The terms sharp and mild refer to the flavor of cheddar cheese. The sharper the cheddar, the more tangy and complex it will taste. Marianne Smukowski, who heads up safety and quality applications at the Wisconsin Center for Dairy Research, says the term sharp is a marketing phrase that doesn’t coincide with any guidelines or grades within the U.S. dairy industry. She says sharp cheddar is simply an aged piece of cheese, probably six to nine months old, while extra-sharp cheddar is likely one-and-a-half to two years old.

Joe Widmer, a Wisconsin cheesemaker whose six-year-old cheddar placed first in the 2007 American Cheese Society awards, says “the older [the cheese] gets, the more the bacteria produce enzymes that break down its fats and proteins. The process produces compounds that give the distinct cheddar flavors—almost beefy and nutty. I know people that get a supersharp piece of cheddar and compare it to a piece of meat or steak.”

Marc Druart, a master cheesemaker at the Vermont Institute for Artisan Cheese, adds that the starter cultures, salt, and moisture content of the cheese have to be balanced for it to age properly. Each variable affects the breakdown of the fats and proteins—which form the compounds that give the cheese a sharp taste (aldehydes and alpha-keto acids) and other flavors (esters).

“As any cheesemaker will tell you, this is not an exact science,” says John Spencer, managing director of the Cheddar Gorge Cheese Company in Somerset, England. “If we were to use our exact recipe, methods, equipment, and even the same people, but change our location and source of milk, we would make a slightly different cheese.”