- Heating milk to 180°F denatures whey proteins for a thicker curd, but heating your starter above 110°F kills the live active cultures.
- I don’t recommend using more than 2 tablespoons of starter per gallon of milk; too much starter crowds the bacteria and makes the final dairy thin and sour.
- Traditional skyr is technically a fresh acid-set cheese made with rennet, not a standard yogurt, which gives it a dense, dry texture.
- The ropy, stringy texture in kefir grains is kefiran, a beneficial polysaccharide – do not throw your grains out if they develop it.
- Viili cultures at room temperature, making it one of the easiest Scandinavian fermented dairy traditions to maintain daily without any heating equipment.
I eat 500g to 750g of yogurt daily to fuel a 3500-calorie diet for heavy weightlifting and hockey. When I was buying store-bought Skyr at $4 per container, the cost added up fast, so I switched to making a 2500g batch at home for around $4.00 to $5.00 CAD.
Making your own cultured dairy completely changes how you view the kefir vs viili vs skyr debate. You stop relying on grocery store shelves and start relying on live active cultures that actually support your gut microbiome.
As a dietitian focused on regenerative farming, I always tell people that the quality of your starter matters less than the quality of your milk. Milk from cows raised on diverse, biodiverse pastures provides a richer foundation for these traditional fermented dairy traditions.
I was talking about this recently with a local gardener I advised about preserving herbs and vegetables. She wanted to know if the same principles of biodiversity she used in her soil applied to dairy fermentation.
The answer is yes. The healthier the soil and the forage, the more diverse the microbial environment in the raw milk, which gives your cultures a better starting point.
But once you have good milk, the technique you use determines the final product. Each of these three ferments requires a completely different approach to temperature, time, and texture.
What is the Real Difference Between Kefir vs Viili vs Skyr?
These three foods look similar in a jar, but they rely on entirely different fermentation processes and microbial profiles. Understanding these differences is the first step to mastering traditional fermented dairy.
Dairy kefir is fermented using kefir grains, which are symbiotic colonies of bacteria and yeast. These grains look like tiny cauliflower florets and cannot be replicated by simply mixing commercial bacteria.
Viili is a (mesophilic – meaning it ferments at moderate room temperatures rather than requiring heat) Scandinavian-origin fermented milk that cultures at ambient room temperature. It relies on *Streptococcus* and *Lactococcus* strains rather than the thermophilic bacteria found in other yogurts.
Traditional Eastern European yogurt, by contrast, is cultured with *Lactobacillus bulgaricus*. This strain requires heat to ferment properly, which is why you need a yogurt maker or a warm oven.
Skyr is technically classified as a fresh, acid-set cheese made from skimmed milk and rennet rather than a standard yogurt. This distinction matters because the rennet changes the texture entirely.
Old-school skyr has a dry, crumbly consistency that requires thinning with milk, a preparation referred to as *hrært* or stirred. If you eat traditional skyr in Iceland, it rarely resembles the smooth cups sold in American grocery stores.
Commercial skyr sold in the United States generally does not follow the traditional rennet-cheese recipe or utilize an established skyr bacterial blend. Instead, it relies on standard yogurt cultures to bypass yogurt standard-of-identity regulations.
This regulatory workaround allows companies to market a yogurt product as skyr without adhering to the traditional Icelandic methods. This is why homemade skyr often tastes and feels completely different from the cups you buy at the store.
The typical nutritional profile for skyr runs roughly 13 g protein, 4 g carbohydrates, and 0.2 g fat per 100 g. This yields about 20 g of protein per 122 calories in a 200 g portion, making it incredibly dense nutritionally.
The low fat content is a result of the traditional skimming process, where the cream was skimmed off to make butter. What remains is a protein-dense curd that sustained Viking farmers through harsh winters.
These Nordic and Scandinavian fermentation traditions evolved out of necessity. In cold climates, preserving milk through fermentation was essential for survival when fresh forage was unavailable.
Each region developed its own unique cultures based on the native bacteria present in their environment. This is why viili, filmjölk, and skyr all have distinct textures and flavors despite originating in similar climates.
How Do You Make Traditional Skyr at Home?
When I first tried making yogurt with Siggi’s plain skyr as a live starter and pasteurized whole milk, it came out thin like drinking yogurt. The reason my first batch failed to thicken was that I had the temperature wrong and killed the bacteria by heating it too high.
I also realized I had used 2 to 3 tablespoons of starter for only 4 cups of milk, which was far too much starter for that volume. Using too much starter crowds the bacteria, leaving them without enough food, which results in a thin, overly sour product.
To make traditional-style skyr at home, heat a gallon of whole milk slowly over low heat on the stove to 180°F to prevent scalding. You must stir it constantly to keep the milk from burning on the bottom of the pot.
Heating milk to 180°F to 185°F before cooling and inoculation denatures and uncoils whey proteins to improve final curd thickness. It also sanitizes the milk against native bacteria and evaporates excess water to minimize whey separation.
Take it off the heat and allow it to cool to 110°F. This cooling step is critical because anything hotter than 110°F will kill your starter culture instantly.
Whisk in two spoons of store-bought skyr yogurt along with rennet. The rennet is what separates true skyr from standard yogurt, as it creates a firmer curd.
Transfer the mixture to a crock pot set on warm at 110°F for 4 hours, switching it off if it exceeds 110°F and back on when it drops near 100°F. Maintaining this temperature range is the most difficult part of the process.
Once the curd pulls away from the sides of the crock pot, ladle the curds into a yogurt strainer overnight. Straining cultured yogurt or skyr removes liquid whey, which contains about 5% lactose and less than 1% protein.
I shared this exact method with a family I’ve advised about traditional food preparation, Amanda. She wanted a high-protein breakfast option without the steep grocery store markup.
She now heats a gallon of milk to 180°F in a stainless steel pot, places the pot in a cold water sink until the temperature drops to around 110°F, and stirs in 1 cup of plain store yogurt until smooth.
She covers the pot, wraps it in a towel, places it in an insulated cooler overnight, and then transfers the cultured yogurt into a cheesecloth-lined colander dangling over a pot in the fridge overnight to let the whey drip out into a thick Skyr.
The result is a remarkably thick, protein-dense dairy product that costs a fraction of the commercial equivalent. Amanda told me her kids actually prefer the homemade version because it feels richer than the store-bought cups.
You do have to watch the temperature closely, as a few degrees too high will kill your culture. I recommend using a digital thermometer with an alarm to alert you when the milk hits the target temperatures.
The whey that drains out is also valuable. You can use it to ferment vegetables, soak grains, or add it to smoothies for a boost of bioavailable minerals.
How Do You Culture Viili at Room Temperature?
I make viili almost every day, a practice I learned from an older relative who taught me this method. My Finnish grandmother called it filli-bunke.
Viili is characterized by a mild, less tart taste than standard yogurt and an elastic, gelatinous, or ropey consistency. This unique texture comes from the specific exopolysaccharide-producing bacteria in the culture.
I use whole milk at a ratio of 1 tablespoon of viili yogurt to each 1 cup of milk. This ratio ensures the culture has enough food to ferment the milk without becoming overly sour.
In the morning, I scoop 5 tablespoons of viili into a wide-mouth mason jar, pour in 5 cups of whole milk, and stir it with a fork. I cover the jar with a coffee filter secured by a rubber band and let it sit on a kitchen shelf for 4 to 10 hours at room temperature.
I check it by giving the jar a wiggle. Once it is lightly set, I cap it and place it in the refrigerator.
We never strain it. It can be ropey, though giving it a stir while processing reduces the ropiness.
Whenever I get a culture going, I scoop a couple of tablespoons into the freezer, where the starter remains viable for 6 months. This backup method is crucial because a single contaminated batch can ruin your ongoing culture.
There is also a Finnish variant called *Kermaviili*. It is prepared with cream rather than whole or skim milk and is commonly used in Nordic cooking as a cold sauce base.
It resembles buttermilk in flavor with a thick yogurt texture. I often use it as a base for salad dressings or as a topping for fresh berries.
I often recommend viili to people who are intimidated by thermometers and complex heating steps. As long as your kitchen is between 68°F and 75°F, the mesophilic cultures will do the work for you.
The only downside is the texture, which some people find off-putting if they are used to smooth, commercial yogurt. A quick stir before eating usually solves the problem.
The mild flavor makes it incredibly versatile in the kitchen. You can use it in place of sour cream, yogurt, or buttermilk in almost any recipe.
Because it ferments at room temperature, it also introduces less environmental stress than thermophilic ferments. This means the culture tends to be more resilient and forgiving over time.
If you travel or forget about a jar, viili will usually just separate into curds and whey rather than spoiling. You can often rescue it by stirring it back together.
Is Dairy Kefir Actually Better Than Homemade Yogurt?
I made yogurt at home for about 20 years before discovering DIY kefir. Kefir is significantly easier and cheaper because it cultures at room temperature without requiring any heating process.
While kefir enthusiasts point out that standard yogurt has few strains while kefir can have 54, in practical experience I doubt it creates a noticeably different health effect than homemade yogurt. The gut microbiome benefits from a diverse intake of live active cultures, but more strains do not automatically mean better digestion.
Kefir fermentation involves yeast activity that naturally generates roughly 1/2% or less alcohol alongside its sour profile, whereas Scandinavian filmjölk does not produce alcohol. This is why kefir has a slight effervescence and a sharper, more complex flavor.
Years ago I ordered kefir grains from the “KefirLady” that produced rich, creamy kefir. Over time, the grains became coated with a ropy, stringy substance that clung to them.
Even though the kefir tasted fine, the stringiness alarmed me, so I discarded them and started over with a new batch of grains. That turned out to be a mistake, because the replacement grains completely lacked that stringy quality, which is produced by an abundance of (kefiran – a complex polysaccharide produced by Lactobacillus kefiranofaciens that gives kefir its thick, smooth texture).
Kefir contains a highly complex mix of probiotic strains. Lactobacillus paracasei ssp.
paracasei, Lactobacillus acidophilus, Lactobacillus delbrueckii ssp. bulgaricus, Lactobacillus plantarum, and L.
kefiranofaciens are predominant species.
However, these species represent only 20% of the Lactobacillus in the final fermented beverage, with the remainder consisting of Lactobacillus kefiri at 80%. Acetobacter aceti and A.
rasens have also been isolated.
More than 23 different yeast species have been isolated from kefir grains and from fermented beverages of different origins. The predominant species are Saccharomyces cerevisiae, S.
unisporus, Candida kefyr, and Kluyveromyces marxianus ssp. marxianus.
Jason, someone from our farmers market, asked me about boosting the thickness of his homemade kefir. When adding milk powder to boost protein and thickness, I found that adding 1/2 cup of powdered milk required shortening the incubation time by an hour or two.
Otherwise, the batch became excessively sour because the nonfat dry milk is roughly 50% lactose, providing extra fuel for the lactic acid bacteria. The bacteria consume the extra lactose and produce more lactic acid, which quickly turns the kefir sour.
I also recently saved some Greek yogurt that was about to spoil by stirring kefir directly into it, doubling the volume. This resulted in the creamiest yogurt consistency I have ever achieved.
The kefir grains continued to ferment the Greek yogurt, breaking down the proteins further and creating a texture that was incredibly smooth. This is a great trick if you have yogurt that is approaching its expiration date.
Megan, someone I helped get started with water kefir, found that maintaining dairy ferments was actually easier once she understood the temperature differences. If you are exploring non-dairy ferments, you might look into a water kefir vs kombucha vs tepache setup, which uses different sugars and substrates but follows similar principles of managing live cultures.
The main advantage of kefir over yogurt is the convenience. You simply put the grains in milk, let it sit on your counter, and strain it out 24 hours later.
The main disadvantage is the taste. Kefir is noticeably more sour and yeasty than yogurt, which some people find unpleasant.
You can mitigate this by doing a shorter ferment or by adding fruit after the fermentation is complete. I do not recommend adding fruit before fermenting, as the sugars can disrupt the bacterial balance.
Kefir vs Viili vs Skyr: Which Should You Start With?
If you want a high-protein, thick dairy product, skyr is the best choice, provided you are willing to manage temperatures and straining. The process is more involved, but the nutritional payoff is significant.
If you want a daily, low-maintenance fermented milk, viili is unmatched because it requires no heating and sets on your counter. It is the most forgiving culture for beginners.
If you want a complex probiotic beverage that you can drink, kefir is the way to go. The yeast and bacteria combination creates a unique flavor profile that pairs well with fruit.
When clients ask me to settle the kefir vs viili vs skyr debate, I tell them to start with viili. The margin for error is nearly zero, and the texture is a gentle introduction to traditional fermented dairy traditions.
Once you master viili, you can move on to skyr or kefir with a better understanding of how live active cultures behave. The key is to start with high-quality milk and to trust your senses.
Fermentation is as much an art as it is a science. Your kitchen environment will influence the final product, so do not be afraid to adjust timings and ratios to suit your taste.
