Alternative title: Fat is Flavor!
One of the key flavor formation pathways is the enzematic hydrolysis (lipolysis) of triglycerides. Okay, let’s break that statement down into it’s basic parts: A triglyceride is a molecule that is composed of a glycerol with three fatty acids. Enzematic hydrolysis, or lipolysis, is the breakdown of lipids – of which, triglyceride is one – that cleaves the bonds between the glycerol and its fatty acids. Since this is enzematic hydrolysis, the enzymes lipase and esterase are catalysts that help speed up this reaction. So, through the speedy separation of glycerol and fatty acids aided by lipase and esterase, the fatty acids are removed from the triglyceride and it is these fatty acids that cause the various flavors we perceive in cheese. Once these fatty acids are removed from the glycerol, they are called free fatty acids.
Lipolysis = Triglycerides (glycerol + 3 fatty acids) + lipase/esterase enzyme = free fatty acids = TASTY GOODNESS!!
Cool! But there are so many flavors in cheese – how do free fatty acids create them all?
A fatty acid is made up of a carboxyl group and, more importantly for our purposes, a hydrocarbon ‘tail’. Free fatty acids found in cheese have short-chain hydrocarbon tails that consist mainly of 4, 6, 8, or 10 carbons. Short-chain fatty acids provide desireable piquant flavor and aroma in many cheeses. The fat in sheep’s milk and goat’s milk contains higher concentrations of short-chain fatty acids than that in cow’s milk. Because of this, some sheep and goat cheeses attain a more peppery, piquant flavor and aroma profile than their cow’s-milk counterparts.
Further reactions of the fatty acids (such as oxidation) cause various specific flavors produced by different fatty acid flavor derivatives: ethyl esters (fruity aromatic notes, floral, goaty), thioesters (cheesy, cooked vegetable), branched chain keto acids (pungent cheesy), and unsaturated alcohols and ketones (mushroom-like). N-Methyl ketones, prduced by partial beta-oxidation of fatty acids, are of particular importance to blue cheese flavor.
An experiment published in The Journal of Dairy Science analyzed the flavors of various cheeses and the number and type of free fatty acids found in each one. The results are quite interesting:
Port Salut and Monterey Jack are two semisoft cheeses with similar flavor characteristics – they are mild and milky although the Monterey Jack cheese had a slightly more sharp, diacetyl-like flavor. Interesting to note is that their flavor characteristics are similar and their free fatty acid profiles were also similar. And, of the cheese varieties analyzed, these two cheeses were among the lowest concentrations of free fatty acids.
Limburger cheese, known for it’s strong taste and stronger smell, contained some of the largest amounts of 4 and 6 chain carbon free fatty acids among the soft and semisoft cheeses. Gruyere also contained relatively high concentrations of 4 and 6 chain free fatty acids.
Gjetost and goat’s milk cheeses both contained goat’s milk fat, but the caramelized Gjetost exhibited only a mild goaty flavor. The Gjetost probably contained some cow’s milk, whereas the goat’s milk cheese was manufactured with only goat’s milk, which accounted for its higher concentrations of 8 and 10 chain free fatty acids and stronger goaty flavor.
Look at how many more 4, 14, and 16 carbon chain free fatty acids brie has compared to camembert! On the other hand, the French Roquefort and the U.S. blue are awfully similar in the total amount of free fatty acids.
Of course, terroir and breed of animal affects the flavor as well, perhaps introducing a different concentration of free fatty acids into the cheese, but that is a topic for next time.
(1) Jelen, Henryk. Food Flavors: Chemical, Sensory and Technological Properties. CRC Press, 2012
(2) Kindsedt, Paul, Vermont Cheese Council. American Farmstead Cheese: The Complete Guide To Making and Selling Artisan Cheeses. Chelsea Green Publishing Co., 2005
(3) Woo, A.H., Kollodge, S., Lindsay, R.C., Quantification of Major Free Fatty Acids in Several Cheese Varieties. Department of Food Science, University of Wisconsin-Madison, 22 February 1983 http://download.journals.elsevierhealth.com/pdfs/journals/0022-0302/PIIS0022030284813806.pdf
Journal of Dairy Science Volume 67, Issue 4 , Pages 874-878, April 1984
(4) Friberg, Stig., Hui, Yiu H., Handbook of Food and Beverage Fermentation Technology. Taylor & Francis e-library, 2005