Figaro Shakes
Cultural Ferment

Skyr: How Icelandic Skyr Is Made, Is It Fermented, and a Homemade Skyr Recipe

By Updated 2 min read

Learn to make authentic Icelandic skyr at home—thicker than Greek yogurt, with 11g protein per serving and Viking Age heritage. Includes step-by-step fermentation, straining guide, and troubleshooting.

At a glance

Skyr is Iceland's thick, high-protein cultured dairy food, and yes, it's fermented: skimmed milk is fermented with skyr cultures, then strained of its whey. It takes 3–4 times the milk of yogurt; plain skyr has about 11 g protein and 0.2 g fat per 100 g. At home: heat skim milk, cool to 40–43°C, culture with plain skyr, then strain.

  • Skyr is fermented: skimmed milk cultured with lactic acid bacteria, then strained.
  • Made with 3–4 times more milk than ordinary yogurt (Ísey Skyr).
  • Plain skyr: 61 kcal, 11 g protein, 0.2 g fat, 3.7 g carbohydrate per 100 g.
  • Traditionally made from the skimmed milk left after making butter.
  • Contains live cultures unless heat-treated after fermentation – check the label.

Ferment profile

Origin
Iceland
Fermentation
Lactic acid
Main microbes
Skyr cultures (thermophilic lactic acid bacteria)
Live cultures
Yes
Alcohol
None / trace

Skyr is Iceland’s traditional cultured dairy food: very thick, mild and high in protein. Yes, skyr is a fermented food. It’s made by fermenting skimmed milk with skyr cultures (lactic acid bacteria), then straining off the whey so the curd is concentrated. It takes 3–4 times as much milk as ordinary yogurt, which is why it’s so thick and high in protein (Ísey Skyr). Although it’s eaten like yogurt, it’s traditionally classed as a fresh cheese.

How Skyr Is Made

  1. Skimmed milk: on Icelandic farms, milk was separated into cream for butter and skimmed milk for skyr, which is why skyr is naturally almost fat-free (Ísey Skyr FAQ).
  2. Heating: the milk is heated, then cooled to a warm fermenting temperature.
  3. Culturing: skyr cultures – traditionally a spoonful from the last batch – are added, and the milk ferments until it sets into a soft curd. Some recipes also add a little rennet.
  4. Straining: the curd is drained of its whey (mysa) until thick, then whisked smooth.

Skyr Nutrition

Plain Icelandic skyr (Ísey Skyr Natural, made from skimmed milk and skyr cultures) has per 100 g: 61 kcal, 11 g protein, 0.2 g fat and 3.7 g carbohydrate (Ísey Skyr). According to the maker, its bacterial cultures are alive and active (Ísey Skyr FAQ); for other brands, check the label for live cultures. Like other fermented foods, it’s the product of microbial growth, but that doesn’t by itself make it a probiotic – a term reserved for specific, tested strains (Marco et al., 2021).

Skyr vs Greek Yogurt

  • Both are strained, which makes them thick and high in protein.
  • Skyr is made from skimmed milk and is typically fat-free, milder and thicker; Greek yogurt comes in full-fat and low-fat versions.
  • Cultures differ: skyr uses its own traditional cultures; Greek yogurt uses yogurt cultures.
  • Both work the same way in recipes – see our Greek yogurt recipes.

How Skyr Is Eaten in Iceland

Traditionally with a little cream or milk and sugar, or with berries; today also in smoothies, desserts and as a snack. The drained whey was historically kept and used too.

Related: our homemade yogurt guide, and Nordic fermented milks filmjölk and viili.

Recipe: Homemade Skyr

Makes
About 500–600 g
Hands-on
30 min
Fermentation
4–6 hours at 40–43°C, then 4–12 hours straining in the fridge
Temperature
40–43°C (104–109°F)
Difficulty
Moderate

Equipment

  • Heavy pot
  • Thermometer
  • Oven with the light on, cooler or yogurt maker
  • Sieve lined with fine cheesecloth
  • Bowl and whisk

Ingredients

  • 2 litres skimmed milk (pasteurized, not UHT)
  • 2–3 tbsp plain skyr with live cultures (or plain live yogurt)
  • 2–3 drops liquid rennet (optional, diluted in 1 tbsp cool water)

Method

  1. Heat the milk to 82–85°C (180–185°F), stirring, and hold for 5 minutes.
  2. Cool to 40–43°C (104–109°F).
  3. Whisk the skyr into a cup of the warm milk, then stir it into the pot (add the diluted rennet now, if using).
  4. Keep at 40–43°C, undisturbed, for 4–6 hours until set like soft custard.
  5. Ladle into a cheesecloth-lined sieve over a bowl and strain in the fridge for 4–12 hours – longer for thicker skyr.
  6. Whisk until smooth and glossy. Refrigerate and eat within about a week; save 2–3 tbsp to start the next batch.

Frequently asked questions

Is skyr fermented?

Yes. Skyr is skimmed milk fermented with lactic acid bacteria (skyr cultures) and then strained, so it's a fermented food.

How is skyr made?

Skimmed milk is heated, cooled, fermented with skyr cultures until it sets, then strained of its whey until very thick, and whisked smooth.

Is skyr yogurt or cheese?

It's eaten like yogurt, but because the curd is strained from the whey (and sometimes set with a little rennet), it's traditionally classed as a fresh cheese.

How much protein is in skyr?

Plain Icelandic skyr has about 11 g of protein per 100 g, with almost no fat.

Does skyr have live cultures?

Usually yes – Ísey Skyr says its cultures are alive and active. Check the label of other brands.

What's the difference between skyr and Greek yogurt?

Both are strained and high in protein, but skyr is made from skimmed milk with its own traditional cultures and is usually milder and thicker.

Can I make skyr without Icelandic cultures?

You can make a skyr-style strained product with plain live yogurt as the starter; for the traditional flavor, use plain skyr as the starter.

Sources

  1. Ísey Skyr (MS Iceland Dairies). Ísey Skyr Natural – ingredients and nutrition. Link
  2. Ísey Skyr. Our skyr. Link
  3. Ísey Skyr. Frequently asked questions. Link
  4. Marco ML et al. (2021). The International Scientific Association for Probiotics and Prebiotics (ISAPP) consensus statement on fermented foods. Nat Rev Gastroenterol Hepatol 18:196–208. Link
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