Candy Crystallization

1
Candy Crystallization
Go to Slide Show mode and click the button
2
Heating phase
Unsaturated solution (can dissolve more sugar in
solution)
3
During the heating phase

• The concentration of sugar in the solution is
  increasing due to the evaporation of water
• The boiling point is increasing due to the
  colligative property of boiling point elevation,
  which says that as the concentration increases,
  the boiling point increases

4
Cooling phase
Unsaturated solution
Unsaturated solution
5
During the cooling phase

• There is no change in the sugar concentration
• But there is a decrease in temperature
• At some point (a unique combination of
  concentration and temperature) the solution will
  become saturated (has all the sugar it can
  dissolve at that temperature)

6
Supersaturation

• As the temperature drops below the saturation
  point, the solution becomes supersaturated (has
  more sugar than it should be able to dissolve)
• We can only make candy (i.e., recrystallize the
  sugar) when we are in the supersaturated region

7
Crystal formation

• But when should we induce crystal formation?
• At a relatively high temperature, or
• At a relatively low temperature?
• The answer depends on understanding about sugar
  crystal growth

8
Sugar crystal growth
Sugar
9
Sugar crystal growth
Sugar
10
Sugar crystal growth
Sugar
11
Sugar crystal growth
Sugar
12
Sugar crystal growth

• Sugar crystals grow by having sugar molecules
  deposited on their outer faces
• If we cool the syrup down to just a little above
  room temperature, the crystals will have less
  time to grow before they reach room temperature
  and stop growing

13
Inducing crystallization
Large crystals, coarse
Small crystals, smooth
14
Crystal size and texture

• This is important because in candy (and frozen
  desserts) crystal size texture
• Large crystals coarse, crunchy texture
• No good
• Small crystals smooth, velvety texture
• This is what you want