Skyr is one of the most misunderstood dairy products available. In supermarkets outside Iceland, it’s marketed and shelved as yoghurt, and it behaves enough like thick yoghurt that most people treat it as such. But technically, skyr is a fresh soft cheese – it’s produced by adding rennet to warm cultured milk, which causes it to set differently from yoghurt and produces a product with a higher protein content, a denser texture, and a milder, less acidic flavour than Greek yoghurt. It’s been part of Icelandic food culture for over a thousand years, and the domestic version is significantly different in quality from the commercial product exported globally.
How Skyr Differs from Yoghurt
Yoghurt is produced by bacterial fermentation alone – specific bacteria consume the lactose in milk and produce lactic acid, which causes the proteins to coagulate. Skyr uses bacterial fermentation plus a small amount of rennet, the enzyme that causes milk proteins to clump together in cheesemaking. This combination produces a firmer, smoother curd that, after straining, achieves a protein content of around 10-11g per 100g – roughly double that of standard yoghurt. The whey that drains off during straining is reincorporated in commercial production (to reduce waste and add volume), but traditional skyr discards it entirely, which is why artisan skyr is thicker and richer than commercial varieties.
Making Skyr at Home
You’ll need 2 litres of skim milk (low-fat works too; use fresh pasteurised, not UHT or long-life), 1½ tablespoons (30 ml) of plain shop-bought skyr or plain yoghurt with live cultures as your starter, and 4 drops of liquid rennet from a cheesemaking supplier. You’ll also want a thermometer, a large heavy-based saucepan, and cheesecloth or muslin for draining.
Heat the milk slowly, stirring now and then, until it reaches 88 to 90°C, then take it off the heat and let it cool to between 37 and 43°C. Loosen the starter with a few spoonfuls of the warm milk, then stir it through the pot. Dilute the rennet in a tablespoon of cool water and stir it in gently. Cover the pot, wrap it in two or three towels and leave it undisturbed at room temperature for 12 to 16 hours. It’s ready when it has set into a solid mass with a little yellowish whey showing. Ladle the curd into a sieve lined with cheesecloth or muslin and set over a bowl, cover, and let it drain in the fridge. A few hours gives a soft, spoonable skyr. Leave it longer, up to two or three days, for a very thick, almost cheese-like result. Finish by whisking it until it’s smooth.
How Icelanders Eat It
Traditionally, skyr is eaten with a spoonful of cream stirred through and fresh blueberries on top – the cream adds fat that the skim milk base lacks, and the blueberries are the most traditional accompaniment in Iceland. It’s also eaten with brown sugar stirred through, with jam, with granola, or straight from the container with a spoon. The Icelandic version has a specific mild, clean flavour without the sharpness of Greek yoghurt, and the texture is dense enough to be scooped rather than poured.
Skyr is worth making at home if you have an interest in fermentation – it’s a straightforward introduction to basic cheesemaking techniques and produces something noticeably different from anything available commercially. Once you’ve made it, it’s difficult to go back to the commercial version as a substitute.
Choosing Milk and Rennet
Traditional skyr is made from skim or low-fat milk, and it is worth sticking to that. It is not about cutting calories, it is about the protein. Skim milk gives skyr its dense, firm curd and clean flavour, where full cream milk makes a softer, richer set closer to labneh. Use fresh pasteurised milk. Cheesemaking suppliers warn against UHT (long-life) milk here, because milk heated that hard won’t set properly with rennet. Ultra-filtered and lactose-free milk can set unpredictably too, so leave them for later.
The rennet is the part most people are unsure about. You only need a few drops (4 for 2 litres of milk), diluted in a little cool water, so a small bottle goes a long way. Strengths vary between brands, so check the label. Vegetarian (microbial) rennet works just as well here as animal rennet, so look for that if it matters to you. If you genuinely cannot get rennet, you can still make a skyr-style strained yoghurt without it. It sets through the culture alone, and plenty of commercial skyr is now made that way too.
Troubleshooting
The curd stayed soft or soupy. Check the milk, the rennet and the warmth. UHT milk won’t set firmly with rennet, rennet loses strength as it ages, and milk that was cooler than about 37°C when the starter and rennet went in will be slow to set. Wrap the pot well so it holds its warmth. A soft curd will still drain into something usable, it just takes longer.
It came out too sour. Sourness builds with time. Next time, start draining it at the 12 hour end of the setting time rather than 16, and keep it in the fridge while it drains.
It’s grainy. Give it a really thorough whisk once it has drained. That’s what turns the curd smooth. At the start, stir the rennet in gently rather than beating it.
It’s drier than I wanted. You have strained it too long. Stir a little of the reserved whey or a splash of milk back through to loosen it to the texture you like.
Common Questions
Is skyr a yoghurt or a cheese? Technically a fresh cheese, because of the rennet, but it is eaten and sold like a thick yoghurt. Both descriptions are fair.
How is it different from Greek yoghurt? Skyr is strained further and made with rennet, so it is denser, higher in protein, and milder. Greek yoghurt is strained yoghurt with no rennet and a sharper tang.
How long does it keep? In a sealed container in the fridge, homemade skyr keeps for about a week. Like yoghurt, the flavour sharpens over time.
What do I do with the whey? Do not tip it down the sink. It is full of protein and works in bread dough, smoothies, or soaking grains, and it keeps for a week in the fridge.
Sources
The method on this page is adapted from Magnus Nilsson’s skyr recipe, published by Saveur, and the skyr recipe from New England Cheesemaking Supply Company, whose quantities we follow, scaled to 2 litres.
