Thames & Kosmos Candy Chemistry handleiding

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Thames & Kosmos

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Handleiding

Chemical

Reactions

in the

Kitchen

When eggs are heated, they coagulate

(or become solid) because the heat

causes the proteins in the egg to

unfold and then reconﬁgure

themselves with strong bonds

between them.

Because oil and butter

don’t evaporate like

water does when the

temperature increases,

they are added to

baked goods to keep

them moist.

Baking soda and baking powder are used as

leavening agents in baking, to make baked

goods light and ﬂuffy. When baking soda

reacts with acids, it produces carbon dioxide

gas. This gas is what makes cakes and cookies

rise. Baking powder is usually made of baking

soda combined with dry acids so that as soon

as water is added, the reaction begins. Heat

actually speeds up this reaction.

Sugar is added to meringue, whipped

cream, and custard, to make them

ﬁrmer, because the sugar molecules link

to the protein molecules, strengthening

the connections.

In science, it’s important to distinguish

between physical changes and chemical

changes. Simply put, a physical change

doesn’t produce new substances, while a

chemical change does. Breaking an egg is an

example of a physical change, while cooking

an egg is an example of a chemical change.

When you mix ﬂour and baking soda, no

chemical changes occur; but when

you mix baking soda and vinegar,

you get a ﬁzzy chemical reaction.

A special reaction called the Maillard reaction

gives caramel candies their brown color and

unique taste. In this reaction, part of the sugar

molecule reacts with the nitrogen in protein (from

the cream) when they are heated up. This same

reaction gives color and ﬂavor to browned meats,

french fries, crusty breads, and roasted coffee.

When sugar is heated

to 320 °F, it starts to

caramelize, convert-

ing into new sub-

stances and ﬂavor

compounds. When the

sugar gets up to 350

°F, it starts to break

down into pure car-

bon, which is why it

turns black like char-

coal or soot and

tastes burnt.

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