Since the beginning of cheese making, the preservation of the fresh cheese surface has always been a major concern after the cheese has left the brine bath or dry salt table. Then, someone had the idea of coating the surface with the fine gray ash that was readily available from burnings. In earlier times, this was ash from the burning of the grapevine clippings in the Loire Valley of France, which was even then noted for their wealth of fresh goat cheese.
This seemed to preserve the cheese by discouraging the insects, microbes, and mold spores from setting up housekeeping. It also soon became apparent that the ash tended to dry off the surface as well.
The ash applied to cheese once came directly from a fire but is now mainly made from salt and vegetable ash (vegetables that are dried and turned into ash). The ash is sterile, odorless and tasteless.
Aesthetic and Practical Reasons
Many folks may look at this ash/charcoal addition and say: "I am not interested in eating dirt with my cheese." The reality is that this is not barbecue charcoal or gritty ash. It is a finely powdered, food-grade component actually revered by the medical world for its ability to control and absorb toxins.
Ash is used in cheesemaking for both aesthetic and practical reasons. It is as much about tradition as it is the science of cheesemaking.
A line of dark ash running down the middle of a cheese is visually stunning. Humboldt Fog from California and Morbier from France are cheeses that use ash in this way. French goat cheeses that are pure white in the middle with a dark ash rind, such as Valencay and Selles-sur-Cher, use ash partly for a visual statement, too.
Used on the outside of a cheese, ash helps form a thin rind. This can be seen on cheeses like the Italian cheese Sottocenere al Tartufo and the French Saint Maure. Long ago, ash was also used to protect the inside of cheeses, such as Morbier. When making this cheese, the cheesemaker would pour leftover curds into a mold and cover the curds with a thin layer of ash to protect it from flies until the cows were milked again and more cheese could be made. Now, Morbier is made from one milking, but the traditional line of ash remains.
Acidity in cheese can inhibit ripening, preventing cheese from reaching its optimal flavor and texture. Ash is an alkaline substance that neutralizes acidity and aids in the ripening process. Many of the French goat cheeses are examples of using ash in this way.
The vegetable ash helps to neutralize the surface pH of the cheese. When making bloomy rind cheeses at home, such as camembert/brie, ash can lengthen the aging period without seeing excess mold growth on the rind itself.