Agitation, stirring or beating supersaturated syrup incorporates air and promotes the formation and growth of sugar crystals due to the rapid movement of the molecules. If the solution is allowed to cool before it is beaten, only tiny crystals forms, which are not allowed to grow. This results in a creamy mass. So when making candy, like fudge, you should allow cooling the sugar syrup to 38°C before beating it, otherwise you will end up with crystals that are too large, resulting in a grainy texture. The beating must also continue until the formation of the tiny crystals is complete, otherwise the excess molecules, the sugar that is still in solution, will migrate to already formed crystals and increase their size. These large crystals will again produce a grainy product.
When making a caramel or candies we want a smooth texture and not a grainy (粒) one. Large sugar crystals will cause a grainy texture in confectionary products. How can we prevent the over-crystallization of the sugar and thereby prevent unwanted grainy textures? Dissolving sugar in a liquid results in a sugar syrup. Most of the time the dissolution of the sugar is promoted by heating the mixture. When the solution starts to boil, water evaporates and the solution becomes more concentrated. Crystals start to form only when the sugar solution reaches a certain concentration. This state is called a supersaturated solution. Now the solution is in a state where not all of the sugar can be solubilised. So the sugar goes out of solution and forms crystals. The saturation point (the maximum concentration of sugar in water without crystal formation) is influenced by the temperature of the solution. It is possible to cool an unsaturated solution to a state of supersaturation. And vice versa, it is possible to heat a supersaturated mixture to an unsaturated solution. Far less sugar can be dissolved in cold water than in warm water, this is also the reason why we heat the mixture to obtain a fast...
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