How Microbes Craft Cheese Flavors

Humans mastered the art of cheese fermentation over thousands of years. Although researchers knew that some bacterial species were key to cheesemaking, they knew little about the microbial community interactions that occurred as milk turns into cheese.¹ 

After conducting a year-long experiment, researchers led by Ahmad Zeidan, a bioengineer at Chr. Hansen (now Novonesis), cracked how these microbial interactions affect cheese flavor formation.² Their findings, reported in Nature Communications, could help cheesemakers finetune cheddar characteristics. 

The team chose cheddar cheese as a model system because its composition of 25 to 30 bacterial strains provided an intermediate level of microbial complexity to work with, Zeidan explained. They then assessed the effects of specific bacterial strains on cheese flavor by removing either a single strain or a group of strains from the starter culture. 

The presence of Streptococcus thermophilus was essential for the growth of the Lactococcus bacterial population. Metatranscriptomic and metabolic modeling of controlled milk fermentation experiments revealed that S. thermophilus acts as a key amino acid donor to the Lactococcus community, alleviating nitrogen limitations that may occur during cheese ripening.

Metatranscriptome analyses also revealed that one Lactococcus cremoris strain made cheddar taste good by limiting the formation of compounds that, when in excess, lead to off flavors.³ When the team took a closer look at the Lactococcus community, they found that competition between L. cremoris and another Lactococcus strain drove the formation of these compounds.

“This work advances the field [by] figuring out what needs to be done to make cheese taste the way we want it to taste,” said Maria Marco, a microbiologist at the University of California, Davis, who was not involved in the research. “It [also] shows the complexity of microbial environments. We're not just talking about different species, but different strains of the same species interacting with each other.”