Culturing

Kefir, and what live means on a label

Updated October 2026

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A mixed culture, not a single organism It keeps fermenting in the container Which decides the container Live is a claim worth being careful with No standard of identity means you describe it References

Kefir has no standard of identity and a culture that does not stop, which makes it the most container-dependent product in this property.

A mixed culture, not a single organism

Kefir is fermented by a community of bacteria and yeasts rather than a defined pair, which gives it its character and makes it less predictable. The yeasts are the reason it produces gas and a trace of alcohol, and both of those are packaging problems before they are flavor ones.

It keeps fermenting in the container

Refrigeration slows it and does not stop it, so a sealed bottle continues to acidify and to produce gas on a shelf. That is normal for the product and it means the closure is under load, the product gets sourer over its life, and a warm journey can produce real pressure.

Which decides the container

A closure that can relieve pressure, or a container and fill level that leave room for it, is part of making this product safe to handle rather than a refinement. This is one of the few places in the library where the product can damage its own package.

Live is a claim worth being careful with

Live and active cultures means something specific to buyers and implies the organisms are present and viable at the point of eating, which is a claim about the product at the end of its shelf life rather than at the start. Heat treatment after culturing removes it entirely.

No standard of identity means you describe it

Unlike yogurt there is no composition to meet, so the name is descriptive and the general labeling rules apply. The freedom is real and it also removes the external check, so the pH and the composition become numbers you choose and have to hold.

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 1240.61, Mandatory pasteurization for all milk and milk products in final package form intended for direct human consumption, which prohibits delivering such a product into interstate commerce unless it has been pasteurized or is made from pasteurized dairy ingredients. 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.