How does moisture migration happen?

For example, moisture migration in retail packages of shredded cheese is a common problem.

Inside the package, moisture is lost to air. Moisture comes from warm cheese in the front of packaging, meanwhile the cheese and the back of the packaging remains cold.

When the humid air inside of the package meets the cold cheese, it condenses. The cold cheese then absorbs the water, the cheese become soft and pasty.

Moisture migration also occurs in packaged brine cheese, like Mozzarella. High salt attracts moisture from lower salt areas in the interior of the cheese. Resulting the outer portion of the cheese may become pasty and mushy.