Why does Swiss cheese develop pink or orange streaks?

The pink or orange streaks in Swiss cheese are caused by a harmless bacteria called Propionibacterium freudenreichii.

Here's how it works:

* Propionibacterium freudenreichii is a naturally occurring bacteria present in milk. It's introduced into the cheese during the cheesemaking process.

* During the aging process, this bacteria breaks down lactic acid produced by other bacteria, releasing propionic acid, acetic acid, and carbon dioxide.

* Propionic acid is the key factor. It gives Swiss cheese its characteristic flavor and aroma. But it also interacts with other molecules in the cheese, particularly riboflavin, a vitamin B found naturally in milk.

* This interaction creates a compound called "riboflavin degradation product", which is responsible for the pink or orange streaks. The color intensity depends on the amount of riboflavin present and the length of the aging process.

It's important to note that:

* This discoloration is entirely natural and harmless. The pink or orange streaks are not a sign of spoilage or contamination.

* The streaks are actually a sign of good quality Swiss cheese. They indicate that the cheese has been aged properly and that the bacteria have had time to develop the characteristic flavor.

So next time you see pink or orange streaks in your Swiss cheese, don't worry – enjoy the delicious taste!