Alternatively, sweets can be especially cooled to prevent crystal formation. Such sweets are called
non-crystalline (or amorphous) and examples include lollipops. Because the sugar molecules are
arranged haphazardly rather than in organised crystals, these sweet breaks easily into small pieces
In a pan, put some sugar and water, and heat. Using a thermometer or a thermocouple, measure the
temperature of the cooking syrup.
When the syrup boils, observe that the temperature increased. Every 5°C above 100°C, pour some of
the syrup on a cold metal surface with oil on it. When this syrup has cooled, observe the consistency
of the product that you get.
III/XII - 2 (of 2)
Syrups sample recovered at temperatures below 127.4°C form transparent, soft solids.
Syrups sample recovered at temperature higher than 127.4°C form transparent crackling solids. They
are “amorphous” solids, where crystallization did not occur, because high viscosity prevented the
sucrose molecules to pile up. However, in these sample, when the water concentration decreases,
crystallization occurs: frequently, you can see that these amorphous solids suddenly because opaque,
because of crystallisation. Pastry makers prevent this crystallization using glucose, whose molecules
go in between the sucrose molecules, preventing them to form crystals.
How to control crystallisation
Preparing sweets with a small number of large crystals e.g. rock candy : Stirring increases the
chances of forming crystals - the more a sugar solution is stirred, the more crystals will form as the
sugar molecules are pushed together, and these crystals will be fairly small, so a few large crystals
Therefore, to prepare rock candy the sugar mixture is not stirred at all during cooling.
Preparing sweets with a large number of small crystals e.g. fudge: When preparing fudge, the aim is to
maximise the formation of crystals, in order to obtain small crystals. To increase the formation of
crystals, a sugar solution should be stirred.
However, if a sugar solution is stirred immediately from the moment it is removed from the heat, a few