Fructose

OVERVIEW

Fructose (FROOK-tose) is a white crystalline solid found in honey and certain fruits and vegetables. It is the sweetest of the common sugars. Fructose is a carbohydrate, an organic compound in which five of the six carbon atoms are arranged in a ring to which are attached the hydrogen atoms and hydroxy (−OH) groups that make up the molecule. It is classified as a monosaccharide ("one sweet substance"), in contrast to sucrose, common table sugar, which is classified as a disaccharide ("two sweet substances"). Molecules of sucrose consist of two rings rather than the one ring found in fructose.

KEY FACTS

OTHER NAMES:

D-Fructose; fruit sugar

FORMULA:

C₆H₁₂O₆

ELEMENTS:

Carbon, hydrogen, oxygen

COMPOUND TYPE:

Carbohydrate (organic)

STATE:

Solid

MOLECULAR WEIGHT:

180.16 g/mol

MELTING POINT:

103°C (217°F); decomposes

BOILING POINT:

Not applicable

SOLUBILITY:

Very soluble in water and acetone; soluble in ethyl alcohol and methyl alcohol

HOW IT IS MADE

Fructose is produced commercially by the hydrolysis of beet sugar or inulin, a polysaccharide found in the roots of a number of plants, including dahlias, Jerusalem artichokes, and chicory. Hydrolysis is the process by which a material is broken down into simpler elements by reacting it with water. A polysaccharide is a carbohydrate with many simple sugar groups attached to each other. After hydrolysis of the beet sugar, or inulin, the resulting mixture is treated with lime (calcium oxide; CaO) to extract the fructose. It is then refined by removing impurities left from the preparation process.

COMMON USES AND POTENTIAL HAZARDS

Virtually the only important use of fructose is as a sweetener and preservative in a number of food products. In most cases, it is now used in the form of a substance known as high-fructose corn syrup (HFCS). HFCS was first introduced in the 1970s after scientists at the Clinton Corn Processing Company in Clinton, Iowa, developed a method of converting the sugar in corn into glucose and fructose. The Clinton process is relatively complicated. The polysaccharides in corn are first converted to glucose, and the glucose is then treated with enzymes that convert it to a thick syrup consisting of roughly half glucose and half fructose. From a nutritional standpoint, HFCS is very similar to sucrose, common table sugar, but it is less expensive to produce than sucrose and is more convenient to use in many instances.

High-fructose corn syrup has become one of the great success stories in the recent history of food processing in the United States. It has replaced sucrose in many applications, including nearly all soft drinks and fruit beverages, and in many jams and jellies, cookies, gum, baked goods, and other processed foods. Consumption of HFCS in the United States has increased from about 2 million metric tons (2.2 million short tons) in 1980 to just over 8 million metric tons (8.8 million short tons) in 2000.

Interesting Facts

• Sucrose is a disaccharide that consists of one molecule of glucose joined to one molecule of fructose. The first step in the digestion of sucrose is the hydrolysis of the molecule, resulting in the formation of one molecule of glucose and one molecule of fructose. These compounds are the primary materials used by the human body in producing the energy needed to stay alive and grow.

When high-fructose corn syrup was first introduced, experts in nutrition did not anticipate that any health problems would be associated with the new product. After all, both fructose and glucose are naturally occurring substances that humans have been consuming for millennia. They are not so sure any more. Some evidence suggests that fructose is metabolized differently in the body than is glucose. It is not converted to energy as efficiently and may actually act more like a fat than like a sugar. Since few studies have been conducted on the ultimate chemical fat of fructose in the body, the nutritional value of HFCS is still the subject of some controversy among experts.

The dangers of consuming HFCS are apparent for at least one group of people, those who lack the enzyme needed to metabolize fructose properly. Individuals with this genetic disorder may develop serious reactions if exposed to even a very small amount of fructose, reactions that include sweating, nausea, vomiting, confusion, abdominal pain, and, in extreme cases, convulsion and coma. Fortunately, this disorder is quite rare, affecting one person in about every twenty thousand individuals. For those with the disorder, however, care must be used in the kinds of sweeteners included in the diet.

Words to Know

HYDROLYSIS

The process by which a compound reacts with water to form two new compounds

FOR FURTHER INFORMATION

Basciano, Heather, Lisa Federico, and Khosrow Adeli. "Fructose, Insulin Resistance, and Metabolic Dyslipidemia." Nutrition and Metabolism. (Electronic journal) http://www.nutritionandmetabolism.com/content/2/1/5 (accessed on October 10, 2005).

Ophardt, Charles E. "Fructose." Elmhurst College. http://www.elmhurst.edu/∼chm/vchembook/543fructose.html (accessed on October 10, 2005).

Squires, Sally. "Sweet but Not So Innocent?" Washington Post. (March 11, 2003): HE01. Available online at http://www.washingtonpost.com/ac2/wp-dyn/A8003-2003Mar10?language=printer (accessed on October 10, 2005).

"What Do We Know about Fructose and Obesity?" The International Food Information Council. http://www.ific.org/foodinsight/2004/ja/fructosefi404.cfm (accessed on October 10, 2005).

See AlsoGlucose; Sucrose

fructose Also known as fruit sugar or laevulose. A six‐carbon monosaccharide sugar (hexose) differing from glucose in containing a ketone group (on carbon‐2) instead of an aldehyde group (on carbon‐1). Found as the free sugar in fruits and honey, and as a constituent of the disaccharide sucrose (together with glucose). It is 1.7 times as sweet as sucrose. Commercially prepared by the hydrolysis of the polysaccharide inulin from the Jerusalem artichoke. See also invert sugar.

fructose (fruit sugar; laevulose) A simple sugar, C₆H₁₂O₆, stereoisomeric with glucose (see monosaccharide). (Although natural fructose is the D-form, it is in fact laevorotatory.) Fructose occurs in green plants, fruits, and honey and tastes sweeter than sucrose (cane sugar), of which it is a constituent. Derivatives of fructose are important in the energy metabolism of living organisms. Some polysaccharide derivatives (fructans) are carbohydrate energy stores in certain plants.

fructose (fruit sugar, C₆H₁₂0₆) Simple white monosaccharide, found in honey, sweet fruits, and flower nectar. Sweeter than sucrose, it is made commercially by the hydrolysis of beet or cane sugar, and is used in foods as a sweetener. Its derivatives play a crucial role in providing energy for organisms.

fructose (D-fructose, levulose, C₆H₁₂O₆) A sugar that occurs abundantly in nature as the free form; but also, with glucose, in the form of the disaccharide sucrose.