Yogurt has always been a popular snack here in the United States, but the past decade or so has seen a rapid expansion in the varieties (or styles) of yogurt being sold. We now have Icelandic and Greek style yogurts available alongside traditional yogurt, in addition to yogurt drinks like kefir, which offer people the many benefits of yogurt without the need of a spoon.
While variations on yogurt exist (and we will discuss those differences later), all yogurt varieties are made in roughly the same way. The only initial difference is in the type of bacteria used in the fermentation process. There are two varieties, thermophilic (warm loving) bacteria and mesophilic (cool loving). The thermophilic bacteria cultures at 110 degrees F, while the mesophilic variety cultures at about 70-77 degrees F. Both work in the same way: The bacteria consume the lactose in milk and converts that lactose to lactic acid, which is what gives yogurt its tangy flavor. The lactic acid also lowers the pH of the milk -- allowing it to be stored for longer periods -- and changes the protein structure, resulting in its yogurt's thickened texture.
Greek Yogurt VS. Regular Yogurt
The only significant difference between standard yogurt and Greek lies in the straining process. To make Greek yogurt, regular yogurt is strained extensively to remove more of the liquid whey and lactose to create a thicker texture. Aside from the mouth-feel, Greek yogurt boasts substantial nutritional differences from regular yogurt as well: It contains twice the protein and half the sodium and carbohydrates, which is great, but it also has three times the saturated fat...not so good.
Also known as skyr, this style of yogurt is essentially a step up from Greek as far as processing. The straining process is a bit more thorough, with even more whey being extracted. The result is a much more less tart and more dense yogurt – one that will practically stick to your spoon like batter. Tradtionally, skyr is made with nonfat yogurt, while Greek yogurt is typically derived from full-fat varieties (although in the American market, non- or low-fat varieties are also popular).
So, what about kefir?
Kefir has a tart and refreshing flavor similar to yogurt and the culturing process is similar, but it contains beneficialyeast as well as the probiotics (friendly bacteria) found in yogurt. Kefir can be made from any type of milk, but cow and goat's milk varieties are the most common.
Kefir is made from gelatinous white or yellow particles called "grains." This makes kefir unique, as no other milk culture forms grains. These grains contain the bacteria/yeast mixture clumped together with casein (milk proteins) and complex sugars. They look like pieces of coral or small clumps of cauliflower and range from the size of a grain of wheat to that of a hazelnut. The grains ferment the milk, incorporating their friendly organisms to create the cultured product. The grains are then removed with a strainer before consumption of the kefir. -- kefir.net
Health benefits of yogurt and yogurt products
Yogurt can aid in digestion - Yogurt is made by bacterial fermentation of milk, a process that may boost digestive health because it produces the same good bacteria found in the gut. These useful bacteria are referred to as probiotics and, in additional to assisting with regular digestion, are known to help reduce the symptoms of irritable bowel and relieve abdominal pain and gas.
Yogurt can help boost your immunity - According to some studies, the probiotics in yogurt can help enhance immunity, possibly by producing more infection-fighting white blood cells.
Yogurt can help with blood pressure - Yogurt is rich in potassium, which is known to help lower blood pressure. It is also critical for enabling the heart to beat properly.
Yogurt contains lots of vitamins and minerals – One serving of yogurt contains fair to high amounts of potassium, phosphorus, vitamin B5, zinc and riboflavin. It is also rich in B12, which is necessary for maintaining red blood cells, and aids in nervous system function.