Why Are Cheeses Made with Ash? | The Cheese Professor

Humboldt Fog with fruit photo courtesy Cypress Grove

Ash-ripened cheeses are among the most instantly recognizable in the dairy canon for their somewhat goth exteriors, or telltale, racy stripes, especially when set against the bright white paste of young goat cheeses. Perhaps second only to blue cheeses, and sometimes mistaken for blue cheeses, ash-ripened cheeses demand attention for their visual intrigue from cheese experts and novices alike. Ash is much more than just a cute look, though, as ash has transformative qualities that can greatly affect the outcomes of the cheeses it helps to ripen.

Josh Windsor, Associate Director of Caves for Murray’s Cave Aged Cheese program, deals regularly with ash first-hand, in the ripening of several Loire Valley goat’s milk cheeses for Murray’s: Valençay, Selles-Sur-Cher, and Sainte Maure. (Murray’s works in partnership with dairies around the world to take unaged cheeses and finish them in a manner similar to that which they would experience in their places of origin.) Windsor talks to us all about ash: its history, character, application, and regulation.

What Kind of Ash is in Cheese?

Ash is the result of burning plant matter such as wood, leaves, vegetables, etc., at an extremely high temperature. “What’s leftover is the stuff that doesn’t burn away,” says Windsor, “mostly the mineral content of it, which is predominantly carbon,” and whatever else the carbon is holding onto. Ash can go by a number of different names — vegetable ash, charcoal, carbon — which are all relatively the same thing. Activated charcoal, or activated carbon, is also related, but with an additional step: “activated charcoal involves an oxygen flush to knock away everything else that carbon that carbon might hold onto,” says Windsor, leaving just carbon and oxygen, and is typically not used in cheesemaking.

While the ash that was used in cheesemaking of yore may have been collected from the hearth of one’s kitchen, modern, commercial ash is a much more controlled product. “We use ash purchased from a cheese supply company,” says Windsor, “and we do what's called liquid ashing, which is actually an ash that is held in a solution. Other cheesemakers may use a dry ash, but for our facility we have a lot of air movement, so using a fine ash powder is not great.” Vegetable ash is flavorless, and neither contributes a discernible texture unto itself, other than the texture it helps to encourage in certain cheeses.

The History of Ash in Cheesemaking

“All food origin stories have legends surrounding them,” says Windsor, and ash has an oft-repeated one when it comes to cheesemaking. The common thinking regarding ash was that it was used as a preservative, or insect repellent, between the collection of different batches of milk. Ash would be sprinkled on top of milk, or even curds, to protect them while additional milk was collected before the entire batch went on to the rest of the cheesemaking process.

Cheeses that have a stripe of ash running through the middle of the paste, such as Morbier, rather than an ash-coated exterior, are especially believed to represent two separate milkings: the evening milk and morning milk, with one protected by the layer of ash until enough additional milk was collected for cheesemaking, with the cheese maintaining this layering through to completion.

As for other lore surrounding ash-ripened cheeses, there is reason to believe not all ash necessarily came from the homestead hearth. “If you look at certain regions, there was a big charcoal industry around Burgundy, for example, because of their burning all the old vines for potash,” says Windsor, which created ideal conditions for growing mustard in Dijon. “So ash might have actually been kind of industrial depending on what was going on in the area.”

How Does Ash Ripening Work?

The primary function of ash in cheesemaking is to raise the pH of the surface of various cheeses in order to create a beneficial environment that encourages certain types of microbes. “I often think of it as adding lime to soil for particular plants to grow,” says Windsor. “It's the same kind of process; you're getting the exact pH range on the surface of the cheese to select for the microbes that you want.”

In its natural state animal milk is only slightly more acidic than neutral, whereas ash is basic, but acid-set cheeses, such as the Loire Valley cheeses Windsor ages, undergo an acidification of the milk to coagulate the curds, lowering their pH. “Geotrichum candidum, which is that mottled, brain-like, labyrinthine, beautiful microorganism that grows on those particular styles of cheese, does not like an acidic environment,” says Windsor. “It needs a more neutral environment in order for it to flourish and sporulate. So the ash kind of conditions the surface of the cheese, in order to allow that microbe to grow.”

While ash-ripening is often synonymous with Loire valley goat’s milk cheeses (and the American cheeses they have inspired,) ash is not limited to goat’s milk, nor only to young, soft cheeses. Morbier is a cow’s milk cheese, for example, and ash may also be used for firmer, aged cheeses or even blue cheeses.

Exterior Ash Versus Interior Ash

What then, of those cheeses that have an internal stripe of ash, where less microbial activity is participating in the ripening of the cheese, rather than an outer coating? According to Windsor, modern iterations of Morbier, or contemporary ash-striped cheeses such as Humboldt Fog, (which has both internal and external ash,) may actually be more about aesthetics. (But we don’t blame them, since they’re gorgeous.) “These days, it's just a nod to a tradition,” he says. “It doesn't serve as much of a functional role as it does on the exterior of the cheese.”

Modern Considerations with Ash

As with many elements of cheesemaking that have been going on in Europe for centuries, if not millennia, (raw milk and cheese mites come to mind,) ash also had to have its moment with the U.S. FDA. During a period from 2014 to 2016, the FDA prevented the import of ash-ripened cheeses, classifying ash as a “non-permitted colorant.”

“That's actually how Murray’s got into the ash-aging business,” says Windsor, citing that while ash-ripened cheeses were prevented from being imported for a time, the consumption and sale of vegetable ash was not similarly halted. “So we were purchasing the cheeses pre-ash in France, and then aging them ourselves.”

After a period of discovery, ash was deemed GRAS — “Generally regarded as safe” — by the FDA, and ash-ripened cheeses were again permitted entry into the U.S., hopefully forevermore.

Ash Cheeses

There are many ash cheeses, these classics are some of our favorites.

Morbier

Morbier is a French aged raw cow's milk cheese made with vegetable charcoal. It is matured for 45 days, develops a rich, grassy flavor, and is a pale yellow with a distinctive stripe down the middle. It has been an AOC cheese since 2000 and received a PDO in 2002. While legend says the cheese was created by a gust of wind spreading ash, in truth ash was used to protect the evening's curd, then when the cheese was layered with fresh curd it formed a stripe.

Valençay

A pasteurized goat's milk cheese from the Loire Valley that ages for 3-5 weeks, Valençay is an AOC cheese coated in ash and then develops penicillium candidum bloomy mold. Legend says it was once made in a true pyramid shape but when Napoleon suffered defeat in Egypt he sliced off the top of the cheese and it was made this way ever since then, however local cheesemakers claim the distinctive pyramid shape was inspired by local cheese steeples. It has a very dense structure and a lemony tang and milky flavor.

Humboldt Fog

Cypress Grove's Humboldt Fog is a distinctive soft ripeened goat milk cheese that was dreamed up by cheesemaker Mary Keehn. The line of vegetable ash connotes fog. Ash is also used just under the rind. It's aged for 4-5 weeks and is a frequent award-winner. Made in Northern California, it has herbal and citrus notes and is one of the best-known original American artisan goat cheeses. Read more about Cypress Grove.