Next time you're at the cheese counter, take a closer look at wedges of aged gouda, aged cheddar, Parmigiano-Reggiano, and gruyere. It's likely that you'll see tiny white spots in all of them. Many types of aged cheese have these little, white crunchy bits in the paste of the cheese or on the top of it.
Commonly called "cheese crystals," there's a good reason why they form on cheese. While it may be alarming at first, nothing is wrong with your cheese. It is safe to eat and it is not mold. Just the opposite is true and most cheese lovers view it as a positive sign that they are about to eat a really delicious, aged cheese.
White Cheese Crystals
The white bits are casually referred to as "cheese crystals" or "flavor crystals." Scientists and cheesemakers call them calcium lactate crystals and tyrosine crystals, referring to two different types of crystals. Both are a natural part of the aging process, although the cheese doesn't necessarily have to be aged for a long time.
- During the aging process, good bacteria break the lactose in cheese down into lactic acid. Lactic acid and calcium combine to create calcium lactate, which can form into calcium lactate crystals.
- Tyrosine crystals from when proteins in the cheese are broken down during the aging process. An amino acid called tyrosine is released and clusters together.
There are several things that can affect the formation of crystals. In "Revisiting Calcium Lactate Crystals in Cheese," Mark Johnson, Ph.D. points out that factors such as the lactic acid content of the cheese, the cheese's moisture level, the choice of starter culture, and the storage temperature can all promote crystal growth.
Calcium Lactate vs. Tyrosine Crystals
Johnson goes further to explain both calcium lactate crystals and tyrosine crystals in "Crystallization in Cheese." Published in a 2014 edition of Dairy Pipeline by the Wisconsin Center for Dairy Research, it is a fascinating read for anyone who really wants to dive into the science of cheese crystals.
The article explains that tyrosine crystals are usually found on cheeses like Parmesan, Romano, and Swiss cheeses and sometimes in gouda and cheddar. The crystals are firmer and have a brighter white color. Tyrosine crystals are usually only found in the interior of the cheese.
Calcium lactate crystals, on the other hand, can be found in the interior of the cheese as well as on the outer surface. They are softer, less crunchy and most commonly found on aged cheddar, although may also be on Parmesan and gouda. Sometimes, the crystals can look like a thin layer of white mold on the outside of the cheese.
A cheese may have only one type of crystal while others may contain the two crystals simultaneously. Both calcium lactate crystals and tyrosine crystals add a slight and pleasant crunchiness, which is seen as a desirable trait in aged cheeses.
Crystals or Mold?
Next time you have one of these types of cheese with white bits, test it before assuming that it's mold. Most often, molds will grow on the outside of cheese first, so if you notice white specks on the inside as well, it's more likely to be crystals. You can also test the white particles for hardness—mold will be soft and crystals will be hard and crunchy. These observations can save you from throwing out an amazing cheese that really should be enjoyed!
Wisconsin Center for Dairy Research. Revisiting calcium lactate crystals in cheese. April 2004.
Wisconsin Center for Dairy Research. Crystallization in cheese. 2014.