Post #344822 by The Gnomon on Mon, Nov 19, 2007 8:47 AM

As for caramelization, considerable heat is required. Sugar molecules are made up of various combinations of carbon (C), hydrogen (H), and oxygen (O). As you raise the heat applied to a mass of sugar, you're going send H and O atoms flying off, reattaching whenever possible. When you raise the temperature to a certain point, the H and O atoms are unable to reattach and the C atoms begin to accumulate in large quantities, resulting in the caramelization effect. Taken to the extreme, you could chase off all of the H and O atoms and be left with pure carbon residue suitable for your barbecue grill.

Cane sugar is the disaccharide (double sugar), sucrose, which is made up of two monosaccharides (single sugars), glucose and fructose. Fructose caramelizes at 110º C (230º F) and glucose caramelizes at 160º C (320º F). Fructose is responsible for most of the dark color and flavor changes because because it caramelizes at by far the lowest temperature among the monosaccharides. If you want really dark caramel, use pure honey, which is all fructose.

If you boil sugar water on the stove without a buffer, you can easily get up to the temperature necessary to caramelize fructose; and depending on your particular stove, maybe glucose as well. If you heat your sugar water in a canning jar sitting inside a large pot of boiling water, it is pretty easy to prevent it from reaching 110C/230F. That's because the water inside the jar is being heated mainly by the boiling water outside the jar, which has a temperature limit of 100C/212F. The only additional heat is coming from directly underneath the jar, which bounces around a little in the boiling water (continually cooling that spot toward 100C/212F). So as long as you keep stirring, it would be difficult to caramelize the sugar. If you stop stirring for long enough, the temperature of the sugar at the bottom of the jar could hit 110C/230C.

The Half Boiling Rule of Thumb

In making various kinds of syrups, other than pure sugar, the ingredients other than sugar can undergo transformations to their integrity by overheating. The temperature to overheat many things can be somewhere less than boiling.

I'm not sure who came up with this rule of thumb, but it is older than the hills. Of course, finding the exact temperature that is halfway to boiling is a more modern twist that came about after we could measure temperature.

I use a candy thermometer, which is about a half inch in diameter, about a foot long, and has a clip to fasten to the side of a pot. Using that thermometer, you can fairly easily control the temperature (knowing when to give more heat or less). Just keep the temperature at 50º C or 122º F. It takes more time to make the syrup because the water evaporates a lot slower at the lower temperature.

Anyway, that's what I do when I make my real orgeat, or my passion fruit syrup, pomegranate liqueur, etc. Just as brocolli, cauliflower, cabbage, and other things smell and taste quite different when they are scalded, so do a lot of the things that go into syrups. I try to avoid changing their flavor too much by using the half boiling method.