Is purple discoloration on mozzarella cheese harmful?

The purple discoloration on mozzarella cheese is caused by a bacteria called Serratia marcescens. This bacteria is commonly found in soil, water, and other environments, and it is not considered to be harmful to humans. The purple pigment produced by the bacteria is a result of the way it absorbs and reflects light.

While the purple discoloration may not be appetizing, it is not an indication that the cheese is spoiled or unsafe to eat. However, if you are concerned about the appearance of the cheese, you can always return it to the store for a refund or exchange.