Does Freezing Yogurt Kill Probiotics? (Answered!)

Probiotic bacteria in yogurt are able to survive freezing for a approximately 4-6 weeks. Freezing will put the probiotic bacteria in a dormant state and when they are eaten and return body temperature they will reactivate. There can be over 10 million live bacteria in every gram of frozen yogurt.

An article published in the Journal of Dairy Science, showed that when frozen strains of probiotic bacteria including Streptococcus salivarius ssp. Thermophilus, Lactobacillus delbrueckii ssp. Bulgaricus Bifidobacterium longum and Lactobacillus acidophilus did not decrease¹.

This article will explore more about what happens to the probiotic bacteria when you freeze yogurt.

Yogurt and probiotics

For the food to be classified as a yogurt and labelled with “contains live and active cultures”   the U.S. Food and Drug Administration (FDA) state that it must contain “a minimum level of live and active cultures of 10⁷ colony forming units per gram (CFU/g)”².

The FDA also state that yogurt must contain the lactic acid-producing bacteria, Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus². Manufacturers can also add other bacteria such as L. acidophilus and Bifidobacteria

These bacteria survive frozen or refrigerated. These bacteria are essential to process of making yogurt. Bacteria will ferment and break down the lactose in milk which creates acid giving yogurt its sour taste.

Is it safe to freeze yogurt?

You can extend the shelf life of yogurt by freezing it. According to the USDA:

“Yogurt can be stored in the refrigerator (40 ºF) one to two weeks or frozen (0 ºF) for one to two months”³.

Yogurt can last for around 4 weeks at or below fridge temperatures of 40 degrees Fahrenheit while in the freezer it can last for 1-2 months³.

Freezing the yogurt will not kill probiotic bacteria but will instead put it into a dormant state. The bacteria will ‘wake up’ when you eat the yogurt and the temperature rises.

According to the Harvard Medical School, probiotic bacteria can then act in your gut to help to break down and release nutrients for your body helping with digestion and gut health⁴.

How to Freeze yogurt

You can flash freeze yogurt to conserve as much bacteria as possible. Dropping the temperature as fast as possible down to freezing will avoid killing the bacteria but will instead put them in a dormant state.

Here are the easy steps to rapidly freeze yogurt and avoid killing bacteria.

1. Place yogurt in a glass or plastic container
2. Cover the yogurt with an airtight lid (leave around ¼ an inch of space
3. Place the yogurt in a bowl of ice with added salt and water
4. Allow the yogurt to sit in the bowl for around 10 minutes
5. Transfer the yogurt into your freezer.

Rapidly cooling the yogurt in this way will help to conserve as many probiotic bacteria as possible.

You can also place the yogurt straight into your freezer in an airtight container. This will still rapidly cool the yogurt conserving most of the bacteria.

How to thaw frozen yogurt

Frozen yogurt should be thawed in your fridge to conserve the bacteria and keep the yogurt at a temperature that is safe to eat. Take the yogurt out of the freezer and place it in your fridge 24 hours before you want to eat it.

Freezing probiotic yogurt – FAQs

Does freezing damage probiotics?

Freezing does not damage probiotics but over a period of time their numbers will decrease. Freezing yogurt will conserve the bacteria for anywhere between 4-6 weeks. After this period of time there will be less probiotic bacteria surviving in your frozen yogurt.

What happens if I freeze yogurt?

Yogurt can be frozen which will conserve the probiotic bacteria. Frozen yogurt will taste less sweet than when it is at fridge temperatures so there is often more sugar or sugar alternatives added to frozen yogurt products.

The yogurt can split as it defrosts leaving a liquid whey layer on top. The yogurt is safe to eat and this liquid can be strained off which can decrease the sour taste of yogurt.

Is frozen yogurt as healthy as regular yogurt?

Frozen yogurt can contain more added sugar than regular yogurt as our ability to detect the sweetness decreases as the temperature drops.

Many frozen yogurt products compensate and use artificial sweeteners or plant sweeteners such as Stevia. This adds back the sweet taste with less calories than cane sugar.

For more on probiotic yogurt, check out the video below.

Does Freezing Yogurt Kill Probiotics? | Summary

Freezing yogurt does not kill probiotics and they will survive for 4-6 weeks or even more at these temperatures. Yogurt can be defrosted in the fridge and eaten or eaten frozen. When the probiotic bacteria are raised to body temperature they will reactive.

References

1. R.H. Davidson, S.E. Duncan, C.R. Hackney, W.N. Eigel, J.W. Boling, Probiotic Culture Survival and Implications in Fermented Frozen Yogurt Characteristics, Journal of Dairy Science, Volume 83, Issue 4, 2000, Pages 666-673, ISSN 0022-0302, https://www.sciencedirect.com/science/article/pii/S0022030200749277, accessed 18^th July 2022.

2. U.S. Food and Drug Administration (FDA),  CFR – Code of Federal Regulations Title 21, Mar 29, 2022, https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/cfrsearch.cfm?fr=131.200, accessed 18^th July 2022.

3. U.S. Department of Agriculture, How long can you keep dairy products like yogurt, milk, and cheese in the refrigerator?, Jul 17, 2019, https://ask.usda.gov/s/article/How-long-can-you-keep-dairy-products-like-yogurt-milk-and-cheese-in-the-refrigerator, accessed 18^th July 2022.

4. Harvard Health Publishing, Harvard Medical School, Health benefits of taking probiotics, April 13, 2020, https://www.health.harvard.edu/vitamins-and-supplements/health-benefits-of-taking-probiotics, accessed 18^th July 2022.