not cook so well in this cooler oil, so they are usually removed from the fryer, the oil is reheated, and
the chips are then re-plunged in the boiling oil. The crisp outer crust, their golden colour, and the
characteristic taste of chips is due to the coagulation of proteins and rapid water evaporation at the
chips surface, as well as caramelisation of sugars present during frying in the hot oil.
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More about culinary ingredients: Water
Pure water is made of water molecules which are constantly moving around when water is liquid. Each
of these water molecules is composed of two hydrogen atoms and one oxygen atom, organised in a
“V” shape as shown below.
Although this molecule is neutral, and is not charged overall, its electrical charge is actually evenly
distributed throughout its structure – the oxygen (O) atom carries a weak negative charge, whereas
each hydrogen (H) carries a weak positive charge.
This makes the water molecules attract one and other. In water, which contains many of these
molecules, the negative oxygen atom on some water molecules will be attracted to the positive
hydrogen atoms on other water molecules (in a similar way to the north and south poles of magnets)
and this attraction is called a hydrogen bond.
When water is heated, the molecules get more energy and speed, so the water molecules will escape
from the liquid (this is water vapour). At 100 °C, under atmospheric pressure, the energy is such as
water is no longer a liquid and it becomes a gas. In contrast, when water is cooled, the water
molecules will have less and less energy to move around, so bonds between one another are more
important that kinetic energy. The water molecules will be no longer free to move, so the water will
become solid. This is ice.
When water is liquid, water molecules always distribute so that their energy is equal in all
compartments that can communicate.
In particular, when a drop of colored syrup is put in a glass of water, molecular motions will disperse