Milk is a liquid; cheese is not. Cheesemaking is about solving this problem. To set milk, many of the world’s great cheeses are made using animal rennet—a complex cocktail of enzymes extracted from the first stomach of a calf, lamb, or kid that acts as a coagulant. Some cheesemakers have turned to laboratory-produced vegetarian coagulants in an attempt to save money or appease vegetarian consumers. The best of these mimic the activity of the single-most plentiful component of rennet, the enzyme chymosin.

However, chymosin is not the only enzyme that will coagulate milk; it is possible to set milk with enzymes derived from sources as diverse as fig, papaya, and even black snails. The most distinctive of these alternatives— and also the most widely exploited—is the dried stamen of the cardoon (Cynara cardunculus L.), a relative of the thistle plant native to southern Europe. Cardoon cheeses are in a class by themselves, with a uniquely herbal flavor redolent of dusky flowers. Here, the choice of a vegetarian coagulant is a decision about flavor rather than ideology or boosting the bottom line.

Cardoon Harvest

The use of cardoon stamens in cheesemaking is no modern innovation. indeed, the ancient roman agricultural theorist Columella (AD 4–ca. 70) notes its use in his treatise De re rustica. The thistle rennet cheeses we know and enjoy today all share a common ancestor in simple shepherd’s cheeses made high in the Iberian mountain range now known as the Serra da Estrela. Over subsequent generations, cardoon cheese production spread through southern Portugal and into western Spain, where the technique is still used today.

This family of cheeses is characterized by a relatively quick “make,” meaning the process of transforming the milk in the creamery. The method is similar in many ways to that of the French cheese Reblochon, with very little—if any—addition of lactic acid starter bacteria and with no development of acidity before the addition of the rennet. in this context, it’s significant that these cheeses are all made from raw milk, which allows the milk’s rich biodiversity to shine through in the flavor of the finished cheese.

Cardoon stamens, which are bright purple threads, are harvested in the spring and dried for use throughout the cheesemaking season, which normally extends from October through March. Each day before cheesemaking, the cardoon is prepared in a tealike infusion to yield enzymes. in the past, extraction was encouraged by pounding the stamens in a mortar and pestle; today, a food processor performs the same function. The stamens are steeped in lukewarm (about 85°F) water, which is then strained and added to the milk in the creamery vat. There are innumerable subspecies and variants of thistle, each with its own character; the portuguese regulations specify that producers must make their own infusions from cardoon grown in their respective regions. Each type imparts specific flavors and aromas.

Cardoon has a different mechanism of action from animal rennet. Chymosin works by cleaving the ends off molecules of a milk protein, called kappa-casein, at a specific point, exposing active ends. These bond to one another, creating a strong and flexible network: the curd. The thistle-derived equivalent of chymosin is called cynarase, and in contrast it is a very active and nonspecific protein cutter. The thistle enzyme is particularly appropriate for sheep’s milk. Alyce Birchenough, the cheesemaker and owner of sweet Home Farm in Elberta, Alabama, discovered this the hard way. inspired to experiment with setting the milk from her herd of Guernsey cows with cardoon from her vegetable garden, Birchenough recalls, “I decided on a soft fresh cheese for personal consumption, and the thistle rennet performed exactly as i thought it should. However, after about ten days the cheese developed an unpleasant bitterness.”

Dairy technology consultant Ivan Larcher agrees that cow’s milk poses problems for use with cardoon coagulants. The enthusiastic cutting activity of the cynarase creates five bitter peptides from cow’s milk proteins that are not formed from the proteins in ewe’s milk. serendipitously, the rugged Iberian terrain is ill suited to the needs of delicate dairy cattle, but agile browsers like sheep and goats thrive there.

Under the influence of the cardoon infusion, the milk normally takes around an hour to set. The curd is then cut in successive stages to form particles the size of grains of rice. These are drained and packed into cloth-lined molds of various sizes, and weight is often applied for a few hours to aid drainage in the early stages. Once they come out of their molds, the cheeses can be either brined or dry-salted, and the new cheeses are then stored in cool and humid conditions for approximately 12 days to foster the beginning of rind formation. They finish their maturation in a slightly warmer, drier environment. During this time, a typical practice involves binding the circumference of the cheeses with cloth to provide girdlelike support to their softening bodies. Contrary to their earthy appearance, these are not washed rind cheeses; instead, they are turned and rubbed during this aging process, picking up indigenous yeasts and bacteria.

Reinventing Traditions

Thistle rennet cheeses can be creamy, almost to the point of self-parody. The rampant activity of the cardoon enzyme, coupled with rich sheep’s milk and high moisture, can result in some startlingly unctuous, almost liquid textures. Most producers make cheeses in several sizes, and often one sees them presented with a hole cut in the top, through which the paste can be scooped like ice cream. “This is a pretty recent trend,” says Manuel Maia, of Tradifoods, Portugal’s leading exporter of specialty cheeses. in the case of the Portuguese cheese serpa, a slow Food presidium has been established in direct opposition to the DOP specification, with the express intention of promoting a harder, older version of the cheese that is very different from the softly melting amanteigado (“buttery”) renditions preferred by the local and international market. (professor Harry West, director of the SOAS Food studies Centre at the University of London, ironically notes that the reason the harder cheeses were preferred in the past is that they were used as payment in kind for landless laborers, who naturally preferred that their currency had a longer shelf life!)

Farther north, just outside Bath in Somerset, England, goat cheese maker Mary Holbrook has developed a thistle-coagulated cheese called Cardo inspired by her experiences in Portugal. But hers is a very different interpretation of the category. By letting acidity develop before molding, Mary creates a cheese that breaks down from the outside in, sometimes retaining a chalky core that lends it a gentle acid freshness; she also washes the rind to produce a pink Brevibacterium linens–dominated exterior. Cardo feels timeless (with its hybrid Anglo-Franco-Portuguese technique it resembles some relic of the Napoleonic Wars) but in fact makes no claims to deep historical tradition. Conversely, the slow Food movement has worked in recent years to recreate an Italian thistle rennet cheese inspired by the ancient writings of Columella. Called Caciofiore (literally “flower cheese”), it is essentially a cardoon-set version of Pecorino Romano, made in square molds and matured from one to two months.

Despite their similar recipes, the Iberian cardoon cheeses exhibit profound variation. This is due not only to variation between producers within a group (the DOP and DO specifications are very broad) but also to the season, the size of the cheeses, their provenance, and their age at sale. The vigorous activity of the cynarase enzyme means that some bitter flavors are present in these cheeses. But this is not considered a bad thing. This bitterness counterpoints the cheese’s richness in much the same way that the characteristic quinine flavor of white Châteauneuf-du-Pape offsets the wine’s oily texture and low acidity.

Small-scale experiments aside, cardoon cheese production has not made great headway in the United states. The 60-day rule for aging raw milk cheese cannot be the reason, as it is a regulation shared by the spanish. And Americans would certainly adore their voluptuous textures. given its Mediterranean climate and extensive chaparral, could southern California spawn the next great generation of cardoon rennet cheeses? Torta de Los Angeles, anyone? c

Francis and Bronwen Percival met at the Oxford Symposium on Food and Cookery; he writes on food and cookery, and she is the cheese buyer for Neal’s Yard Dairy. They live in London.