Peptides that form during the aging of cheese are essential for producing the robust flavor found in mature cheeses, known as kokumi. A research group from the Leibniz-Institute for Food Systems Biology at the Technical University of Munich has developed a new method that allows for the accurate, rapid, and efficient analysis of these important flavor peptides. The team has also established a database, based on over 120 cheese samples, which could predict how flavor evolves during the cheese aging process.
The word “kokumi” comes from Japanese and describes a rich and lingering taste experience. This flavor sensation is especially strong in aged cheeses, primarily because of the rising levels of gamma-glutamyl dipeptides, which are tiny molecules formed from glutamic acid and another amino acid.
Researchers classify dipeptides into categories such as gamma-, alpha-, and X-glutamyl based on the type of linkage between the amino acids; however, only gamma-glutamyl dipeptides contribute to the kokumi flavor. The distinct polarity of these dipeptides and their structural similarity to other flavor compounds make their analysis challenging in the field of food science.
Advanced Analysis Technique Developed
Despite these challenges, Principal Investigator Andreas Dunkel and his team have created an advanced method using ultra-high performance liquid chromatography-mass spectrometry. This technique can accurately identify the concentrations of all 56 types of gamma-glutamyl dipeptides in just 22 minutes. Improved sample preparation allows for the analysis of 60 cheese samples in a single day.
“This marks a major advance compared to previous methods. Our findings demonstrate that our technique is quicker, more effective, and dependable — it yields reproducible results and can detect even very low concentrations,” explains Sonja Maria Fröhlich, the lead author and a Ph.D. student at the Leibniz Institute. To further explore how ripening duration impacts gamma-glutamyl dipeptide levels, the researchers applied this method to 122 cheese samples from both Europe and the United States after their initial testing phase. The ripening periods for the cheese varied from two weeks to 15 years.
Mold Cultures Enhance Flavor Development
The data indicates that, as anticipated, higher cheese maturity leads to elevated levels of glutamyl dipeptides. “Interestingly, incorporating blue and white mold cultures significantly boosted gamma-glutamyl dipeptide levels, even with shorter maturation periods,” notes Andreas Dunkel, who leads the Integrative Food Systems Analysis research group at the Leibniz Institute.
According to the food chemist, “The concentration patterns we’ve identified at various ripening stages and across different cheese varieties can serve as a future database for predictive models. These models might, for instance, help objectively track flavor changes during cheese maturation, reduce ripening times, or devise new plant-based cheeses that appeal to consumers.”
“Through an interdisciplinary approach grounded in food systems biology, one of our objectives is to merge our analytical findings with bioinformatics to create predictive models that can enhance sustainable food production,” concludes Veronika Somoza, director of the Leibniz Institute.
