Inverted sugar syrup is a syrup mixture of the monosaccharides glucose and fructose, made by splitting the disaccharide sucrose. This mixture's optical rotation is opposite to that of the original sugar, which is why it is called an invert sugar. Splitting is completed through hydrolytic saccharification. It is 30% sweeter than table sugar, and foods that contain invert sugar retain moisture better and crystallize less easily than those that use table sugar instead. Bakers, who call it invert syrup, may use it more than other sweeteners. Other names include invert sugar, simple syrup, sugar syrup, sugar water, bar syrup, and sucrose inversion.
Production
Additives Commercially prepared enzyme-catalyzed solutions are inverted at 60 °C (140 °F). The optimum pH for inversion is 5.0. Invertase is added at a rate of about 0.15% of the syrup's weight, and inversion time will be about 8 hours. When completed the syrup temperature is raised to inactivate the invertase, but the syrup is concentrated in a vacuum evaporator to preserve color. Though inverted sugar syrup can be made by heating table sugar in water alone, the reaction can be sped up by adding lemon juice, cream of tartar, or other catalysts, often without changing the flavor noticeably. Common sugar can be inverted quickly by mixing sugar and citric acid or cream of tartar at a ratio of about 1000:1 by weight and adding water. If lemon juice, which is about five percent citric acid by weight, is used instead then the ratio becomes 50:1. Such a mixture, heated to 114 °C (237 °F) and added to another food, prevents crystallization without tasting sour. Commercially prepared hydrochloric acid-catalyzed solutions may be inverted at the relatively low temperature of 50 °C (122 °F). The optimum pH for acid-catalyzed inversion is 2.15. As the inversion temperature is increased, the inversion time decreases. They are then given a pH neutralization when the desired level of inversion is reached. In confectionery and candy making, cream of tartar is commonly used as the acidulant, with typical amounts in the range of 0.15–0.25% of the sugar's weight. The use of cream of tartar imparts a honey-like flavor to the syrup. After the inversion is completed, it may be neutralized with baking soda using a weight of 45% of the cream of tartar's weight.
For fermentation
All constituent sugars (sucrose, glucose, and fructose) support fermentation, so invert sugar solutions of any composition can be fermented. Syrup is used to feed microbiological life, which requires oxygen found in the water. For example, kombucha is produced by fermenting inverted sugar syrup with tea using a symbiotic culture of bacteria and yeast (SCOBY), and yeast in winemaking is used for ethanol fermentation. Cold water can hold more dissolved oxygen than warm water, but granulated sugar does not dissolve easily in cold water. Water in a container with wide bottom surface area allows for faster dissolving of the sucrose, which only has to be mixed a few times periodically to form a homogeneous solution. Also, a mixer or blender may be used to rotate the sugar, in turns, if necessary.
In other foods and products
Honey is mostly a mixture of glucose and fructose similar to invert syrup and can therefore remain a liquid for longer periods of time. Jam contains invert sugar formed by the heating process and the acid content of the fruit. This sugar preserves the jam for long periods of time. Golden syrup is a syrup of about 55% invert syrup and 45% table sugar (sucrose). Fondant filling for chocolates is unique in that the conversion enzyme is added, but not activated by acidification (microenvironment pH adjustment) or cofactor addition depending on the enzymes, before the filling is enrobed with chocolate. The very viscous (and thus formable) filling then becomes less viscous with time, giving the creamy consistency desired. This results from the sub-optimal enzymes conditions purposely created by withholding activation factors, which allows only a fraction of the enzymes to be active, or allows all enzymes to proceed at only a fraction of the biological rate [biologically, it's realistically a combination of both: a reduced number of functional enzymes, with the ones that do function having reduced catalytic kinetics/rates]. Cadbury Creme Eggs are filled with inverted sugar syrup produced by processing fondant with invertase. Sour Patch Kids also contain inverted sugar to add sweet flavor.
Sweetened beverages Inverted sugar syrup is the basis in sweetened beverages.
Sweet reserve is a wine term referring to a portion of selected unfermented grape must, free of microorganisms, to be added to wine as a sweetening component. When wine ferments, glucose is fermented at a faster rate than fructose. Thus, arresting fermentation after a significant portion of the sugars have fermented results in a wine where the residual sugar consists mainly of fructose, while the use of sweet reserve will result in a wine where the sweetness comes from a mixture of glucose and fructose. Alcoholic beverage manufacturers often add invert sugar in the production of drinks like gin, beer, and sparkling wines for flavoring. Candi sugar, similar to invert sugar, is used in the brewing of Belgian-style beers to boost alcohol content without drastically increasing the body of the beer; it is frequently found in the styles of beer known as dubbel and tripel.
Chemistry
Table sugar (sucrose) is converted to invert sugar by hydrolysis. Heating a mixture or solution of table sugar and water breaks the chemical bond that links together the two simple-sugar components. The balanced chemical equation for the hydrolysis of sucrose into glucose and fructose is:
C12H22O11 (sucrose) + H2O (water) → C6H12O6 (glucose) + C6H12O6 (fructose)
Optical rotation After a sucrose solution has had some of its sucrose turned into glucose and fructose the solution is no longer said to be pure. The gradual decrease in purity of a sucrose solution as it is hydrolyzed affects a chemical property of the solution called optical rotation that can be used to figure out how much of the sucrose has been hydrolyzed and therefore whether the solution has been inverted or not.
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