Marlene Parrish - What Einstein Told His Cook 2

THE FOODIE’S FICTIONARY:Peptide—a strong riptide

Sidebar Science: Micelles, not your cells

IN THE CONVERSIONof milk into yogurt, the bacteria-produced acids act on the milk’s protein, which is mostly casein, to make its tiny, widely dispersed globules (its micelles ) come together into a solid mass. This happens when the bacteria have acted long enough to produce a certain level of acidity. For casein, that’s a pH of 4.6, its so-called isoelectric point , at which the micelles (pronounced MY-cells) lose their mutually repulsive electric charges and can stick together. What one observes when that acidity level is reached is that the milk coagulates, or curdles into curds and whey. Down at the yogurt works, they then homogenize the curds, whey, and milk fat into a single, smooth texture.

Yogurt Cheese

If you like yogurt but prefer a thicker consistency, you can make cheese out of it by draining off the whey. Yogurt cheese can stand in for semisoft cheeses. It makes a good spread for bagels or bruschetta and takes to the added flavors of herbs. Serve it sweetened with honey as a dessert cheese with crackers.

2 cups plain whole-milk or low-fat (not nonfat) yogurt

1.Empty the yogurt into a fine-mesh strainer or into a colander lined with several layers of cheesecloth. Place the strainer or colander over a bowl.

2.Put the setup in the refrigerator and allow the yogurt to drip and drain for 2 to 24 hours. The longer the yogurt drains, the denser it will be. The liquid that accumulates is the whey. It may be discarded.

3.The semisoft yogurt cheese in the strainer or colander will be thick enough to spread, and the consistency will be somewhere between sour cream and fresh goat cheese.

MAKES 2 CUPS

DIY Sour Cream

You can make Do-It-Yourself sour cream using the “good bugs” in buttermilk: Streptococcus lactis , S. cremoris , and/or S. diacetylactis , with some Leuconostoc thrown in for good measure (and flavor). They’ll feed on the cream’s lactose, producing pleasantly sour lactic acid. While buttermilk is made from skim or partially skimmed milk, turning these bacteria loose on high-fat cream will produce a much richer product.

Unlike commercial sour cream, the homemade kind—provided you’ve made it with heavy cream—can be whipped. When whipping it, be careful not to overwhip, because it can turn suddenly to butter. Homemade sour cream, whipped or plain, makes a delicious topping for fruit tarts and for many chocolate desserts.

Old-fashioned pasteurized cream will thicken in 24 hours and will have a delicious tang. Ultrapasteurized cream will take a little longer to thicken and will have a softer texture. Both can be kept in the refrigerator for a whole month; the sour cream will get thicker and more flavorful.

2 cups heavy cream

5 teaspoons buttermilk

1.Combine the cream and buttermilk in a screw-top glass jar. Shake the jar for 1 minute.

2.Let the jar stand at room temperature for 24 hours while the liquid thickens to the consistency of sour cream. If the room is especially cool, you may need to let it stand an additional 12 to 24 hours.

3.Refrigerate for at least 24 hours, or preferably longer for better flavor and consistency, before using.

MAKES 2 CUPS

HOW SOFT IS SOFT-SERVE?

I brought home a quart of Dairy Queen soft-serve ice cream and put it in my freezer. To my surprise, the next day it was just as hard as any ordinary ice cream. I thought the soft serves, like Dairy Queen and frozen yogurt, were special formulas that always had that lovely, voluptuous mouth feel that I like so much. What happened?

A(chocolate) Dairy Queen aficionado myself, I tried your experiment twice. Each time, as soon as I got the quart container into the car I measured its temperature by plunging a so-called instant-read thermometer into the middle and waiting for a couple of dozen “instants” until it reached its final reading. On the two occasions it measured 14 and 16°F (—10 and—9°C). Then, after a couple of days in my freezer, somewhat diminished in quantity by after-dinner “scientific tests,” each quart measured 0°F (—18°C). My soft-serve, like yours, had become just as hard as ice cream.

Thus, Dairy Queen and the other soft-serves are nothing but ice cream at a warmer temperature. We love them not only because of their softer, smoother textures but because our palates are more sensitive to flavors at warmer temperatures.

The American Dairy Queen Corp. lists the ingredients of its vanilla product as milk fat and nonfat milk, sugar, corn syrup, whey, mono-and diglycerides, artificial flavor, guar gum, polysorbate-80, carrageenan (the last three are thickeners), and Vitamin A palmitate. Milk fat, the main ingredient, is of course butterfat, and butter is harder at lower temperatures because more of its fat is crystallized. (See chapter 2.) The mono-and diglycerides behave similarly to the butterfat’s whole fats ( triglycerides ), while the guar gum and carrageenan thickeners also tend to tighten up at lower temperatures. So it’s no wonder that the Dairy Queen is soft when you buy it but hardens in the freezer.

At Dairy Queen, TCBY, Carvel, and many other franchised and independent stores, rivers of various soft ice cream products, including nonfat ice cream, low-fat ice milk (which perversely contains less milk than ice cream), frozen yogurt, and frozen custard, flow like lava from smug-looking machines that guzzle batches of packaged mixtures dumped into their maws. The machines mix and chill them, adjust their temperature and viscosity, and dispense them in a variety of flavors, even swirling two flavors together for irresolute customers who can’t decide between chocolate and vanilla. (Can there be any question?)

Dairy Queen’s product is a reduced-fat ice cream containing 5 percent fat. TCBY sells both nonfat and 4-percent-fat (billed as “96 percent fat-free”) frozen yogurt. Frozen custard is the smoothest and creamiest of all, and as a consequence the fattiest. (There’s no free lunch.) Typically it contains 10 percent butterfat and a minimum of 1.4 percent egg yolk solids.

Moving up the fat ladder, we come to “ordinary ice cream.” Federal regulations require that ice creams without solid additives such as nuts or candy bits contain at least 10 percent butterfat. The leading fake-Swedish-named brand contains 16 percent butterfat.

THE FOODIE’S FICTIONARY:Custard—the last stand in a food court

COOL, MAN!

Does eating ice cream in hot weather cool you off?

People do seem to think so. At my local Dairy Queen there is always a long line of people seeking cool after-dinner desserts in the summer, but starting the day after Labor Day, the place is virtually “desserted.”

The answer to your question is in fact, no. After all, we are warm-blooded creatures with thermostats set at 98.6°F (37°C), and eating something cold cannot change that. Our cooling mechanism is purely a surface phenomenon: the evaporation of perspiration from our skins, assisted, when we’re lucky, by a breeze that hastens the process. Putting ice cream into one’s mouth serves only to cool the mouth. You’d do much better by smearing the ice cream all over your body.

According to my calculations, melting a one-inch, 0°F (—18°C) ice cube in the mouth would absorb only 1.3 calories of heat. If distributed over the entire body, that amount of heat loss would lower the temperature of a 150-pound person by 0.007°F (0.004°C).