Lactic Acid Bacteria (LAB) Starter Cultures

"Cheese making cultures are good bacteria who’s job is to grow and work within the milk to consume lactose and convert it into lactic acid, hence the LAB (lactic acid bacteria) designation. This process is done through fermentation.

Starter cultures are very specific in their tasks and need to have a healthy population so they are more competitive than undesirable (or unhealthy) bacteria that could contaminate the milk, curds or cheese.

Varying strains of LAB starter cultures will determine the final results of a finished cheese.

Once the Lactose has been converted there is minimal food remaining for the bacteria to sustain their population. But, even as the bacteria begin to die off, their work is not done.

As the bacteria die their cell structure breaks down and very specific enzymes are released into the cheese. These enzymes can contribute many good things to the cheese including diacetyl which adds a butter-like flavor, or small amounts of CO2 which creates a more open cheese body. Overall the enzymes can contribute to the development of aromatics, flavors, and varying textures of the cheese while it ages.

Note: Without converting lactose, in the milk, to lactic acid the final cheese can, in the worst case, be unhealthy to eat. This is because leftover lactose can provide food for bad microbes to populate"

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Mesophilic Starter Cultures:

Mesophilic starter cultures are bacteria that do their best work in more moderate temperatures, as opposed to hotter temperatures. “Meso” means middle, or in between. The bacteria in mesophilic culture works at a range of 62-102F and is happiest between 84-86F. At lower temperatures mesophilic can stop working and may not be able to outcompete non-dairy bacteria which may cause off flavors to develop. If the temperature moves to the higher end of this range, mesophilic will become less efficient at converting milk sugars, and at 102F or higher mesophilic will die off quickly.

Popular examples of cheese that rely on this style of starter culture include Cheddar, Colby, Chèvre, Feta, Brie, Camembert, Havarti and Blue.

The bacteria strains found in basic mesophilic cultures are:

  • Lactococcus lactis subsp. lactis
  • Lactococcus lactis subsp. cremoris

Thermophilic Starter Culture:

Thermophilic starter cultures are bacteria that do their best work in the higher temperatures. “Thermo” refers to its preference for heat.The bacteria in thermophilic culture works at a range of 104-112F, to some degree it will also work down into the mid 90s and up into the 120s. Some thermophilic strains continue to work after the the cheese is in its aging space.

Popular cheeses that rely on this style of starter culture include: Mozzarella, Parmesan

The bacteria found in basic Thermophilic cultures are:

  • Streptococcus thermophilus
  • Lactobacillus helveticus
  • Lactobacillus delbrueckii subsp. lactis

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