How Blue Cheese Is Made

Stilton and Shropshire blue
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Blue cheese is thought to have been invented by accident when a drunken cheese maker left behind a half-eaten loaf of bread in a moist cheese cave. When he returned back, he discovered that the mold covering the bread had transformed the cheese into blue cheese.

"Blue Vein cheeses," also called blue cheese, is a generic term used to describe a cheese produced with cow's milk, sheep's milk, or goat's milk and ripened with cultures of the mold Penicillium. The final product is characterized by green, gray, blue, or black veins or spots of mold throughout the body. These veins are created during the production stage when cheese is "spiked" with stainless steel rods to let oxygen circulate and encourage the growth of the mold. This process also softens the texture and develops the distinctive blue flavor.

How Blue Cheese Is Made

The process of making blue cheese follows the same six standard steps used to make most types of cheeses:

  1. Acidification
  2. Coagulation
  3. Curds and whey
  4. Salting
  5. Shaping
  6. Ripening

Where do those blue/green streaks come from? The unique look of blue cheese is a result of a specific type of mold added during the cheesemaking process and an additional step in the aging process called “needling."

Beneficial Bacteria

The most widely used molds in blue-veined cheeses are Penicillium Roqueforti and Penicillium Glaucum. These fungi are found commonly in nature and were “discovered” by cheesemakers aging their cheeses in damp, cool caves.

Exactly when this helpful bacteria is added during the cheesemaking process depends on the type of blue cheese being made. When blue cheese is made, the bacteria is often introduced after the curds are ladled into containers to drain and form into a whole wheel of cheese. Today, most cheesemakers use commercially manufactured Penicillium Roqueforti cultures that are freeze-dried. Anyone can order powdered cultures in the mail.

Penicillium Roqueforti

This mold is named after a French town called Roquefort that has caves full of naturally occurring Penicillium mold spores. Cheesemakers in the town of Roquefort created, and still make, the famous blue cheese called Roquefort.

Original recipes for Roquefort cheese required that cheesemakers leave loaves of rye bread in the caves near the town. The loaves became hosts to the ambient mold in the air. After a month or so, the mold inside the loaves of bread was dried, ground, and combined with cheese curd.

The bread simply acted as a host for the ambient mold spores in the cave, as Penicillium Roqueforti is not the same type of mold that grows on any old loaf of bread one might leave out. To further encourage the growth of mold that flavored the cheese, the wheels of cheese were then aged inside the same caves.

The Second Crucial Step in Making Blue Cheese: Needling

After mold cultures are introduced to blue cheese, the “needling” begins. Wheels of cheese are pierced, either by hand or by a device that can poke many tiny holes at once, to create tiny openings. Air enters the wheel of cheese through these tiny holes, feeding the mold, and encouraging the blue/green veins to form.

While the mold cultures and needling contribute largely to the flavor and texture of blue cheese, other factors are always at play. The type of milk that is used (cow, sheep, goat), what the animals were eating before they were milked, and the slightly different cheesemaking techniques used by each cheesemaker ensure that every blue cheese around the world will have its own distinct flavor.

Making Blue Cheese at Home

Blue cheese is not easy to make at home, but if you're interested in trying, the New England Cheesemaking Supply Company provides helpful recipes and cheesemaking kits for such practices.