A measure of acidity or alkalinity that, alongside water activity, determines whether a food supports the growth of pathogens.
A measure of acidity or alkalinity that, alongside water activity, determines whether a food supports the growth of pathogens. pH is a measure of how acidic or alkaline a food is, on a scale from 0 to 14, where 7 is neutral, lower values are more acidic and higher values are more alkaline. The acidity of a food strongly affects whether harmful microorganisms can grow in it, which makes pH an important factor in food safety and preservation. Most foodborne bacterial pathogens grow best around neutral pH and are inhibited as conditions become more acidic. A pH of 4.6 or below is a widely used threshold, because below it the growth of many dangerous bacteria, including the organism that causes botulism, is controlled. Acidification, fermentation and pickling all work by lowering pH to make foods safer and more stable. For a food business, pH is used together with water activity to decide whether a food is potentially hazardous and to validate acidified or fermented products. Products such as pickles, sauces, fermented vegetables and some dairy rely on reaching and holding a target pH to be safe, and getting this wrong can allow dangerous toxins to form. Businesses making such products typically measure pH with a calibrated pH meter and record results as part of their food safety program, confirming each batch reaches the validated limit within the required time. Under the Food Standards Code, showing that pH and water activity prevent pathogen growth or toxin production can take a food outside the potentially hazardous food definition. A producer bottling a chilli sauce ferments and acidifies the product until it reaches a pH of 4.2, measures each batch with a calibrated pH meter, records the reading against the 4.6 threshold in its food safety program, and uses that evidence to sell the sauce as a shelf stable product.
Frequently asked questions
What does pH measure?
pH measures how acidic or alkaline a food is on a scale from 0 to 14, where 7 is neutral, lower is more acidic and higher is more alkaline.
Why is pH 4.6 an important threshold?
At or below pH 4.6 the growth of many dangerous bacteria, including the organism that causes botulism, is controlled, which is why acidified foods target this level.
How does pH relate to food safety?
Acidic conditions inhibit most foodborne pathogens, so pH is used with water activity to judge whether a food is potentially hazardous and to validate preserved products.
How is pH measured in a food business?
It is measured with a calibrated pH meter, and results are recorded as part of the food safety program to show each batch met its validated limit.
Can a low pH make a food shelf stable?
A sufficiently low pH, often combined with low water activity, can prevent pathogen growth and allow a food to be stored safely at ambient temperature.
