Lesson 7 - Confectionery Applications

Crystalline vs. Non-crystalline Confections

To some, confectionery development remains more of an art than a science, yet no one can dispute the significant role that sugar crystallization plays in forming a confection's texture and contributing to its mouthfeel. In fact, the wide variety of candies exist today because of the ways in which sugar can be manipulated in its crystalline form.

 

Sugar Crystallization


Sugar crystals melt during a heating process and recrystallize when the supersaturated solution is subsequently cooled. The type of crystals that form during cooling depend upon boiling and cooling temperatures, agitation, the presence of other ingredients such as stabilizers and fats, and the pH of the solution.

 
rock candy
  fondant

Very large, coarse crystals develop when a supersaturated sucrose solution is cooled without agitation, which forms the basis of rock candy.

A sugar solution that is rapidly cooled with agitation produces very fine crystals that are used in cream-filled centers or fondant.

 

Sugar crystals range in size from very fine to very coarse. Non-crystalline sugar solutions can harden into an amorphous state, referred to as a glass. For many confections, it is critical that sugar remain non-crystalline. In these candies, crystal formation, or graining, can result in cloudiness or loss of smoothness. The following chart highlights those candies that are categorized as crystalline and those that are non-crystalline.

 
Crystalline Candies Non-Crystalline Candies
Chocolates Hard candies
Fudge Toffee
Fondant Caramel
Nougat Gummed candies
Tablets  
Panned candies  
Marshmallows  
 

Controlling Crystallization

As previously mentioned, factors affecting sugar crystallization include temperature, agitation, viscosity, sweetener type and the presence of other ingredients in the formulation. It is more difficult for sugar to recrystallize and grow in formulations that are more viscous. Higher-DE corn syrups decrease the viscosity of a solution, while lower-DE syrups increase it.


Fructose is typically more soluble than sucrose and thus tends to stay in its non-crystalline phase, or syrup phase. Since honey is composed primarily of fructose and glucose, it is often used to retard sucrose crystallization in candies, as are corn syrups.

 
candy making
 

Exercise 1

What do you suppose might happen when a supersaturated sugar solution is boiled, but not all crystals have dissolved or melted?

If not all crystals are allowed to dissolve and melt, they act as nuclei or seeding sites for the formation and growth of new crystals. This is undesirable in the manufacture of hard candy, an amorphous glass-like product, where sugar recrystallization can produce a grainy mouthfeel and/or cloudy appearance.


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