Invert sugar (also known as inverted sugar) is sucrose partially or totally cleaved into fructose and glucose (also known dextrose) and, apart from the chemical process used (see below), the obtained solution has the same amount of the two carbohydrates.
Moreover, according to the product, not cleaved sucrose may also be present.
Invert sugar production
The breakdown of sucrose may happen in a reaction catalyzed by enzymes, such as:
- sucrase, active at our own intestinal level where it is involved in carbohydrate digestion;
- invertase, an enzyme secreted by honeybees into the honey and used industrially to obtain invert sugar.
Another process applies acid action, as it happens partly in our own stomach and as it happened in the old times, and still happens, at home-made and industrial level. Sulfuric and hydrochloric acids was used, heating the solution with caution for some time; in fact the reaction is as fast as the solution is acid, regardless of the type of acid used, and as higher the temperature is. The acidity is then reduced or neutralized with alkaline substances, as soda or sodium bicarbonate.
A chemical process as described occurs when acid foods are prepared; i.e. in the preparation of jams and marmalades, where both conditions of acidity, naturally, and high temperatures, by heating, are present. The situation is analogous when fruit juices are sweetened with sucrose.
The reaction develops at room temperature as well, obviously more slowly.
What is the practical outcome of that?
It means that, during storage, also sweets and acid foods, even those just seen, go towards a slow reaction of inversion of contained/residue sucrose, with consequent modification of the sweetness, since invert sugar at low temperatures is sweeter (due to the presence of fructose), and assumption of a different taste profile.
Properties and uses
It is principally utilized in confectionery and ice-cream industries thanks to some peculiar characteristics.
- It has an higher affinity for water (hydrophilicity) than sucrose (see fructose) therefore it keeps food more humid: e.g. cakes made with invert sugar dry up less easily.
- It avoids or slows down crystal formation (dextrose and fructose form less crystals than sucrose), property useful in confectionery industries for icings and coverage.
- It has a lower freezing point.
- It increases, just a bit, the sweetness of the product in which it has been added, as it is sweeter than an equal amount of sucrose (the sweetness of fructose depends on the temperature in which it is present).
- It may take part to Maillard reaction (sucrose can’t do it) thus contributing to the color and taste of several bakery products.
It should be noted that honey, lacking in sucrose, has a fructose and glucose composition almost equal to that of 100% invert sugar (fructose is slightly more abundant than glucose). So, diluted honey, better if not much aromatic, may replace industrial invert sugar.
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- Bender D.A. “Benders’ Dictionary of Nutrition and Food Technology”. 8th Edition. Woodhead Publishing. Oxford, 2006
- Jordan S. Commercial invert sugar. Ind Eng Chem 1924;16(3):307-310. doi:10.1021/ie50171a037
- Stipanuk M.H., Caudill M.A. Biochemical, physiological, and molecular aspects of human nutrition. 3rd Edition. Elsevier health sciences, 2012