The microbes that give cheddar cheese its distinct flavour

The nutty, creamy flavour of cheddar cheese varies slightly according to a delicate balance of bacteria, which has now been identified by scientists. Understanding how these bacteria interact could help cheese-makers achieve the specific flavour they are aiming to create or even lead to computer simulations that formulate starter cultures with the correct balance of microorganisms.

All fermented food and drinks – including cheese, kimchi and kombucha – rely on complex interactions between microorganisms. To make cheese specifically, starter cultures are added to milk to kick-start fermentation and acidify the dairy, leading to a slightly tangy taste.

Cheese-makers have long known that some of the key bacteria involved in this process are Streptococcus thermophilus and types of Lactococcus, but little was known about how these interact and if those interactions influence a cheese’s flavour.

Chrats Melkonian at Utrecht University in the Netherlands and his colleagues focused on cheddar as it is one of the world’s most popular cheeses.

They produced different cheese samples using four starter culture variations. One came from industrial producers of such starters and contained both S. thermophilus and types of Lactococcus, mainly the species L. lactis and its subspecies L. cremoris. The others were made by the researchers and contained either the same bacteria as before, no S. thermophilus or no types of Lactococcus.

One year later, the team found that the cheese made from the starter without S. thermophilus had much lower populations of types of Lactococcus than the others, even the starter without any Lactococcus types to start off with. This suggests S. thermophilus is important in enhancing Lactococcus growth, says Melkonian.

When it comes to flavour, L. cremoris seems to regulate the development of the chemicals diacetyl and acetoin, which provide a buttery flavour, but can lead to an “off” taste when there is too much of them.

L. cremoris also increased the concentration of compounds that add subtle meaty and fruity notes, the researchers write in their paper. In the absence of the subspecies, the cheeses tended to have higher levels of chemicals that add hints of nutty and creamy flavours.

There was no difference in microbial activity or taste in the cheeses that used the same starting bacteria, regardless of whether the starters were made industrially or by the team.

Overall, these findings indicate that the flavours within cheddar cheese are easily influenced by the interactions of different bacteria. This could help cheese-makers tweak the taste of the cheese they are creating, says Melkonian. “We now have targets of which interactions could affect different bacteria.” Computer simulations could even be used to formulate a starter with the correct proportion of different bacteria for a desired flavour, he says.