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 - although the cheese doesn't necessarily have to be aged for a long time - have these little, white crunchy bits in the paste of the cheese or on the top of the cheese.
White Cheese Crystals
These white bits are casually referred to as "cheese crystals" or "flavor crystals." Scientists and cheesemakers call them calcium lactate crystals or tyrosine crystals. They are a natural part of the aging process and viewed by most cheese lovers to be a positive thing, an indication that they are about to eat a really delicious, aged cheese.
During the aging process, good bacteria breaks the lactose in cheese down into lactic acid. Lactic acid + calcium = calcium lactate, which can form into calcium lactate crystals. Tyrosine crystals from when proteins in the cheese are broken down during the aging process and an amino acid called tyrosine is released and clusters together.
There are several things that can affect the formation of crystals. The lactic acid content of the cheese, the moisture level of the cheese, the choice of starter culture, and the storage temperature of the cheese are all mentioned in an article by Mark Johnson, Ph.D, Revisiting Calcium Lactate Crystals in Cheese.
A blog post by Cheese Underground links to another great article by Mark Johnson called Crystallization in Cheese, that will tell you everything you've ever want to know about both calcium lactate crystals and tyrosine crystals.
Calcium Lactate Crystals vs. Tyrosine Crystals
The article above 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 can be found in the interior of the cheese and on the outer surface. They are softer, less crunchy and most commonly found on aged Cheddar, although also 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, or both calcium lactate crystals and tyrosine crystals might be present.
Both calcium lactate crystals and tyrosine crystals add a slight and pleasant crunchiness to cheese. It is commonly agreed that the crystals are a positive addition to aged cheeses.