Simple sugar of monosaccharides

The two main types of sugars are monosaccharides and disaccharides. Monosaccharides consist of a single sugar molecule.

Monosaccharides may contain from three to nine carbon atoms although most of them contain five or six. A three carbon monosaccharide is called a triose; one containing four carbons is called a tetrose; five, a pentose; six, a hexose; seven, a heptose; eight an octose and nine a nonose.

α- D -glucose

*Pentoses (Arabinose, ribose, xylose) The pentose sugars, deoxyribose and ribose, are essential components of the genetic material DNA and RNA. E.g. glucose and fructose: (C6H12O6); arabinose and xylose: (C5H10O5).

Arabinose is found in gums and when several arabinose molecules are joined together, a pentosan formed.

*Hexoses
-Aldohexoses – galactose, glucose
-Ketohexose - fructose
 All hexoses have the same chemical formula C6H12O6, but slightly different structures. In nature, only fructose and glucose occur in free form. Galactose joined with glucose forms the disaccharide lactose.

Glucose is a hexose. Octoses and nanoses are quite rare. Glucose, the main source of energy for body cells, is found in most sweet fruits and in blood.
Simple sugar of monosaccharides

Fructose as a sweetener

Fructose is so efficient in its sweetening power that is common in commercially prepared foods today as sucrose.

It is a sweetener that is found naturally in fresh fruit and honey. Fructose is a monosaccharide, with five carbon furanose ring structure rather than the six carbon pyranose ring structure of glucose.

Its chemical structure has highly reactive molecules which bind to protein molecules. Fructose is known as fruit sugar or laevulose.

Fructose was first extracted from cane sugar more than a century ago, and it’s found in varying amounts in such fruits as apples, grapes, orange and berries.

Fructose is low in glycemic index, meaning that it releases glucose in to the bloodstream slowly.  Fructose produces liver glycogen rapidly making it a more efficient supply than other sweetener.

Fructose is the sweetest natural saccharide and is approximately 1-1.5 times as sweet as sucrose. It is also water soluble.

Fructose metabolizes at a slow rate, helping to control insulin surges. It is recommended for diabetics and others seeking to control their carbs.

It is in baked goods because it reacts with amino acids to produce a browning reaction. It is used as a nutritive sweetener in low-calorie beverages.

Fructose can be the sweetener of choice in a weight loss diet. Fructose also seems to make eaters pick foods with less fat. 

In dental health studies, less dental plaque was reported with fructose than with sugar.

Some plants including chicory Jerusalem artichokes and dahlias contain appreciable quantities of the polysaccharide inulin, which is a polymer of fructose.
Fructose as a sweetener

The Sweetness of Sugar

Sweetness is a taste which is generally pleasing to humans as well as to many other animals. Sweetness is found in many forms, the most common being the simple sugars.

In United States, the natural sugars of milk, fruits, vegetables, and grains account for about half of the sugar intake, the other half consists of concentrated sugars that have been refined and added to foods for a variety of purposes.

Sugars, important in nutrition, consist of monosaccharides, having the general formula C6H12O6, and disaccharides, having the general formula C12H22O11.

Although the monosaccharides consists of 3-carbon sugars (trioses), 4-carbon sugars (tetroses), 5-carbon sugars (pentoses), and 6-carbon sugars (hexoses), only the latter are important in human nutrition as sources of energy.

Three monosaccharides are important in nutrition: glucose, fructose and galactose. All three monosaccharides have the same number and kinds of atoms but in different arrangements.

Glucose, a 6-carbon sugar, is one of the simplest carbohydrates found in foods. While many foods contain traces of glucose, it is found in significant amounts only in fruits, such as grapes.

Most cells depend on glucose for their fuel to some extent and the cells of the brain and the rest of the nervous system depend almost exclusively on glucose for their energy.

Fructose, also a 6-carbon sugar, is found in ripened fruits and honey, both of these sugars can be utilizes by body as a source of energy. It is the sweetest of the natural sugars.

Other source of fructose include soft drinks, ready to eat cereals and other products sweetened with high fructose corn syrup.

Lactose, the 12-carbon sugar present in milk, is broken down in the intestine to glucose and lactose (6-carbon sugar), both of which can be used as sources of energy.

Maltose, another disaccharide, produced form starch in the malting of grains is much less effective sweetener than sucrose.

The used of added sugars had risen steadily over the past several decades, both in the United States and around the world, with soft drinks and sugared fruit drinks accounting for most of the increase.
The Sweetness of Sugar