Concentrated Sugar Syrups and Caramel

In some cases, as when making a sugar syrup for Italian meringue, the sugar is concentrated to produce a supersaturated solution, which contains the maximum amount of sugar possible at room temperature without its precipitating out into crystals. This is accomplished by heating the solution, which enables the water to dissolve more sugar than it could at room temperature (cold water is capable of holding double its weight in sugar).

A supersaturated sugar solution begins with sugar partially dissolved in at least one-third its weight of cold water. It is stirred continuously until boiling, at which time all the sugar will dissolve. If sugar crystals remain on the sides of the pan, wash down the sides with a wet pastry brush. Once the sugar is dissolved, the solution is considered supersaturated and, to avoid crystallization, must not be stirred. As the water evaporates, the density of the solution increases and the temperature rises. As long as there is a lot of water in the syrup, the temperature does not rise much above the boiling point of the water. But once most of the water has boiled away, the temperature can then rise dramatically, passing through various stages and eventually rising to the temperature of pure melted sugar (320°F/160°C) when all the water is gone. Once the sugar has liquefied and all moisture is removed, the sugar then begins to caramelize, and its sweetening power decreases.