Frozen yogurt and live cultures
Do yogurt cultures survive freezing? What the measurements say, how much sugar frozen yogurt contains and how to make it at home without killing the cultures with heat.
Frozen yogurt has a reputation as a lighter, “livelier” alternative to ice cream. It’s often associated with the live cultures found in ordinary yogurt. But do they survive freezing? And is frozen yogurt really lighter? The answers are more interesting than you might think.
Do the cultures survive freezing?
Yes, but not all of them. Freezing usually doesn’t kill bacteria straight away, but ice and cold damage some of the cells. This is shown well by a study published in 2026 in the journal Fermentation (MDPI), which tracked culture counts in frozen yogurt:
| Stage | Streptococcus thermophilus | Bifidobacterium animalis subsp. lactis |
|---|---|---|
| Freezing itself | drop of 0.43–0.63 log | drop of 0.67–0.79 log |
| A further 90 days at −20 °C | drop of 0.78–1.11 log | drop of 1.21–1.41 log |
The biggest losses came in the first month of storage. This is a single study with a specific recipe, so treat the figures as indicative.
What “log” means
Microbiologists count bacteria in logarithms. A drop of 1 log means one tenth of the bacteria remain. A drop of 0.5 log means roughly a third remain. In practice, then, after freezing and three months in the freezer only a few per cent of the original cultures may be left in the yogurt — depending on the type of bacterium.
Did you know?
Live cultures partly survive freezing, but their numbers fall both during freezing and during storage. Fresh frozen yogurt has the most (MDPI Fermentation study, 2026).
An older paper in the Journal of Dairy Science (2000) also looked at the survival of probiotic cultures in frozen yogurt. We didn’t have access to the full text, so we don’t quote figures from it.
Frozen yogurt and health claims
Words like “probiotic” or “supports digestion” sometimes appear on packaging. In the EU, foods may carry only approved health claims. zmrzka therefore doesn’t claim that frozen yogurt has any curative or protective effects. It’s a tasty dessert that contains live cultures — nothing more and nothing less.
Is frozen yogurt lighter?
In terms of calories, yes. In terms of sugar, no. Figures from the USDA FoodData Central database per 100 g:
| Product | kcal | Fat | Sugars |
|---|---|---|---|
| Vanilla ice cream | 207 | 11.0 g | 21.2 g |
| Frozen yogurt | 127 | 3.6 g | 19.9 g |
| Vanilla frozen yogurt, soft-serve | 159 | 5.6 g | 24.0 g |
Frozen yogurt has less fat and therefore fewer calories. But it contains practically as much sugar as ice cream. The World Health Organization (WHO, 2015) recommends limiting free sugars to below 10 % of daily energy intake — and added sugar in frozen yogurt counts towards this just as it does in ice cream. Lactose from milk and yogurt is not a free sugar.
Tip
The acidity of yogurt suppresses the perception of sweetness, so frozen yogurt needs quite a lot of sugar to taste right. If you want it less sweet, add ripe fruit in place of some of the sugar.
How to make frozen yogurt so the cultures survive
The biggest enemy of the cultures when making it at home isn’t the cold but heat. If you heated the yogurt together with the mix, you would kill the cultures before freezing even began. So the method goes like this:
- Heat the milk, sugar and any stabiliser so that everything dissolves and the mix is pasteurised.
- Chill the mix completely in the fridge.
- Only then stir plain yogurt into the cold mix — in recipes it is often 40–50 % of the mix.
- Churn the mix in an ice cream maker or freeze it another way.
- Eat it as soon as possible, ideally within a few days.
Warning
Don’t pasteurise the yogurt with the mix or boil it with the milk. Heating kills the cultures, and the result is just sour ice cream with no live bacteria.
What matters
- Good-quality yogurt. Choose yogurt that lists live cultures and has no unnecessary additives.
- Greek-style yogurt has more solids and protein, so the frozen yogurt will be thicker and less icy.
- Short storage. The longer the yogurt sits in the freezer, the fewer cultures remain and the more the ice crystals grow.
Soft-serve frozen yogurt in cafés
In cafés and kiosks, frozen yogurt is often sold soft-serve from a machine. Whether it contains live cultures depends on how it’s made — some places use powdered mixes. If you’re curious, ask on the spot.
Summary
- Cultures partly survive freezing; their numbers fall during both freezing and storage.
- Frozen yogurt has fewer calories and less fat, but about as much sugar as ice cream.
- Add the yogurt to the chilled mix and eat frozen yogurt fresh.
- Take health claims such as “probiotic” with a pinch of salt.
Sources
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