While there’s a basic recipe, different manufacturers, even different countries, each make it in their own way. For example, Greek and Icelandic yogurts strain their yogurts more to give them a thicker consistency. Here’s the general process:
It all starts with fresh milk. You can make yogurt at home with whole milk, but some manufacturers will first separate it into cream and skim milk. They then thicken the milk by either evaporating it or adding gelatin or milk powder.
Once the milk is thick, they pasteurize it to ensure its safety and homogenize it to make sure it says creamy.
At this point, good bacteria are added to the milk. These bacteria, Lactobacillus bulgaricus and Streptococcus thermophiles, are starters or “cultures” for yogurt. The milk is then kept warm at a specific temperature so the bacteria can work, that is, the bacteria change milk’s natural sugar (lactose) into lactic acid. This thickens the milk more and gives it yogurt’s familiar tangy flavor.
Once the milk becomes yogurt, that’s when manufactures – or even you at home – can add in sweeteners, fruit or other add-ins.
Want to try making this at home? The Kitchn has a step-by-step slideshow and video to help!