Culturing

Yogurt, and the number you already know

Updated October 2026

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What the standard requires The 2021 amendment made the connection explicit Within 24 hours after filling matters Which makes a pH meter non-negotiable Call it something else if it does not meet the standard Lowfat and nonfat are separate provisions References

The yogurt standard of identity carries the same 4.6 that defines an acidified food, in a product nobody calls acidified, for exactly the same reason.

What the standard requires

Not less than 3.25 percent milkfat, not less than 8.25 percent milk solids not fat, and a pH of 4.6 or lower measured on the finished product within 24 hours after filling. Lowfat and nonfat versions are provided for separately with their own fat limits.

The 2021 amendment made the connection explicit

The requirement used to be expressed as titratable acidity. It is now a pH, and the figure chosen is the same one the acidified foods definition turns on. That is not a coincidence; 4.6 is the practical line below which the organism of greatest concern does not grow, and it does the same work in a yogurt that it does in a pickle.

Within 24 hours after filling matters

The measurement is specified on the finished product within a window, which means the fermentation has to be far enough along at the point of filling that it reaches the number in the container. Filling early and hoping is how a batch ends up out of specification with no way back.

Which makes a pH meter non-negotiable

You cannot taste 4.6, and a product at 4.8 tastes like yogurt. The meter is the cheapest item on the equipment list and the one that tells you whether you made the product the label says you made.

Call it something else if it does not meet the standard

A cultured milk product outside those numbers is a legitimate product that may not be called yogurt. That is the same mechanism as the syrup and peanut butter standards, and the same honest answer applies: name it for what it is.

Lowfat and nonfat are separate provisions

The standard provides for them with their own milkfat limits, so a reduced-fat product is not simply yogurt with less fat, it is a differently named standardized food. Getting that wrong is a labeling error rather than a production one, and it is easy to make.

References

21 CFR 131.200, Yogurt: not less than 3.25 percent milkfat and not less than 8.25 percent milk solids not fat, with “a pH of 4.6 or lower measured on the finished product within 24 hours after filling.” law.cornell.edu

21 CFR 114, Acidified Foods, whose 114.3 definition turns on a finished equilibrium pH of 4.6 or below, the same figure the yogurt standard uses. law.cornell.edu

Written from federal regulation and FDA guidance, not from a laboratory. Pasteurization of milk and milk products in final package form for interstate commerce is a federal requirement, and what your state permits inside its own borders is a separate question. Anything here is a starting point for a conversation with your state department of agriculture, not a determination that you comply.