Both are fermented milk, but they are made with different cultures and at different temperatures. Yogurt is fermented with a few types of bacteria at around 42–45°C / 108–113°F; the result is a firm product that can be scooped with a spoon. Kefir is fermented at room temperature with a culture containing many types of bacteria and yeast; it is thinner, pourable, and more sour. In cooking, one can replace the other only to a limited extent.
The 2 products start the same way: with milk and a culture. They differ in the culture itself and the fermentation conditions. Yogurt is fermented with several heat-loving types of bacteria at around 42–45°C / 108–113°F; if this temperature is not maintained, the result will not set. Kefir’s culture is much more complex; it contains many types of bacteria as well as yeast, and fermentation takes place at room temperature. That is why you do not need special heating equipment to ferment kefir. So even though the two products are sold on the same shelf, they are not interchangeable ingredients in the kitchen.
This difference directly affects the texture. The bacteria in yogurt quickly acidify the milk, and the proteins form a firm curd; the product can be scooped with a spoon and holds together enough to cut with a knife. Acidification in kefir proceeds more slowly and in a more complex way; the curd stays loose and the product becomes pourable. That is why kefir goes in a glass and yogurt in a bowl. Kefir’s texture also changes with fermentation time; the longer it ferments, the thicker and more sour it becomes.
There is also a noticeable difference in taste. Yogurt is sour, but its sourness is one-dimensional. Because yeast is active in kefir too, its flavor is sharper, a little more complex, and slightly fizzy; you may hear a light release of gas when you open the bottle. This fizz is not a sign of spoilage; it is a natural result of fermentation. Still, do not fill the bottle to the top. Keep it upright in the refrigerator and loosen the cap slowly each time you open it. Since pressure in the bottle increases over time, kefir that has been left for a long time may overflow when opened.
The fermentation setup also differs. Yogurt is started with a bowl of yogurt, and some is saved from each batch to start the next one. Kefir is made with a culture called kefir grains, which form gelatinous clumps; the grains are strained out, used again and again, and multiply over time. In other words, the yogurt starter is used up, while the kefir culture remains and is maintained. Rinse the grains after each batch and put them into fresh milk; they require regular care. If you are not going to use the grains, let them rest for a while in milk in the refrigerator.
In cooking, kefir can partially replace yogurt. It can easily stand in for a yogurt drink and sour milk; it works well as an acid source in baked goods and helps them rise when used with baking soda. In contrast, it is too thin for sauces that need body, such as a yogurt and cucumber dip. It is also more sensitive to heat than yogurt and curdles more quickly when added to hot food. If you want to make a sauce with kefir, strain it first to thicken it. Yogurt is much less likely to curdle if it is tempered before being added to hot food.
A Note for Readers
This content is for informational purposes only and is not a substitute for medical advice. Consult your doctor before making any decision about your health.
Comments (4)
Kıvam farkının kültürden geldiği açıklaması iyi olmuş, ben kefirin sulu olmasını kusur sanıyordum.
Kefirin oda sıcaklığında mayalandığını bilmiyordum, yoğurt gibi sarıp sarmalayıp sıcak yerde bekletiyordum. Sonuç hep ayran kıvamında ve fazla ekşi oluyordu. Battaniyeyi kaldırıp mutfak tezgâhında bıraktığımdan beri kıvam da tat da beklediğim gibi çıkıyor.
Kefir tanesiyle yapılanla market kefiri arasında da fark var mı?
Var. Tane, bakterinin yanında maya da taşıyor; ev yapımı kefir bu yüzden daha keskin ve hafif köpüklü oluyor. Market ürünlerinin bir bölümü yalnız seçilmiş bakterilerle üretiliyor ve tadı daha yumuşak kalıyor.
Ekşiliği fazla gelenler için son bir iki saati buzdolabında geçirmek işe yarıyor, mayalanma yavaşlıyor.