Frozen yogurt freezes good bacteria too?

Dear Alice,

If you freeze yogurt does it kill the active cultures, the good bacteria?

Dear Reader,

To answer your question, it may be helpful to start with defining active cultures. The terms “active cultures” and “probiotics” refer to live microorganisms that maintain or improve normal microflora in the body, or the good bacteria as you mention in your question. These live microorganisms can provide immune system support and prevent harmful bacterial growth when taken in the right amounts. Though different species of probiotics are used in food products, the two most common are lactic acid bacteria and bifidobacteria. To make sure that the frozen yogurt you’re buying has probiotics, it’s a good idea to look for the Live and Active Cultures seal on the container or read through the listed ingredients. Although most frozen yogurt contain live probiotic cultures, the extreme temperatures may impact the survival of probiotics.

How well probiotics work in any product can be impacted by food components, process-related factors, and microbiological factors. Ingredients such as sugars, proteins, and fat can affect the growth and survival of active cultures depending on how they interact. Processing methods can also make probiotics more or less viable. For example, while bacteria grow well during the fermentation process, they also tend to die when stored in refrigerators. Finally, it's worth noting that different bacteria have different levels of sensitivity to temperature. Bifidobacteria, for example, are much weaker in colder environments than L. acidophilus. Similarly, higher temperatures lead to increased bacteria metabolism which can harm probiotics.

Keeping these factors in mind, how viable are the probiotics in frozen yogurt? Well, to start, milk may be a key component in keeping active cultures alive. Multiple kinds of milk (including that of cows, sheep, and goats) often used to make frozen yogurt have been found to contain more than 6 log CFU/g (colony-forming units per gram) of probiotics—the minimum amount recommended to observe health benefits. Additionally, while freezing temperatures typically decrease the viability of probiotics in milk products such as ice creams and yogurts, other factors such as microencapsulation (a process that shields the live culture) and ingredients such as sucrose and fat work to protect the live cultures from damage. Since ice cream in particular isn't fermented, when stored correctly, its probiotics can survive for over a year!

While it’s likely that probiotics in yogurt may survive the freezing process, regular yogurt is a more reliable bet when it comes to getting the potential health benefits of good bacteria. That being said, by being an informed shopper and reading labels, you’ll be able to make the best choice (frozen or otherwise) to suit your dietary needs.


Last updated Feb 10, 2023
Originally published May 16, 2014

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