What Is Invert Sugar, and How Is It Made at Home?

Granulated sugar is pure sucrose, a single molecule. When this molecule encounters water, heat, and some acid, it splits into two; glucose and fructose are produced. This breakdown is called inversion, and the resulting mixture is called invert sugar. Two different molecules cannot form an orderly crystal together, so the syrup does not become grainy as it cools. This is also largely why honey resists crystallizing naturally. This breakdown is also carried out with enzymes in industry, but in a home kitchen, the method uses acid and heat.

Making it at home takes patience. Heat sugar and water in a pot; after the sugar has dissolved completely, add a very small amount of lemon juice or citric acid and simmer the mixture over low heat for a long time. Do not stir during simmering; gently swirl the pot if needed. The longer it simmers, the greater the conversion. In home conditions, the exact conversion ratio cannot be measured, so the result is not identical to commercial invert sugar. Choose a heavy-bottomed pot because a thin base can scorch the mixture during a long simmer.

Use only a small amount of acid. Too much acid leaves a sour note in the mixture and spoils the flavor of the syrup. Too little acid slows the conversion, but the syrup can still be used. Wipe away sugar that collects on the side of the pot with a wet pastry brush while simmering. Remove the syrup from the heat before it darkens; if it starts to take on color, it is no longer invert sugar but syrup beginning to caramelize. Do not cover the pot after adding the acid; trapped steam washes sugar from the sides and drips it back into the mixture.

Use it in recipes where its role is clear. Replacing part of the sugar with invert sugar in cakes and cookies keeps them moist longer. In ice cream, it lowers the freezing point, so the mixture does not become rock-hard. In candy making, it prevents crystallization. However, its sweetening power is slightly greater than granulated sugar, and it browns faster in the oven; recipes where the sugars are substituted one-for-one may come out darker on top than expected. It is also used in small amounts in bread dough; it darkens the crust and keeps the inside softer.

Storage is simple. Once cooled, transfer it to a clean, dry jar, seal it tightly, and keep it in a cool cupboard. Because it readily attracts moisture, the lid must close completely; an open jar absorbs moisture from the air and the syrup thins. Do not dip a wet spoon into the jar, because the water and yeast spores it carries can make the syrup turn sour over time. Label the jar, because it looks like honey and can easily be confused with it in the kitchen.