For thicker yogurt, the milk is heated longer.
Next, the milk is rapidly cooled to approximately 112° Fahrenheit (44° Celsius) and mixed with a yogurt starter, which contains the necessary bacteria.
This dairy mixture is placed in clean containers and incubated for a minimum of four hours at 100° Fahrenheit (37° Celsius). The longer the incubation, the more tart the yogurt, because more acids will develop.
To stop the incubation, the yogurt is placed in a cool environment such as a fridge.
Kept cold, it will keep for approximately ten days.
Yogurt can be made at home using commercial yogurt as a starter.