Читать книгу Exploring Kitchen Science - The Exploratorium - Страница 12

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stove—the flame touches a frying pan,

spreading to the oil on the pan and then

to the greens you’re cooking up. There’s

also radiation, which happens in your

oven, where energy is radiated from

the oven’s heating element to your food.

Turn on the gas! When we apply

heat to food, we change its chemistry. In

the case of boiling an egg, for example,

we denature its proteins: The heat

makes the coils of amino acids unwind

and reset in a different form. Heat also

accelerates chemical reactions, which

can transform your everyday ingredients

into tasty treats. When we heat up a

carbohydrate—such as melting sugar for

syrup—it browns and becomes flavorful

in a process called caramelization.

Choose dry or moist. Cooking heat

falls into one of two categories: dry

or moist. Dry-heat methods—baking,

roasting, and grilling—are very hot (at

least 300°F/150°C) and involve no added

moisture, creating a crispier dish with

more flavorful compounds developed

through caramelization and a process

known as the Maillard reaction. Moist-

heat methods—poaching, stewing, and

boiling—use a lower temperature (at or

below 212°F/100°C) and require stock,

steam, or other moisture source. The

lower temperatures allow for longer

cooking times—crucial for slowly

breaking down tough cuts of meat.

A lot goes into transforming distinct foods

into happily harmonized dishes—and each

step and method has science at work.

Get the right ratios. The first task

in any recipe is prepping ingredients. This

can include measuring liquids or solids

(such as cooking oil or sugar) or chopping

veggies or fruits. That’s because your

kitchen is a lab, and, as with any chemistry

experiment, the materials you use will

interact best in certain ratios. Chemical

reactions go more quickly when you chop

food into smaller bits, increasing its

surface area (the amount of exposed tissue)

so it can make more contact with heat and

cook faster. Chop the food into equal-size

bits so they heat at the same rate.

Put it together. Often, the next

step in cooking is to make a mixture

: a

combination of t

wo or more ingredients in

which each keeps its chemical properties.

An example of a mixture is cereal in a bowl

of milk. A solution is a type of mixture

in which one ingredient is distributed

throughout another—much like sugar

dissolved in water. Once the ingredients

are combined into mixtures and solutions,

they progress through the same physical

processes in the next cooking steps.

Pick a type of heat. Usually, we’re

cooking with conduction: transferring heat

to a food through contact. Think of your

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