sugar concentration in the mixture, the harder and more brittle the sweet will be. If the sugar solution is
removed at approximately 115°C, soft sweets like fudges will form on cooling. If however it is left to
cook until 165°C, a harder sweet like a toffee is formed. At temperatures above 165°C, the sugar
solution will be approximately 99 % sugar. Heating further will cause the sugar molecules to start to
break down and caramelise.
When a sugar solution cools, sucrose molecules slow down and can make pile up regularly, making
crystals. Depending on the way sucrose solution cools the crystals can be very different.
Crystallization occurs always from a seed, which can be impurities, or edges of the vessel containing
the syrup. Sometimes, just one single sugar crystal can cause all of a cooling sugar solution to
crystallise in one crystal, growing considerably. The crystal has then a clearly visible regular shape,
related to the chemical structure of the molecule of sucrose.
If a sugar solution is stirred on cooling, the sucrose molecules will start to bond to each other to from
many crystals. During this process, the crystals cannot grow, and a “paste”, with syrup deprived of
sucrose molecule, containing a lot of tiny crystals. This is called a “fondant”.
Note that, during caramel production, crystallization can be the cause of failure: in particular, as
evaporation of water is faster near the walls of the pan, crystals form there, and they can fall back in
the syrup being cooked. These falling crystals can promote the crystallization of the entire syrup. This
is why pastry chef making syrups generally tap gently the wall of the pan using a brush with water:
crystals are dissolved, so that they cannot promote crystallization.
Sweets containing sugar crystals are called crystalline sweets, and these sorts of sweets can be
further classified according to their crystal size.
Example of a type of sweet containing big crystals is rock candy.
Fudge however, contains many small crystals.