New discoveries could improve cheese production and safety, lead to novel cheeses

As cheese ages, beneficial bacteria degrade proteins and lipids (from milk fat) and produce the molecules responsible for characteristic aromas of ripening cheeses. (1) The diversity of "non-starter" bacteria, which spontaneously develop during ripening and form flavor compounds, is the key factor for developing the characteristics of cheese.

The role of microorganisms in flavor formation had not been fully understood, "due to the diversity of cheese varieties and the complexity of cheese microbial consortia," said corresponding author Morio Ishikawa, Ph.D., a professor at the Department of Fermentation Science, Faculty of Applied Bioscience at the Tokyo University of Agriculture in Japan.

In the study, the investigators presented an approach to identifying and examining certain bacteria known to be involved in cheese production, including 3 phyla of bacteria, Firmicutes, which are lactic acid bacteria, and Actinobacteria and Proteobacteria, which produce characteristic flavors in certain cheeses. By comparing bacteria from across the 3 phyla to other known flavor-producing bacteria in a cheese ripening test, the researchers showed a relationship between specific microbes and flavor.

Ishikawa and his collaborators had used statistical analysis to reveal relationships between bacterial types and the various volatile flavor-producing organic compounds that each produces in surface-mold ripened cheeses. To test that relationship of specific microbes to flavor, they then selected non-starter bacteria of taxa that were strongly correlated with specific volatile compounds and flavors, and performed cheese-ripening tests. These tests showed that the bacteria from the correlational research were in fact responsible for the flavors of the cheeses.

Additionally, this research could provide a scientific basis for improving the safety and quality of cheese. "By isolating and investigating microorganisms involved in flavor formation as targets, rather than blindly examining them, we will be able to scientifically evaluate the safety of these microorganisms. At the same time, it may be possible to construct a cheese production method that uses only those microorganisms that play a major role in flavor production," said Ishikawa.

"The comprehensive insights into the complex associations between microbiota and flavor improve our systematic understanding of mechanism of cheese flavor production," said Ishikawa. The new research will not only provide a scientific basis for the traditional method of cheese production, but might also enable the creation of novel cheeses.

1. per Ishikawa, little or no lactose remains in cheese during ripening.