Fructose

From plant sources, tree and vine fruits, flowers, berries and most root vegetables. In plants, fructose may be present as the monosaccharide and/or as a component of sucrose. Fructose is also found in honey. Commercially, fructose is usually derived from sugar cane, sugar beets and corn.
 * Fructose**, or fruit sugar, is a simple monosaccharide found in many plants. It is one of the three dietary monosaccharides, along with glucose and galactose, that are absorbed directly into the bloodstream during digestion. Fructose was discovered by French chemist Augustin-Pierre Dubrunfaut in 1847 . Pure, dry fructose is a very sweet, white, odorless, crystalline solid and is the most water-soluble of all the sugars.

Is metabolized in the liver and too much fructose in the liver can lead to weight gain as well as fatty liver diseases.

Classified as the sweetest of all sugars.







Chemical properties
   **Figure 1:** Relationship between the acyclic and the cyclic ( hemiketal ) isomers of fructose. d - and l -isomers of fructose (open-chain form) Fructose is a 6-carbon polyhydroxyketone. It is an isomer of glucose ; i.e., both have the same molecular formula ( C 6 H 12 O 6) but they differ structurally. Crystalline fructose adopts a cyclic six-membered structure owing to the stability of its hemiketal and internal hydrogen-bonding. This form is formally called D-fructopyranose. In solution, fructose exists as an equilibrium mixture of 70% fructopyranose and about 22% fructofuranose, as well as small amounts of three other forms, including the acyclic structure.

Fructose and fermentation
Fructose may be anaerobically fermented by yeast or bacteria. Yeast enzymes convert sugar (glucose, or fructose) to ethanol and carbon dioxide. The carbon dioxide released during fermentation will remain dissolved in water, where it will reach equilibrium with carbonic acid, unless the fermentation chamber is left open to the air. The dissolved carbon dioxide and carbonic acid produce the carbonation in bottle fermented beverages.

Fructose and Maillard reaction
Fructose undergoes the Maillard reaction, non-enzymatic browning, with amino acids. Because fructose exists to a greater extent in the open-chain form than does glucose, the initial stages of the Maillard reaction occurs more rapidly than with glucose. Therefore, fructose potentially may contribute to changes in food palatability, as well as other nutritional effects, such as excessive browning, volume and tenderness reduction during cake preparation, and formation of mutagenic compounds.

Dehydration
Fructose readily dehydrates to give hydroxymethylfurfural ("HMF"). This process may in the future be part of a low-cost, carbon-neutral system to produce replacements for petrol and diesel from plantations.

Pure crystalline fructose has had a negligible effect on the carbohydrate composition of the diet because of the small volume of this sugar produced relative to all other naturally occurring and added starches, syrups and sweeteners.

Benefits: Fructose does not hydrolyze in acidic conditions like sucrose does; so finished product sweetness and flavor are stable over extended storage times. [|Fructose] maintains the integrity of frozen fruit by controlling water and preventing damaging ice crystal formation that can destroy fragile fruit tissue Fructose has a [|low glycemic index] and results in moderate release of insulin to the bloodstream relative to glucose and sucrose.

Fructose is one of the 4 D-Ketohexoses