Blue Cheese – A Comprehensive Guide to Moldy Cheese

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Last updated on March 12, 2023

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Mold. You fight it in your bathroom and in dark corners of the closet. You’ve probably spent years thinking that mold is the enemy. Yet, when it comes to a decadent, creamy blue cheese, the magic can’t happen without mold.  

Mold is the secret behind the famous color of blue cheese as well as its divisive smell and peppery taste. Whether crumbled on a salad or smeared on warm bread with honey, blue cheese elicits passionate opinions from fans and detractors alike. 

To get you as familiar as possible with this distinct cheese, we've broken it down from top to bottom. Leave a note at the below if you have any questions or comments!


Related Article: Gruyere Cheese - A Comprehensive Guide

What is Blue Cheese?

“Blue cheese” refers to a category of velvety, pungent cheeses that all share one feature: they are riddled with veins of green or blue Penicillium mold. These veins snake through the core and soften the cheese’s interior, providing much of its characteristic flavor. Many well-known styles fall into this category, including Stilton, Gorgonzola, Cabrales, and Roquefort.  

How is Blue Cheese Made?

Because there are so many different kinds of blue cheese, it is impossible to describe how each one is made. Like any other cheese, blue cheese involves collecting milk, then forming curds, usually through the combined action of the enzyme rennet and acid-producing bacteria.  

Afterward, the curds are cut, drained, shaped, and aged. What makes blue cheese unique is that early in the ripening phase, the cheesemaker introduces mold spores into the cheese, usually with stainless-steel or copper needles covered in Penicillium spores - a process called “needling."  

In this way, the cheese is also exposed to oxygen (necessary for mold growth) through the needle holes. The mold’s enzymes act on the cheese during aging, softening it and honing its flavor.  

Why is Blue Cheese Blue?

The blue color of this cheese is thanks to Penicillium roqueforti, the mold that crisscrosses the interior of every wheel. It has the lowest oxygen requirement of any of the 200 species in the Penicillium genus, and it secretes enzymes that break down the proteins and fats in milk to produce the silky, spreadable, crumbly delight we recognize as blue cheese.  

The mold’s blue color comes from its spores, or asexual reproductive bodies. They appear blue due to a zinc-containing pigment, which reflects blue light.  

Different Kinds of Blue Cheese

Blue cheeses have some common traits around the world, but the aging time and the type of milk used may differ. These are some of the most recognizable varieties.

Roquefort: Aged 5 months and made from sheep’s milk, this French delicacy is very tangy and sharp. Needling with Penicillium roqueforti occurs after shaping, just before the wheels enter caves to age, usually leaving visible needling lines.    

Stilton: This semi-soft English cheese has a hard rind and becomes crumbly with ripening. Aged 9 months, it is always cylindrically shaped and never pressed. Needling with Penicillium roqueforti after de-molding pierces the wheel to the very center, creating a distinctive radial pattern of needle lines.

Gorgonzola: Made from goat’s milk or unskimmed cow’s milk, Italian Gorgonzola is aged 3-4 months. Needling happens after draining the curds but before the cheese has settled into its final shape, meaning lines are not always visible. The organism used is a sub-species of Penicillium roqueforti called Penicillium glaucum, a slightly milder-tasting strain.  

Cabrales: Not a beginner’s blue cheese, Cabrales is aged 5 months and made from raw cow’s milk. Crumbly with mold pockets that fill with crunchy crystallized tyrosine, this Spanish cheese is not needled or inoculated with mold. Instead, wheels are pressed very loosely, and mold spores autochthonous to the ancient caves where the wheels age find their way into the wheels’ openings. The veins of mold in Cabrales often appear more green than blue, although the mold is Penicillium roqueforti, as in many other blue cheeses.  

Danablu: This mild Danish cheese ages only 10 weeks. Made from full-fat cow’s milk, it has a pliable, edible rind. Needling with Penicillium roqueforti happens during the curd phase, so veins become obscured.  

Blue Cheese Substitutes 

While no other cheese style can substitute for blue cheese, most blue cheeses fill in nicely for one another. If your recipe calls for Gorgonzola, you should feel entirely comfortable using Roquefort or Stilton.

The exception is the double-cream blue cheeses. Because of their very unique texture, they are in a category of their own. You could substitute one double-cream blue for another double-cream blue (for example, switch out Cambozola for Blue Castello), but you should not replace a double-cream blue with a standard blue, or vice versa.  

What Does Blue Cheese Taste Like?

The mold confers to blue cheese a piquant, sharp, and almost peppery note, as well as a smooth, pasty texture. In addition to the mold-derived flavor compounds, blue cheese is also very salty and quite flavorful from the milk, which is usually unpasteurized and quite earthy. Those cheeses made with goat or sheep’s milk may also be bright and tangy.  

Blue Cheese Pairings

Because of its intensely sharp, rich, and salty flavor notes, blue cheeses pair best with a touch of sweetness. Honey, candied nuts, and dried or fresh fruits make exceptionally good companions to blue cheese.  

Best Blue Cheese Brands

When purchasing blue cheese, it makes sense to think of “styles” instead of brands. You will likely need to buy blue cheese in the specialty section of your supermarket; ask for any of the styles listed above. 

However, the tradition of blue cheese has spread beyond Roquefort and Gorgonzola; a few American cheesemakers make phenomenal versions of this spicy fare. In particular, Rogue Creamery of Central Point, Oregon, makes a line of award-winning blue cheeses which hold their own alongside the world’s best.  

Where to Buy Blue Cheese

Some supermarkets sell small packets of blue cheese crumbles in the refrigerated cheese section intended as a salad topping. While these are technically blue cheese, they are a poor shadow of the experience you will have with a bite of Cabrales or Stilton.  

A grocers’ cheese counter or a specialty cheese shop is the best place to purchase blue cheese. If possible, visit a cheesemonger who will offer you samples; try a few before choosing one for your cheese plate!

How Long Does Blue Cheese Last?

Like many soft-ripened cheeses, blue cheese is preserved well under refrigeration. It needs a little exposure to oxygen so the mold can respire. Properly wrapped (in foil or cheese paper--not plastic wrap), blue cheese will last up to a month or even two after you bring it home.

As cheese ages, it changes slightly. Expect the flavor to sharpen and the texture to fragment. This is a natural phenomenon; enjoy watching your cheese mature!

It is a good idea to store blue cheese in a separate container, away from other foods. Mold spores spread easily and may contaminate other items in your refrigerator. While this is not dangerous, mold that is desirable in blue cheese is likely not palatable on cheesecake or leftover shrimp scampi.  

How to Tell if Blue Cheese is Bad?

While blue cheese lasts a long time, it can start to deteriorate with time. The best indicator of spoilage in blue cheese is color--other than blue! If the cheese becomes mottled with patches of pink, brown, orange, yellow, or (worst of all) black, it’s time to let it go.  

If its texture becomes uneven, or if the smell shifts from an earthy bloom to the acrid chemical stench of ammonia, your cheese is no more.  


The deep blue veins of mold in a luscious slice of blue cheese are nothing to be afraid of! Ask your local cheesemonger for a piece of Stilton or Cabrales and put together a cheese plate that will keep your guests talking for weeks.

If you have any questions or comments, don't hesitate to leave a note below.



About the author, Caitlin Clark

Caitlin is a Ph.D student and chocolate researcher at Colorado State University. Her research in the Food Science program focuses on chocolate fermentation (that’s right, it’s a fermented food!) and small-batch post-harvest processing techniques. When she is not acting in her capacity as resident chocolate guru, she researches other fermented foods and beverages like beer, sausage, and natto. Caitlin was drawn to fermented foods while living in rural Spain for six years, where she was exposed to traditional, time-honored practices of food preservation. At home, she practices Bollywood dance for fun and is followed everywhere by two small pet rabbits.