Inverted sugar syrup
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Inverted sugar syrup is a sucrose-based syrup produced with the glycoside hydrolase enzyme invertase or an acid, which splits each sucrose disaccharide molecule into its component glucose and fructose monomer molecules; one of each. In practical terms measured on equivalent dissolved weights invert syrups are sweeter than sucrose solutions. However invert sugar is 85% the sweetness of an equivalent concentration of sucrose solution; inverting a disaccharide effectively doubles the concentration of sugar molecules.[1] Invert sugar's glucose is substantially more hygroscopic than sucrose, so it lends longer lasting moistness to products than when sucrose is used alone. It is likewise less prone to crystallization and valued especially by bakers, who refer to inverted sugar syrup as trimoline or invert syrup.
The term invert comes from the method used for measuring sugar syrups. Plane polarised light passed through a sample of pure sucrose solution is rotated (optical rotation). As the solution is converted to a mixture of sucrose, fructose and glucose, the amount of rotation is reduced and the light appears inverted compared to light passed through the sucrose solution.
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[edit] Chemical Reaction
C12H22O11 (sucrose) + H2O (water) = C6H12O6 (glucose) + C6H12O6 (fructose)
An acid or enzyme enables, but is not consumed in, the reaction. The rate of the reaction depends on temperature and concentration of the reactants, with more concentrated solutions requiring more time to achieve a given conversion at a given temperature. Elevated temperature speeds the conversion for acid type reactions, but does not for enzymatic conversion above the temperature of maximum activation. (This paradoxical aspect of enzymatic conversion allows the fondant to be strongly heated, softening the fondant for forming. Upon cooling, it hardens. Only after being coated with chocolate are the candies raised in temperature to the enzyme activation point. The invert sugar is produced in-situ.)
[edit] Making Invert Sugar
Inverted sugar syrup can be easily made by adding roughly one gram of citric acid or ascorbic acid, per kilogram of sugar. Cream of tartar (one gram per kilogram) or fresh lemon juice (10 milliliters per kilogram) may also be used (1 tsp lemon juice per 1 pound sugar).
The mixture is boiled for 20 minutes, and will convert enough of the sucrose to effectively prevent crystallization, without giving a noticeably sour taste. Invert sugar syrup may also be produced without the use of acids or enzymes by thermal means alone: two parts granulated sucrose and one part water simmered for five to seven minutes will convert a modest portion to invert sugar.
All invert syrups are created by hydrolysing sucrose to glucose (dextrose) and fructose by heating a sucrose solution, then relying either on time alone, or time and the catalysis reaction of an acid or enzymes to speed the reaction. Commercially prepared acid catalyzed solutions are neutralised when the desired level of inversion is reached.
All constituent sugars (sucrose, glucose and fructose) support fermentation, so invert sugar solutions may be fermented as readily as sucrose solutions.
[edit] Shelf Life
Invert sugar has a lower water activity than that of sucrose, so provides more powerful preserving qualities (shelf life) to products that utilize it.
The shelf life of partial inverts is approximately six months, depending on storage and climatic conditions. Crystalized invert sugar solutions may be restored to their liquid state by gently heating.
[edit] Examples
- Toffee
- Honey is a mixture principally of glucose and fructose giving it similar properties to invert syrup, which affords it its remarkable ability to remain liquid for long periods of time.
- Jam, when made, produces invert sugar by the action of the fruit's acid and extended heating.
- Golden syrup is a syrup of approximately 56% invert syrup and the remainder sucrose.
- Fondant filling for chocolates is unique in that the conversion enzyme is added but not activated 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.
- York Peppermint Patties contain invert sugar.
[edit] References
[edit] Notes
[edit] General references
- Carbohydrates. Carbohydrates. Retrieved on 2006-05-01.
- Making simple syrup is an exercise in chemical reactions. A Word from Carol Kroskey. Retrieved on 2006-05-01.
- Frequently Asked Questions - Cookies. AIB International. Retrieved on 2006-05-01.
