Invert Sugar
Invert sugar is a syrup of glucose and fructose made by splitting sucrose, ordinary table sugar, into its two building blocks. Bakers, candy makers, and ice-cream makers use it because it keeps products moist, soft, and smooth.
The chemistry
Sucrose is one glucose molecule bonded to one fructose molecule. Adding water across that bond, a reaction called hydrolysis, breaks it apart. Heat plus acid speeds the reaction up, and so does the enzyme invertase, which bees and yeast both use.
The name comes from polarized light. A sucrose solution rotates light one way; once inverted, the mixture rotates it the other way. Chemists noticed the flip first and the name stuck.
Why it behaves differently
It resists crystallization. A syrup with three kinds of sugar molecule cannot easily stack into neat sucrose crystals. That is why a squeeze of lemon in caramel helps, and why fondant and ganache stay silky.
It holds water. Fructose is strongly hygroscopic, so cakes and cookies made with invert sugar stay soft longer and stale more slowly.
It lowers the freezing point more. Two small molecules dissolved in water depress freezing roughly twice as much as one sucrose molecule. Ice cream with some invert sugar scoops softer straight from the freezer.
It browns faster. Glucose and fructose are reducing sugars, so they join the Maillard reaction readily. Expect darker crusts at the same oven temperature.
It is sweeter. About 1.2–1.3 times as sweet as sucrose by weight.
Making it at home
| Ingredient | Amount |
|---|---|
| Granulated sugar | 500 g (about 2 1/2 cups) |
| Water | 250 ml (1 cup) |
| Cream of tartar or citric acid | 1/4 tsp or 1 g |
Bring to a simmer, wash down the sides, and cook without stirring to about 114 °C / 236 °F, which takes 20–30 minutes. Cool to room temperature. It should be pale gold and thick. Store sealed at room temperature for up to 6 months.
Using it
Replace 10–25% of the sugar in a recipe with invert syrup, by weight. More than that can make baked goods gummy and overly brown. Good targets: chewy cookies, ice cream and sorbet bases, ganache, fondant, and caramel sauce.
Honey and golden syrup are natural or partial invert sugars and work in a pinch, though both bring flavour.
Questions
How do you make invert sugar at home?
Simmer 500 g sugar with 250 ml water and 1/4 tsp cream of tartar (or 1 g citric acid) to about 114 °C / 236 °F, then cool. The acid and heat split part of the sucrose into glucose and fructose; it keeps for months in a sealed jar.
Is honey an invert sugar?
Mostly, yes. Bees add the enzyme invertase, so honey is largely free glucose and fructose. It behaves like invert sugar in recipes but brings its own flavour and some acidity.
Can I use corn syrup instead of invert sugar?
Often. Both interfere with crystallization, but corn syrup is less sweet and less hygroscopic. Use the same weight, expect slightly less sweetness, and slightly less softness in ice cream.
Why is invert sugar sweeter than table sugar?
Fructose tastes much sweeter than sucrose and glucose tastes less sweet. Together they come out roughly 20–30% sweeter than the same weight of sucrose.