must be under the supervision of a person who has attended a school approved by the Commissioner of the Food and Drug Administration. This school will have presented instructions of pH and the critical factors to be considered in the acidification of foods.

pH Measurement Precautions

When you measure the pH of your company's raw materials, in-process goods, or finished products, you should take the following precautions:

"Your Control of Acidification & pH
Makes the Difference in the Safety of your Company's Product.
This Can Mean your Job, Too!"

Additional Information on Acidified Foods, Low-Acid Canned Foods, and General Food Regulations

Current Good Manufacturing Practice (GMP) in Manufacturing, Processing, Packing or Holding of Human Foods (21 CFR Part 110).

Emergency Permit Controls and Current Good Manufacturing Practices for Acidified Foods and Low-Acid Canned Foods in Hermetically Sealed Containers (21 CFR Parts 108, 113 & 114).

Single copies of these publications are available free of charge from:

Industry Activities Staff (HFS-565)
Food and Drug Administration
200 C Street SW
Washington, DC. 20204

To expedite shipment, please include a self-addressed mailing label.

Establishments engaged in the manufacture of Low-Acid or Acidified Canned Foods (LACF) offered for interstate commerce in the United States are required by 21 CFR Parts 108, 113, and 114 to register their facility with form FDA 2541 and file scheduled processes for their products with forms FDA 2541a , "Food Process Filing for all Methods Except Low-Acid Aseptic", and FDA 2541c, "Process Filing for Low-Acid Aseptic Systems."
The forms and instructions are available by:

LACF Registration Coordinator
200 C St. SW
Washington, DC 20204

TELEPHONING: 202-205-5282

FACSIMILE: 202-205-4758 or 202-205-4128


(Please type or print clearly)

Please forward the following forms and/or publications:

___ea. FDA 2541. Food Canning Establishment Registration

___ea. FDA 2541a, "Food Process Filing for all Methods Except Low-Acid Aseptic"

___ea. FDA 2541c, "Process Filing for Low-Acid Aseptic Systems"

___ea. "Instruction for Establishment registration and process filing for acidified and low-acid Canned Foods"

___ea. "Aseptic Packaging Systems Supplement to Instructions for Establishment Registration and Process Filing for Acidification and Low-Acid Canned Foods"

___ea. "Instructions for Estabblishment Registration, Thermal Process Filing, and Good Manufacturing Practices for Low-acid Canned and Acidified Foods". Title 21 CFR Parts 108, 113, and 114.



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