Jacinta Bowler
Jacinta Bowler is a science journalist at Cosmos.
They were published in the Best Australian Science Writing 2023.
I have terrible news. Those nutty, buttery, fruity, and creamy flavours that makes cheese so delicious have upsetting origins – microbes.
But that’s not the end of the story. A new study out of Europe has spent a whole year making different versions of cheddar cheese to discover which bacterium provide which flavours.
“Cheese fermentation and flavour formation are the result of complex biochemical reactions driven by the activity of multiple microorganisms,” the researchers write in their new paper, published in Nature Communications.
“Here, we studied the roles of microbial interactions in flavour formation in a year-long Cheddar cheese making process, using a commercial starter culture containing Streptococcus thermophilus and Lactococcus strains.”
Cheese making is a long process, and for the researchers it started with warm milk inside a 150 kg vat. To make cheese you need to add a starter culture – coagulants and the microbes.
The researchers took all of the strains and added them into two of the vats, preparing one of them under industrial conditions, and one of them by hand. The third vat they added all but the blend of L. lactis and L. cremoris and the fourth vat they added all but the Streptococcus thermophilus.
Then, after packing the cheese into blocks, the researchers then waited a whole year.
“The cheeses were vacuum-packed and stored at 9°C until sampling,” they wrote in the paper.
“Following the acidification phase, we sampled the resulting cheddar cheeses in 5 time points over the one year period.”
The researchers found that both bacteria had important roles, but Streptococcus thermophilus was particularly required.
“S. thermophilus has a crucial role in boosting Lactococcus growth and shaping flavour compound profile,” they write.
“While S. thermophilus had large contribution to the flavour profile, Lactococcus cremoris also played a role by limiting diacetyl and acetoin formation, which otherwise results in an off flavour when in excess.”
This flavour profile was undertaken not by eating, but by genome sequencing, and sampling the compounds in the cheese.
“Our results show how strain-specific metabolic interactions between microbes shape the biochemical profile of cheese, and provide targets towards the rational design and assembly of microbial communities with the aim of fine-tuning cheese flavour,” the team conclude.
“More broadly, the study provides a blue-print to uncovering in situ interactions in complex food microbial ecosystems.”