Inverted sugar syrup

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Inverted sugar syrup is sucrose-based syrup treated with the enzyme invertase, and/or an acid, which splits each sucrose molecule into one glucose and one fructose molecule. This combination is sweeter than an equivalent sucrose solution by weight so it can be used to reduce the quantity of sugar in a recipe. It is also more hygroscopic, so it can be used to make a product that stays moist longer than if sucrose was used and is less prone to crystallization. This property is valued especially by bakers, who call the products trimoline or invert syrup.

A familiar, household example of a product that is primarily invert syrup is honey. The process of making jam automatically produces invert sugar by combining the sugar with the acid in the fruit. Inversion can be partial as in products like Golden syrup or complete (100% conversion to glucose and fructose) depending on the functional properties required.

The inversion process is also used in fondant fills for chocolates. The enzyme is added but the filling is enrobed with chocolate before inversion has taken place while still very viscous. The filling then becomes less viscous with time.

Here is the chemical reaction: C₁₂H₂₂O₁₁ (sucrose) + H₂O (water) = C₆H₁₂O₆ (glucose) + C₆H₁₂O₆ (fructose). The acid (or enzyme) enables but is not consumed in the reaction.

Partially inverted sugar syrup can be home-made without the use of enzymes. When making a simple sugar syrup, add about one gram of organic acid, such as citric acid or ascorbic acid, per kilogram of sugar. Cream of tartar or fresh lemon juice can also be used instead. Boiling time needs to be extended to about 20 minutes. This preparation will hydrolyse enough of the sucrose to effectively prevent crystallization, without giving a noticeably sour taste. A way to make an invert sugar syrup without the use of acids or enzymes is to bring a mixture of two parts granulated sucrose and one part water to a boil and then reduce the heat to a low simmer for five to seven minutes until the solution becomes clear.

The word invert comes from the way that sugar syrups rotate plane polarized light. A sucrose or glucose solution rotates light to the right, a fructose syrup rotates it strongly to the left. An equimolar solution of fructose and glucose inverts the rotation of light by rotating it to the left more than the sucrose syrup did to the right.