Bloating Cheese

Parmesan Bloating

Q. I have a Parmesan which I made in January and it seems to be bloating/swelling some in the cheese fridge which is 85% humidity and approx 49-53°F.  Is this normal in the aging process?

A. No, this is not normal for the style of cheese.It's an indication that there are some undesirable bacteria working inside. Give it a good slap or two and listen for a hollow sound before opening it. If you don't hear it, perhaps it is just the outside shrinking more than the center due to dehydration.

We would suggest opening it now, just to see what is going on inside. The size of the holes and whether they are round or irregular, as well as where they are located will tell a story about what happened.

  • Many small, round holes, are usually from a coliform infection. This is a big problem in dry dusty weather when milk is left exposed.
  • Large, shiny, round holes could be contamination from a bacteria similar to what makes Swiss, these usually appear when the cheese is aged too warm.
  • Irregularly shaped holes can be from poor curd management when draining and pressing.
  • Large central holes which sometimes split the entire cheese are butyric bacteria which usually have a noxious smell. When you see these, its either really dirty milk or poorly fermented silage.

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