Learn about the unsung hero of cheese.

What are cheese cultures? They’re the unsung heroes of the cheesemaking process. A starter culture is “friendly” bacteria with a job to do— to start the transformation of milk into cheese. These cultures are used in the making of the vast majority of cheese (and in yogurt, too); they help turn milk’s natural lactose sugar into lactic acid. This acidifying process makes the milk curdle and separate into curds and whey. Curds are the foundational ingredient in cheese. Starter cultures also work to develop the flavor and body of the cheese during the cheesemaking and afterwards, as the cheese ages.

“It’s the closest thing you can get to magic in everyday life, watching liquid milk to curds and whey,” says Tom Perry, cheese sales manager at Shelburne Farms, based in Shelburne, VT. Perry received the Daphne Zepos Teaching Award, which allowed him to travel to Europe to learn about native bacterial cultures used in cheesemaking. As a former cheesemonger, he “wanted to understand how these different cultures impacted the destiny of the cheeses I loved selling.”

It turns out they impact the destiny enormously. “Cheese cultures ultimately drive what cheese it’s going to be, from flavor to texture,” explains Brian Civitello, founder and cheesemaker at Mystic Cheese, in Groton, CT, although “cultures alone do not make a cheese.” A cheese’s ultimate character comes from a variety of factors, from the quality of the milk to the cheese-making process and equipment to the maturation of the final product. Cultures, though, are a fundamental and deeply influential part of the process, a “crucial piece of the puzzle,” according to Civitello. They are integral to giving each cheese its distinctive personality.

Isolating What Was a Mystery

Cheese, which has been made for thousands of years, consists of four fundamental ingredients: milk, salt, rennet and cultures. Before the arrival of germ theory in the 1850s, the science behind cheesemaking was poorly understood. Cultures are naturally-occurring in milk, and over countless generations, microbes evolved and adapted. Without refrigeration and other modern technology, milk left on its own soured and curdled.

As sanitation and health knowledge deepened, cheesemaking changed. Producers began to pasteurize milk in order to kill off potentially pathogenic microbes. But because the “friendly” bacteria would also get annihilated during pasteurization, they needed to add back starter cultures to aid in making cheese. These cultures were isolated and, over time, refined and refined again. Hence, the birth of modern cheesemaking and commercially-derived cultures, which are now a pretty standard part of manufacturing cheese.

“Hundreds of years ago, they really had no idea what was going on,” says Civitello. “Now you can see the general makeup of the bacteria in a microscope and know pretty much exactly what is happening.”

With advancing scientific knowledge, technicians became adept at selecting and breeding certain strains, creating blends of bacteria designed to help create specific flavors. If you are a cheesemaker looking to make a Gouda-style cheese, for example, you will know precisely which blend of cultures to choose in order to foster the nutty, sweet, caramelized flavor that shines in that cheese. If you’re making brie-inspired cheese, you’ll choose a different set to create its characteristic buttery creaminess.

There is a handful of cheesemakers in Europe who embrace the old, wild way of making cheese, with raw milk and no added started cultures. Or, they make their own starter—a mother culture—from soured or clabbered milk, harnessing native microbes through milk cultures. (Civitello likens this to “blindly throwing the bowling ball down the lane.”)

These natural cheesemakers are the exception. Almost all cheesemakers, whether they use raw or pasteurized milk, work with added cultures. “It’s sort of a handshake that goes on,” Civitello explains. “You work with the bugs, and the bugs work with you.”

Harnessing Bacteria

Robert Aguilera, an account manager at Milwaukee, WI’s Chr. Hansen, a bioscience company that develops and manufactures ingredients, including cultures, encourages us to think about cultures as part of the “dynamics of place.” Just as climate and soil are part of terroir, the sense of place, so is microbial life. Look at Comté, a cheese crafted in the foothills of the French alps since the Middle Ages, and its cousins: Gruyére, Raclette and Appenzeller.

“These cultures developed around the Alps, and the similarity among cheeses in regions existed because of similar microbial life,” Aguilera says. At Fort Saint Antoine, in the French Haut Doubs forests, thousands of wheels of Comté age, just as thousands and thousands have sat maturing before them. “The microbial life has existed there for a long time,” Aguilera notes, “All those cheeses foster microbial communities, growing and igniting” to give each wheel of Comté its unique personality.

Bacteria are everywhere, from the grass the cows eat to the milk they produce to the surface of our skin. “Bacteria are natural, we’re harnessing them and using them to our advantage,” explains Dave Potter, owner of The Dairy Connection, a Madison, WI-based culture distribution company. He describes cultures as “the living organisms that are added to milk to produce flavor…When the bacteria start to die off, the enzymes start to break down protein, fat and sugar to create flavor in aged cheeses.”

In addition to the starter cultures, adjunct cultures may be added to deliver enzymes and create a specific flavor profile, perhaps playing up sweet or roasted flavors. Some bacteria are helpful in creating crystals as the cheese ages and protein chains unravel to create small, crunchy deposits.

Potter’s company, as well as other culture companies, “isolate bacterial strains to work the same every time you make a batch,” says Potter. “Over the past 30, 40, even 50 years, cultures have been more and more refined.” These cultures usually come in freeze-dried packets (for small cheesemakers) or big barrels for industrial producers. Either way, there would be no cheese without them.

Classifying Cheese Cultures

Cheese cultures are often grouped by the temperature range at which they work. Mesophilic bacteria grow best at lower temperatures (a mesophilic culture will propagate best at temperatures up to 90 degrees F), and thermophilic bacteria thrive in higher heat (above 90 degrees F). Mesophilic culture blends are used primarily for American-style and specialty cheeses, like brie and cheddar. Italian-style cheeses like Parmesan often call for thermophilic cultures.

Mesophilic bacteria can be further divided into two categories: lactic acid starter bacteria, like Lactococcus lactis subsp. lactis and Lactococcus lactis subsp. Cremoris, are primarily used for producing lactic acid, and aroma-producing bacteria, which create carbon dioxide gas and flavor. These include Lactococcus lactis subsp. lactis biovar diacetylactis and Leuconostoc mesenteriodes subsp. Cremoris. Many culture blends contain a mixture of these two types of mesophilic bacteria.

Surface-ripened cheese, cheeses that ripen from their rinds (their outside surface) inward to the interior paste, call for their own recipe of cultures. Brevibacterium linens (aka B. linens) are encouraged to grow on washed rinds cheeses like Taleggio and Epoisses. Bloomy rind cheeses, like brie and Camembert, are made by adding Penicillium candidum (or a blend of P. candidum and other molds) to the milk. Another category of cheeses has wrinkly, “brain-like” off-white rinds made from Geotrichum candidum on the ripening surface (think La Tur, Saint Marcellin and crottin).

Blue cheeses are inoculated with Penicillium roqueforti, which originated in the caves at Roquefort in France, or Penicillium glaucum (found in Bleu d’Auvergne and Gorgonzola Dolce), to give them their blue-green veining. Fun fact: only one teaspoon of blue mold is required to inoculate a 1,500-gallon vat of milk.

The Magic (and Loss) of Biodiversity

As cultures have been refined and manufactured over the years, it has meant change for the world of cheese. A relatively small number of biotech companies produce the freeze-dried microbes, and there have been consolidations among the companies that propagate and bank cheese cultures. (In turn, cheesemaking has evolved away from small scale creameries in favor of large-scale operations focused on more commercial cheeses.) Some argue that both of these trends impede biodiversity.

Some small cheesemakers have decided to use farmhouse cultures, which “were isolated from farms back when starters first became an added ingredient and sometimes contain a more diverse mix of microbes than commercial starters,” Perry explains. “Other cheesemakers are using methods that harken further back, harnessing their very own populations of bacteria.” This is an involved and labor-intensive process, and cheesemakers must have stringent food safety measures in place to ensure they are fostering a healthy, safe microbial environment. Creating any sort of consistency with this method is an enormous challenge.

Most turn to commercially-available cultures. The science behind these is constantly advancing and impressive. The companies that design and manufacture cultures have new ways to prevent bacteriophage, a virus that kills off starter cultures, rendering them ineffective and ruining entire vats of milk. Starter cultures are also faster than ever before, which reduces the time it takes to make cheese, and also, therefore, the cost of production. They’ve created cultures that increase productivity and ensure a more consistent final product.

For Civitello, “sculpting how I want my cheese to taste and figuring out which will make the best cheese” is a creative process. There are a lot of questions that go into choosing the perfect blend of cultures: “Will it produce gas formation in the cheese? Will it create the best flavor for fresh cheeses or for ripening long term? Will it continue to produce flavor?” The culture is only as good as the milk, the cheesemaker, the recipe…even the packaging and the storage. “The cheesemaker is the director of the orchestra,” says Potter. “Cheese culture is one of the instruments. The cheese becomes the symphony.”

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