Cooking sugar is a critical skill in baking, and it’s not hard to do if you just learn a few key food science facts about sugar and crystalization. Watch the video and then answer the questions in the quiz. Then go and cook some sugar!

When we talk about “cooking sugar,” we can mean:

• Reduction: Heating sugar and water and reducing the amount of water in the mixture (this is a “reduction” in the same way you would reduce a sauce)
• Inversion: Chemically changing the sugar by splitting the sugar molecules into different, smaller sugar molecules (typically converting some of the sucrose, which is table sugar, into glucose and fructose, which are simpler sugars than sucrose and which have different properties than sucrose, including sweetness level and how much water they can bind*).
• Caramelization: Radically changing the sugar molecules into completely different molecules that have a different color, aroma, taste, and other properties (caramelization).

* Note: sugar has a very high capacity to bind water. By holding onto water molecules, these water molecules are no longer available to bacteria, which is why sugar can help preserve food. This also causes slower loss of water from the food, which is why cake stays fresher longer than a lean bread like a baguette.

Reduction

When we cook sugar for recipes like Italian meringue (240°F) or toffee (300°F), we are reducing a sugar/water syrup to an exact ratio of sugar to water. It turns out (for reasons that will be explained in the complete course on sugars and starches) that the temperature to which you cook sugar has an exact correspondance with the ratio of water to sugar.

• Thread Stage: 230°–234° F (sugar concentration: 80%)
• Soft-Ball Stage: 235°–244° F (sugar concentration: 85%)
• Firm-Ball Stage: 245°–249° F (sugar concentration: 87%)
• Hard-Ball Stage: 250°–264° F (sugar concentration: 92%)
• Soft-Crack Stage: 265°–299° F (sugar concentration: 95%)
• Hard-Crack Stage: 300°–310° F (sugar concentration: 99%)
• Caramel Stage: above 320°F (sugar concentration: 100%)

Note that the names (such as “soft-ball stage”) are taken from an older practice of taking some of the sugar while it’s cooking and dropping it into a glass of cold water. If the sugar forms a ball that can be squished between your fingers, it’s called “soft-ball stage.” If the sugar forms a ball that you can’t squish, it is “hard-ball stage.” Now, most people use thermometers rather than testing with water.

Inversion

Sucrose (table sugar) is a molecule made up of two smaller, simpler sugar molecules: glucose and fructose. Fructose is much sweeter than sucrose, and glucose is less sweet than sucrose. When we heat sugar in water, some of the sucrose breaks back down into glucose and fructose. If we add an acid (such as lemon juice), this process happens much faster.

It is called inversion (and the resulting sugar is called “invert sugar”) because of the way polarized light bends when it passes through the sugar solution. In the case of invert sugar, the angle of rotation is in a negative direction relative to the angle of rotation with sucrose syrup. This phenomenon is not important for food science, but now you know where the name “invert sugar” comes from.

If you find “invert sugar” on an ingredient list, the manufacturer probably used this type of sugar because of its level of sweetness, its ability to bind water, and/or other properties of invert sugar that are different from sucrose.

Honey is very high in invert sugar and has only a small amount of sucrose.

Caramelization

Caramelization is the process of chemically changing sugar molecules into completely different molecules. This is done because of the intense heat which vibrates the molecules so much they split apart and then recombine to form other molecules.

Note that caramelization only applies to sugar alone. When someone “caramelizes” onions, for example, that is not actually caramelization. It is the Maillard reaction (a complicated chemical process in which sugars and amino acids combine to form new molecules). Other examples of the Maillard reaction are seen in the browning that occurs when you make toast, cook meat, and bake cookies.

If we are caramelizing sugar, we can use water (as we do when we cooking sugar to any of the other stages listed above, which all contain some amount of water), or we can “dry caramelize” the sugar by putting a little sugar, evenly distributed, into a pot and allowing it to melt, then adding another layer and another layer until it starts to break down and caramelize. Some people add all the sugar at once. There are pros and cons to both methods, and it takes a little practice to get the technique down so that all the sugar caramelizes evenly without some burned sugar and some crystallized sugar left. Using the method in this lesson is easier.