Cheese Aging and Umami
Aging is a crucial step in developing unique flavors and enhancing umami characteristics in cheeses. During the aging process, several chemical and biochemical changes occur, resulting in the accumulation of umami amino acids.
The chart below illustrates the progressive increase of amino acids in cheddar cheese during the aging process. Over an 8-month period, the total amino acid content rises from 48mg/100g to 1,001mg/100g. Notably, the umami amino acids Glutamate (Glu) and Aspartate (Asp) experience significant growth, going from 11mg/100g to 182mg/100g and from 3mg/100g to 43mg/100g, respectively. This rise in umami amino acids contributes to the enhanced savory taste and flavor profile of aged cheddar cheese.
Glycolysis
Cheeses are in general made by fermenting milk with lactic acid bacteria (LAB). These bacteria convert lactose (milk sugar) into glucose and galactose, which are then metabolized through glycolysis to produce lactic acid. Lactic acid contributes to the tangy flavor and helps lower the pH (i.e. add to the acidity) of the cheese. The increased acidity hinders the growth of harmful organisms, thereby preserving the cheese.
Coelho, M. C., Malcata, F. X., & Silva, C. C. (2022). Lactic acid bacteria in raw-milk cheeses: From starter cultures to probiotic functions. Foods, 11(15), 2276.
Proteolysis
Proteolysis refers to the breakdown of proteins into smaller peptides and amino acids. Proteolysis takes place in three stages: the breakdown of proteins in milk prior to cheese production, the enzymatic coagulation of milk, and the breakdown of proteins during cheese maturation. The third one, proteolysis during cheese aging is the most substantial. Enzymes naturally present in the cheese, as well as those produced by the starter cultures, gradually break down the proteins during aging. This process releases various amino acids, including glutamate and aspartate, which are key contributors to umami taste, among others.
Fox, P. F. (1989). Proteolysis during cheese manufacture and ripening. Journal of dairy science, 72(6), 1379–1400.
Maillard Reaction
The Maillard reaction, occurring between amino acids (as amino acid itself, peptide, or protein) and reducing sugars, contributes to the development of complex flavors and aromas in aged cheeses.
Citrate utilization
Citrate, a naturally occurring compound present in milk, serves as a substrate for bacteria to generate flavor compounds. As cheese matures, bacteria metabolize citrate and produce diacetyl, which imparts a delightful buttery taste to certain cheeses.
McSweeney, P. L., & Sousa, M. J. (2000). Biochemical pathways for the production of flavour compounds in cheeses during ripening: A review. Le Lait, 80(3), 293–324.
Lipolysis
Lipolysis refers to the enzymatic breakdown of fats into fatty acids and glycerol. In the context of cheese, lipolysis plays a crucial role in the formation of flavor compounds, including free fatty acids (FAAs), which significantly contribute to the overall taste and aroma of the cheese.
Comparison of Amino Acid Composition
Different cheeses undergo varying aging processes, leading to diverse flavor profiles and variations in amino acid compositions. The aging of cheeses is a complex process influenced by factors such as cheese type, production techniques, aging conditions, and microbial activity. Each cheese type has a unique set of enzymes and microorganisms that contribute to the breakdown of proteins and the subsequent release of amino acids.
As cheeses age, proteolysis occurs at different rates, resulting in variations in the types and quantities of amino acids present. For example, some cheeses, like Parmesan, undergo extended aging periods, allowing for extensive proteolysis and the accumulation of amino acids such as glutamate, which contributes to their highly concentrated umami flavor. In contrast, fresher cheeses like mozzarella have shorter aging times, resulting in lower levels of amino acid development. The diversity in cheese aging processes leads to a wide range of flavors and umami characteristics, making each cheese a unique culinary experience.
Cheddar
Cheddar cheese is a natural cheese which originates from the English village of Cheddar in Somerset, while it is widely produced in former British colonies. We have two sample data for cheddar, from the UK and the US, aged for 8 months and 10 years respectively. The top three amino acids for the aged products are Leucine (Leu), Glutamine (Glu), and Lysine (Lys). While Leucine does not have distinguishable taste or flavor, it leads to aromas of sweet chocolates or typical baked cheese after Maillard reaction (in this article glucose is assumed as the reducing sugar) at different temperatures (100 °C / 212 °F and 180 °C / 356 °F). Lysine is said to contribute to salty taste with some bitter components, and its Maillard reaction aroma at a high temperature is associated with toasted bread.
Both the British and American cheddar cheese samples are in line in terms of amino acid compositions, with 8-month and 1-year aged products from those two origins showing similar profiles. The growth rate of Glu looks to be higher in the long term than Leu, and Glu content of US cheddar cheese aged for 10 years is substantially higher than any other amino acids.
Fourme d’Ambert
Fourme d’Ambert is a semi-hard French blue cheese, inoculated with Penicillium roqueforti and produced in Auvergne, central France. While the cheese shares the same top three amino acids of Glu, Lys, and Leu, the amino acids are more equally distributed than other cheeses. Glu accounts for only 12.5% of total amino acids in Fourme d’Ambert, whereas its share in other cheeses averages around 20%.
Gouda
Gouda is a sweet, creamy cow milk cheese from Netherlands, aged up to 3 years. Its amino acid compounds have Valine (Val) and Phenylalanine (Phe) as close third and fourth majority. Phe can create a sweet taste that is 100 to 200 times sweeter than sucrose when combined with aspartic acid (Asp), which is included in Gouda (18mg/100g in 4-month aged). With Maillard reaction, Val leads to aromas of rye bread and spicy chocolate at low/high temperatures, while Phe provides floral aromas of viola or lilac at different temperatures.
Parmigiano Reggiano
Parmigiano Reggiano cheese exhibits the most pronounced umami flavor compared to other types of cheeses. It is an hard, granular cheese produced from cow milk and aged at least 12 months made in Parma and Reggio Emilia, Italy. Even before aging, Glu content of 1,180mg/100g is higher than any other cheese discussed in this article. It rises to 2,220 mg/100g after 4 years of aging. Proline (Pro) in the third place carries minerally, salty, and sour tastes and generates a certain burnt protein smell and aroma of bread after Maillard reaction at low/high temperatures.
In aged Parmigiano Reggiano cheese, you may notice the presence of crystallized portions within the cheese. These crystallized parts exhibit a highly concentrated amino acid profile that sets them apart from the surrounding areas of the cheese. Specifically, within the crystal part of Parmigiano Reggiano, amino acids make up a significant portion, accounting for approximately 28g out of 100g. Among these amino acids, Leu, Isoleucine (Ile), Val, and Methionine (Met) contribute 9g, 6g, 3g, and 2g respectively. It is worth noting that Ile shares a similar taste and flavor profile with Leucine. On the other hand, Met imparts a metallic and minerally flavor and, when subjected to the Maillard reaction, gives rise to an aroma reminiscent of potatoes.
