The Federal Food Safety department advises that yogurt held in temperatures above 40 degrees Fahrenheit should be discarded after 2 hours. Other dairy products such as milk, cream, sour cream, buttermilk, evaporated milk, soy milk and eggnog are also to be thrown out when subjected to the same conditions.
The Federal Food Safety department is owned and operated by the United States Federal Government. It serves as an information gateway for several federal agencies that play a role in food safety. These agencies include the Food Safety and Inspection Service (FSIS), the U.S. Food and Drug Administration (FDA), U.S. Department of Agriculture and the Centers for Disease Control (CDC).
Yogurt is a type of milk product created through a fermentation process. To make yogurt in the traditional way, the milk is exposed to bacteria known as yogurt cultures. The bacteria produce lactic acid, which gives yogurt its characteristic curds and sourness. In the West, the milk is heated to kill off any pathogens and to denature the protein in the milk for the yogurt to set rather than curd.
Jeff Potter, a food science expert and author of Cooking for Geeks, claims that yogurt may still be eaten after 8 hours outside the fridge. According to Potter, since yogurt is a probiotic, the beneficial bacteria that it contains will only increase in number without refrigeration. He adds, however, that yogurt at room temperature may not be as palatable for some people.