What Einstein Kept Under His Hat: Secrets of Science in the Kitchen (10 page)

Several different
Penicillium
species are used in making cheese, either by injecting the mold culture into the cheese (interior-ripened cheese) or by coating the cheese rounds with the mold (surface-ripened cheese). The molds contribute good flavors and impart a soft “bloom” to the cheese surfaces. Among the species most commonly used are
P. camemberti
for Camembert;
P. glaucum
for Gorgonzola;
P. candidum
for Brie, Coulommiers, and several French goat cheeses, and
P. roqueforti
for Roquefort, Danish blue, and Stilton.

The bacteria.
Bacteria, of course, can also be good guys or bad guys. Among the common black-hat, pathogenic bacteria are
Listeria monocytogenes
and certain members of the genus
Brucella
. The symptoms of infection by these bacteria are called listeriosis and brucellosis, respectively. Brucellosis goes by several different names—Malta fever, Mediterranean fever, Cyprus fever, etc.—depending on the part of the world in which the various
Brucella
species have caused the most trouble. (The name undulant fever comes from the fact that the fever chart of a brucellosis sufferer undulates up and down as the days go by.)

Both the
Listeria
and the
Brucella
bacteria, along with other pathogenic villains such as
Campylobacter jejuni
, several species of
Salmonella
, and the ever-popular
Escherichia coli
O157:H7
can breed in the moist environments of dairies and cheese plants.

The cheese.
For more than fifty-five years, the FDA has required that all cheeses sold in the United States, whether domestic or imported, meet any one of the following three conditions: (1) the milk it is made from has been pasteurized by being heated to 145ºF (63ºC) for 30 minutes or 161ºF (72ºC) for 15 seconds, (2) the cheese itself has been subjected to equivalent heating conditions, or (3) the cheese has been aged for at least sixty days at a temperature no lower than 35ºF (1.7ºC). Long aging to produce the harder cheeses such as Gruyere and Cheddar both increases the acidity of the curd and dries it out, and many bacteria cannot multiply under dry, acidic conditions. But soft cheeses, which are not aged as long, cannot be made with absolute safety from unpasteurized milk.

Over the past several years, the FDA has been making noises about lengthening or eliminating the sixty-day aging option, that is, forbidding the distribution of any cheese, aged or not, that was made from unpasteurized or “raw” milk, on the grounds that
Listeria
and
E. coli
bacteria have been known to survive a sixty-day aging period. (The second option, pasteurizing the finished cheese, is in most cases quite impractical.)

Vociferous objections to this trial balloon have been raised in many quarters, including European cheese makers and exporters, who use raw milk for many of the products they’re most proud of; American artisanal cheese makers; and just plain food lovers, many of whom believe that pasteurization damages flavor and that illness from
Listeria
contamination of cheese is very rare, anyway. (Of the few hundred annual listeriosis deaths in the United States, it is difficult to pin down how many may have been caused by cheese, because other foods, notably hot dogs, delicatessen meats, and chicken, are the major sources of
Listeria
contamination and many outbreaks have no identifiable source.)

So, can we still buy cheeses made from unpasteurized milk? Yes. As of this writing, they’re sold quite legally in many markets. The labels will say they’re made from “raw milk.” Do some producers cheat by aging their raw-milk cheeses for less than sixty days? Indubitably. Will the FDA ever ban all unpasteurized cheese? If they do, it will be over the figurative dead bodies of thousands of cheese lovers.

Tune in tomorrow for the next episode of “As the Cheese Wheel Turns.”

What gives string cheese its peculiar texture? It pulls apart in strands.

....

S
tring cheese is a novelty form of mozzarella, a soft, white, elastic cheese.

American mozzarella, made from cow’s milk, is a poor relation to the Italian mozzarella (
mozzarella di bufala
) from the region along the shinbone of the Italian boot.
Mozzarella di bufala
is made from milk of the Asian water buffalo, introduced into Italy in the seventh century—a totally different animal from the American plains “buffalo,” which isn’t a buffalo at all, but a bison. Italian
mozzarella di bufala
is infinitely more moist, creamy, and delicately flavored than the cow’s-milk product whose native habitat in the United States is on top of a pizza.

In making mozzarella, the milk is coagulated and separated into Little Miss Muffett’s proverbial curds (the protein and fat) and whey (the remaining watery liquid). The curds are then mixed with some hot whey and stretched and kneaded until the mixture becomes smooth and rubbery.

To make string cheese, the curd is melted and heated to 170°F (75°C), then pulled and stretched like taffy, but mainly in a single direction, so that the milk protein (casein) molecules line up and give the cheese a directional structure. The cheese is sold in the form of cigar-shaped rods that can be peeled like a banana into long, fibrous strands that look like, well, string.

Why on earth string cheese exists, I don’t know, except that kids like to play with it. And it can be consumed as a hand-held snack, like a vegetarian Slim Jim.

I see many kinds of “process cheese” convenience foods in the supermarket. How are they related to traditional cheeses like Cheddar, Swiss, and so on? Do they all contain “real” cheese, and if so, how much?

....

I
n addition to the hundreds of classic cheeses developed over more than a thousand years in various parts of the world, we are blessed (?) today with many options for adding cheese flavor, be it natural or artificial, to our snacks and dishes. Dozens of cheesy (often in more ways than one) factory-produced concoctions beckon to us from the market’s refrigerated cases. Almost all of them contain “real” cheese, but their ties to reality can be rather thin.

The primary virtue of these so-called “process” (not “processed”) cheeses is that unlike many classic cheeses they are easily meltable and blendable. That’s because they often contain emulsifying agents and/or have been beaten into smooth submission long before they reach your kitchen.

Classifying them, as you can imagine, can be quite a chore, but the FDA is up to it. Here are the FDA-defined categories in order of diminishing faithfulness to the historic and revered concept of cheese.

• 
Pasteurized process cheese:
A mixture of two or more cheese varieties that have been heated and blended together with an emulsifier and optional ingredients such as water, salt, or coloring, into what the FDA appetizingly calls “a homogeneous plastic mass” with a minimum of 47 percent milk fat. These cheese products may contain added cream or fat, making them more easily meltable, but they must be at least 51 percent actual cheese. Example: Most American cheeses.

•
 
Pasteurized process cheese food (note: not a “cheese” but a “food”):
A pasteurized process cheese containing enough added ingredients such as cream, milk, skim milk, buttermilk, or whey to reduce the percentage of actual cheese in the product to below 51. May contain emulsifiers such as phosphates, citrates, or tartrates, but must contain at least 23 percent milk fat. Example: Land O’Lakes American Singles.

•
 
Pasteurized process cheese spread:
A pasteurized process cheese food that may contain a sweetener plus stabilizing and thickening gums such as xanthin or carrageenan. Must contain at least 20 percent milk fat. Example: Kraft Olive and Pimento Spread.

•
 
Pasteurized process cheese product:
Any process cheese product that contains less than 20 percent milk fat. Examples: Kraft Singles, Velveeta.

•
 
Imitation cheese:
Made from vegetable oil. Minimum milk fat: zero percent. In a glass by itself is Cheez Whiz Cheese Dip or Cheese Sauce. After whey, its most abundant ingredient is canola oil. Milk fat? Less than two percent.

•
 
Orange glop:
Not an official FDA classification, but the name I give to the stuff they pour over nachos, French fries, and hot dogs in places I wouldn’t eat in.

. . . And consumers are supposed to think they’re all simply “cheese”?

When I make a sauce by deglazing the pan with wine or stock after sautéing meat, the result is usually too thin for my taste, even after I reduce it. So in accordance with French culinary custom, I “finish” the sauce by adding a “nut” of butter and whisking it in lightly, whereupon the sauce magically thickens. Adding any other fat, such as olive oil, doesn’t do that. Why does butter do it?

....

C
alling butter a fat is like calling a truffle a mushroom. Butter’s magic arises from its uniqueness, not only in its history and renowned flavor but in its composition. Butter contains a relatively large amount of water, and it’s the water that gives butter its unfatlike properties, such as being able to bring a sauce together and frothing up when heated in a sauté pan. I’ll get to these two phenomena later, but first, a little background.

Butter is a complex blend of fat (by law, at least 80 percent in the United States and 82 percent in the European Union) and water (16 to 18 percent), plus 1 or 2 percent protein (mostly casein) and, if salted, 1.5 to 3 percent salt, which both kicks up the flavor and wards off rancidity. A touch of a fat-soluble yellow-orange pigment is often added, especially in the winter, when cows of most breeds produce paler fat because their diets are devoid of carotene-rich, new-growth vegetation. The pigment, used also to color cheese, is annatto (
achiote
in Spanish), from the seeds of the South American tree
Bixa orellana
.

Fats and water won’t ordinarily mix. But in butter, the milk’s fatty part (the butterfat) and watery part (the buttermilk) are combined in what appears to be a homogeneous mass. On a microscopic scale, we would see that the water is in the form of tiny globules (measuring less than 0.0002 inch), dispersed uniformly throughout the sea of semi-liquid fat like so many poppy seeds in a Jell-O mold. Such a stable configuration of two liquids that won’t ordinarily mix is called an emulsion. (See p. 378.) Butter is a water-in-oil emulsion.

Seemingly paradoxical is the fact that butter is made from cream, an emulsion with precisely the opposite structure. Cream consists of microscopic fat globules dispersed throughout a watery liquid: an oil-in-water emulsion. When cream is churned into butter, the mechanical action breaks open the surfaces of the tiny fat globules so that they can coalesce—first into rice-sized grains, and ultimately, after being squeezed and kneaded, into a continuous mass incorporating microscopic globules of water.

But, you say, butter is mostly solid fat, not a liquid oil. Actually, it is both. For one thing, in chemistry, the same word,
fat
, is used whether the substance happens to be solid or liquid at room temperature. Moreover, the milk fat in butter is partially in the form of a sea of soft, almost liquid “free fat” and partially in the form of solid crystals. Butters that have been churned at different temperatures and then cooled and tempered differently (much as a pastry chef tempers chocolate to control its fat crystals; see p. 435) wind up with different ratios of free fat to crystals, and hence with different degrees of firmness, ranging from soft spreaders to bread shredders.

Enter the wee little beasties. Several breeds of bacteria, some good for us and some bad, view milk sugar (lactose) as yummy victuals and will thrive in cream if we let them. The bad ones can be knocked off by pasteurization, while the good ones can be encouraged by warm temperatures to go ahead and nosh, generating some wonderfully flavorful by-products as they do. Both of these measures have important consequences for the butter.

In the United States, all cream used to make commercial butter must first be pasteurized by being held at 165°F (74°C) for 30 minutes, a process that connoisseurs insist imparts a slightly cooked, off flavor compared with down-on-the-farm, unpasteurized butter. In the best of all possible worlds, though regrettably not very often in our part of the world, the cream will then be cultured (or “ripened,” “matured,” or “soured”) by the addition of bacteria, usually a mixture of
Lactococcus
and
Leuconostoc
strains, which produce lactic acid and diacetyl. Lactic acid adds a pleasant tang to butter, while diacetyl is the chemical that gives butter its most prominent characteristic flavor. Unfortunately, most American mass producers of butter (at up to 8,000 pounds per batch) skip the time-consuming culturing step.

By this time you have figured out that butter froths up in the sauté pan because its water turns to steam, which then bubbles its way out noisily. But in spite of its high water content, hot butter doesn’t spatter in the pan as other hot fats do in the presence of water. Instead, the butter merely foams up around the food. That’s because butter’s water is in the form of individual, microscopic globules. They don’t join together into droplets that, in contact with hot fat, would explode into relatively large bursts of steam, carrying spatters of hot fat along with them.