large crystals will form rather than numerous small crystals (which will make the candy grainy and not
smooth), because the sugar molecules are moving around so quickly that they will readily attach to
already formed crystals and the crystals will quickly grow.
If however, the sugar solution is cooled for a while before it is stirred, more and smaller crystals will be
formed – the sugar molecules move around less quickly so are more likely to bind with a sugar
molecule nearby to form another small crystal than enlarging one that is already formed. Therefore,
when preparing fudge, the sugar solution should be allowed to cool undisturbed to approximately
43°C, and then stirred vigorously to maximise the formation of lots of small crystals that make the
Preventing any crystals forming e.g. lollypops: When preparing for example lollypops, the aim is to
prevent the sucrose molecules from forming crystals at all. This can be achieved by cooling a sugar
solution so quickly that that the sugar molecules stop moving even before any crystals have had time
to form. The sugar molecules will just settle where they are in a disorganised mess. The sugar mixture
should not be stirred on cooling, since stirring initiates crystals formation. Crystal formation can be
a) adding an interfering agent – adding lots of other non-sucrose sugar molecules to the original sugar
solution will prevent sucrose association and thus...
solution will prevent sucrose association and thus crystal formation. This can either be done directly,
by adding a different sugar eg corn sugar, which contains long chains of glucose molecules that tend
to prevent the sucrose molecules from crystallising; or by adding a fat source (eg butter for toffee).
b) alternatively, the sucrose can be inverted by adding acid – this will cause the sucrose to break up
into glucose and fructose, reducing the sucrose concentration, and thus sucrose association and
crystal formation. This is another reason why the solution should not be stirred on cooling - stirring or
agitation is one of the factors that may encourage the hydrolysed fructose and glucose molecules in