Crystal formation in cheese can create a number of challenges for both natural and processed cheese manufacturers. While crystals do not directly affect flavor, they have considerable effect on the visual and textural appeal of a cheese.

Crystals often deter consumers who may mistake the white crystals for mold growth on their cheese. Generally brought on by an imbalance in solubility, crystals range from a desired attribute in certain aged cheeses to a major defect in others.

Stated simply, crystals in cheese occur when the concentration of a product (such as a salt like calcium lactate or an amino acid like tyrosine), exceeds the maximum solubility within the moisture phase of a cheese. When this imbalance occurs, crystals form and grow, leading to white dots within the interior or white lines or spots on the exterior.

Crystal texture ranges from moderately soft crystals (caused by calcium lactate) to hard, discrete bright white crystals (calcium phosphate complexes). They can be grainy/gritty (tyrosine) or sandy (lactose).

Defects in Cheddar

The most common crystal defect in aged Cheddar cheese is calcium lactate. This crystal develops from soluble calcium derived from the protein-bound calcium phosphate that is solubilized/released over the first month of cheese ripening, and lactate derived from the fermentation of lactose by starter cultures. Accelerated by temperature abuse, excessive residual lactose in the cheese and moisture accumulation within the package, calcium lactate crystal formation is often seen in products where the packaging is loose along a rough surface or cut edge.

The moisture phase in cheese contains both calcium and lactate. Thus, moisture movement facilitates the transport of calcium and lactate to existing crystals, which allows these crystals to grow and become visible to the consumer.

Use of cheese milk with very high lactose content (e.g., too much fortification with nonfat dry milk powder or condensed milk) can contribute to this defect due to the eventual fermentation and accumulation of excessive lactate. It usually takes three to four months before you may observe calcium lactate crystals, and lower-moisture cheeses can be more prone to this defect.

There are other components in the cheese moisture phase (e.g., phosphates) that can also bind soluble calcium, so sometimes calcium lactate crystals are not observed even though it may appear that the concentrations of calcium and lactate should be high enough for crystal formation. Steps that are often taken to avoid this defect include: avoiding excessive lactate levels in cheese (such as washing or rinsing the curd), removing more calcium during cheese manufacture (thus less is left in cheese to form crystals), tight packaging of cheese and avoiding conditions that cause cheese to release moisture (low pH, warm temperatures including heat generated by light exposure).  In addition to these known solutions, the Wisconsin Center for Dairy Research has also been investigating the potential use of membrane filtration to help control this issue.

Tyrosine crystals

Another common crystal defect is tyrosine, an amino acid with poor solubility whose crystal formation is linked with the use of Lactobacillus helveticus, a bacterium used as a starter in harder Italian, Dutch and Swiss cheeses. Tyrosine crystals usually take months to develop.

Tyrosine crystals are generally much harder and more discrete. They can form in the interior or exterior of the cheese. A desired attribute in hard Italian cheeses, consumers often look for these gritty white crystals as the sign of a properly aged cheese. In Cheddar, however, tyrosine crystals are considered a defect, especially when the cheese is used to produce processed cheese.

At this time, the best solution is to eliminate the use, or reduce the levels, of Lactobacillus helveticus strains capable of accumulating tyrosine. This solution is not always desirable as it also causes a reduction in the desired flavor development of the cheese. Other suggestions include using lower cheese ripening temperatures and avoiding cheese sweating.

Processed cheese can also face challenges related to crystal formation. In particular, excessive use of emulsifying salts such as sodium citrates or sodium phosphates or the addition of high levels of whey can lead to solubility concerns.

Trisodium citrate is a popular emulsifying salt but it can form calcium citrate crystals or a “white haze” or “bloom” if excessive amounts are used. Similar issues can occur with the use of disodium phosphate. Processed cheese makers must carefully regulate the concentrations of these two types of emulsifying salts and their ratios if used together. Cheese makers should also avoid very high pH values, since calcium crystals are less soluble at high pH.

 Don’t overlook the value of educating cheese mongers, grocery store managers and other members of the distribution chain about the role of proper cheese handling as well as explaining the fact that tyrosine crystals are a desired attribute in certain aged varieties. They can then address consumer questions and avoid any misunderstanding regarding crystals in cheese.