pH is a measure of how acidic or alkaline an aqueous solution is. The scale is logarithmic: a lower pH indicates greater acidity, a higher pH indicates greater alkalinity, and pH 7 is neutral at approximately 25°C. In food preparation and food safety, pH influences flavour, colour, texture, enzyme activity, microbial growth and the effectiveness of some preservation processes.
Because the scale is logarithmic, a change of one pH unit represents a tenfold change in hydrogen-ion activity. The pH of foods varies with ingredient, variety, ripeness, formulation and processing.
Acidity can change the colour of vegetables and pigments, affect the softening of plant tissues, influence protein behaviour and provide brightness in sauces and dressings. Alkaline conditions can alter browning, texture and the behaviour of some ingredients, as seen in pretzel preparation and certain noodle styles.
Acidity can restrict the growth of some microorganisms, but pH alone does not prove that a food is safe. A pH of 4.6 or below is an important regulatory boundary used in controlling the growth of Clostridium botulinum in certain acidified and low-acid canned foods. It does not mean that all pathogens are destroyed or that an unvalidated recipe is shelf-stable. Food safety also depends on water activity, heat treatment, packaging, formulation and storage conditions.
Use a suitable, calibrated pH meter or appropriate test method, following the instrument and process instructions. Take representative samples and record results when pH is part of a validated recipe or food-safety control. Do not rely on taste to estimate pH.
Chef’s tip: When developing pickles, sauces or preserves, use a tested formulation and calibrated measurement method. Adjusting acidity by taste alone is not a reliable safety control.
This term is one of hundreds covered in depth across OCS courses, learning paths, and 1-on-1 coaching with Chef Eric.
