What is the name of acid present in stale cheese?

Here's why:

* Cheese making process: Cheese is made by adding lactic acid bacteria to milk. These bacteria ferment the lactose (milk sugar) into lactic acid.

* Staling: As cheese ages, the lactic acid continues to build up. This contributes to the development of sharper, more intense flavors.

* Other factors: While lactic acid is the primary acid, other acids like acetic acid (vinegar) and propionic acid can also be present in varying amounts depending on the type of cheese and aging process.

So, while "stale cheese" is a somewhat subjective term, it's the increasing lactic acid concentration that primarily contributes to the changes in flavor and texture associated with aging cheese.