Low-acid canned foods and acidified foods: the pH 4.6 line

The three classes

• Acid foods have a natural pH of 4.6 or below¹. A tomato is an acid food.
• Acidified foods are low-acid foods with acid or acid foods added, with a water activity above 0.85 and a finished equilibrium pH of 4.6 or below¹. Cucumbers made into pickles with vinegar are acidified, and so are most hot sauces, barbecue sauces, salsas and vinaigrettes.
• Low-acid foods have a finished equilibrium pH above 4.6 and a water activity above 0.85, alcoholic beverages aside². Plain green beans, most soups, bone broth, most dips and queso-style products fall here.

Water activity measures free moisture: the closer to zero, the less is available, and pure water is 1.00³. Tomatoes and tomato products with a finished equilibrium pH below 4.7 are not classed as low-acid².

Low-acid canned foods

A low-acid canned food is a low-acid food packed in a hermetically sealed container, meaning one designed and intended to be secure against the entry of microorganisms. It has to be made commercially sterile: free of microorganisms that can reproduce in normal storage without refrigeration, and free of viable pathogens. The scheduled process that gets it there must be at least equivalent to one established by a competent processing authority².

The plant registers the establishment with FDA and files each process. Acidified foods are filed on Form FDA 2541e, and low-acid canned foods on Form FDA 2541d, 2541f or 2541g⁴.

What is not an acidified food

FDA's acidified definition leaves out carbonated beverages; jams, jellies and preserves; acid foods with small amounts of low-acid ingredients that keep a similar pH; and foods stored, distributed and sold under refrigeration¹.

What each class means for your co-packer

An acidified food needs a scheduled process from a process authority. The plant registers with FDA and files that process for each product in each container size before it packs the product⁵⁶. Production has to be supervised by someone who completed an approved course, such as Better Process Control School³⁶.

A shelf-stable low-acid food has to be made commercially sterile under FDA's low-acid canned food rule, with a process at least equivalent to one set by a competent processing authority². That means retort or aseptic processing, which far fewer plants run.

Of the 245 plants in this directory, 9 state retort and 11 state aseptic processing, against 50 that state hot fill. 13 say outright that they make acidified foods under 21 CFR 114.

Change the recipe and the process may change too. Washington's agriculture department lists changing an acidified recipe without having it re-evaluated among the most common acidified food violations³.

Why sauce founders meet this first

Cornell's Food Venture Center notes that low-acid and acidified foods cannot be made in home kitchens⁷. That is one reason sauce, salsa and soup founders need a licensed kitchen or a co-packer early.

Sources

1. 21 CFR 114.3, definitions for acidified foods (Cornell LII) (Government)
2. 21 CFR 113.3, definitions for low-acid canned foods (Cornell LII) (Government)
3. Washington State Department of Agriculture, Industry Guidance: Acidified Foods (Government)
4. FDA, Establishment Registration and Process Filing for Acidified and Low-Acid Canned Foods (Government)
5. 21 CFR 108.25, acidified food registration and process filing (Cornell LII) (Government)
6. NC State Extension, Resources and Steps for Acidified Processors (University)
7. Cornell Food Venture Center, Kitchens and Co-Packers (University)