Why does cheese have white spots on it?

White spots on cheese are typically caused by a type of bacteria called Propionibacterium freudenreichii, which is also responsible for the "eyes" or holes in Swiss cheese. These spots are formed when the bacteria produce gas bubbles that become trapped in the cheese during the aging process.

This type of bacteria can occur naturally in milk or can be added during the cheesemaking process. As it grows and multiplies, it converts lactic acid into propionic acid and carbon dioxide gas, leading to the formation of the characteristic spots and holes. Some cheeses, like Emmental and Gruyère, are known for having these white spots, which are considered a desirable attribute and contribute to their unique flavor and texture.

It's important to note that not all white spots on cheese are caused by Propionibacterium freudenreichii. Sometimes, they can be a result of mold or yeast contamination, which can cause undesirable changes in the cheese's flavor and appearance. If you're concerned about the safety or quality of cheese with white spots, it's best to consult a food safety expert or cheese specialist.