Introduction to Acid Foods
What are Acid Foods?
Acid Foods: A food with a natural pH of ≤4.6. There are many naturally acidic foods, including apples, yogurt, peaches, onions, tomatoes, strawberries and lemons.
"Acid Foods" as a general group are not regulated, although certain sub-groups of acid foods are.
Types of Acid Foods
There are two main types of acid foods
Acidified Food: These are low-acid foods that has been acidified by adding something acidic so that the end product is ultimately acidic has an equilibrium pH of ≤4.6) . This includes foods such as: dill pickles, hot sauce, and pickled fish.
The FDA does not include the following to be Acidified Foods:
Jams, jellies & preserves
Naturally acid foods like peaches and most fruit juices
Foods with a water activity of ≤0.85
Foods which are stored under refrigeration
Fermented foods (i.e. kimchi, sauerkraut, natto)
The FDA regulates acidified foods in 21 CFR Part 114.
Formulated Acid Foods: These are composed mostly of acid foods to which a small amount of low-acid ingredients are added (generally less than 10% by weight). The low proportion of low-acid ingredients means that the pH doesn't change significantly from the pH of the dominant ingredients. Examples include:
Is my product an Acidified Food?
Consider this flow chart to determine if your product is regulated by the FDA as an Acidified Food:
Click to enlarge
What's the difference between an acidified food and a formulated acid food?
The difference between these two types acid foods depends on the proportion of low acid and high-acid ingredients in each product:
Acidified foods are typically low acid foods with an added acid (which acidifies the low acid food.)
Formulated Acid foods are composed mainly of high acid foods with a small amount of low acid foods added.
Formulated Acid Foods
In order to qualify as a "formulated acid food", the low-acid ingredients must not significantly shift the pH of the product from the natural pH of the high-acid ingredients.
For a food product whose equilibrium (final) pH is <4.0, then a shift of up to 0.4 is considered insignificant.
For a food product whose equilibrium (final) pH is >4.0, then a shift of up to 0.1 is considered insignificant.:
Example #1: Ned's BBQ Sauce.
Ingredients by weight: Tomato paste (93%), Sugar (5%), Spices (2%)
Ned's BBQ Sauce Equilibrium pH: 3.9
pH of only High-Acid Ingredients: 3.6
Change between high-acid ingredients and final product = 0.3
Since the equilibrium pH of Ned's BBQ Sauce is below 4.0, only an increase of 0.4 or more would be considered significant. Since the low-acid ingredients only increase the pH by 0.3, this change is considered insignificant.
Outcome: Ned's BBQ Sauce is a Formulated Acid Food. It is not subject to 21CFR Part 114
Example #2: Ned's Marinade
Ingredients by weight: Tomatoes (60%) Onion (10%) Vinegar (20%) Sugar (7%) Spices (3%)
Ned's Marinade Equilibrium pH: 4.2
pH of only High-Acid Ingredients: 4.0
Change between high-acid ingredients and final product = 0.2
Since the equilibrium pH of Ned's BBQ Sauce is above 4.0, an increase of above 0.1 would be considered significant. Since the low-acid ingredients increase the pH by 0.2, this change is considered significant.
Outcome: Ned's BBQ Sauce is an acidified food. As a result, it is subject to The regulations in 21 CFR Part 114.