chemical structure and properties

2.  Carbohydrates consist of the elements
carbon (C), hydrogen (H) and oxygen (O) with
a ratio of hydrogen twice that of carbon and
oxygen.

3. Number of
Carbons
Category Name Examples
4 Tetrose Erythrose, Threose
5 Pentose Arabinose, Ribose, Ribulose,
Xylose, Xylulose, Lyxose
6 Hexose Allose, Altrose, Fructose,
Galactose, Glucose, Gulose,
Idose, Mannose, Sorbose, Talose,
Tagatose
7 Heptose Sedoheptulose, Mannoheptulose

4. D-erythrose D-Threose

5. D-Ribose D-Arabinose

6. D-Gulose D-Idose

7. D-Sedoheptulose D-Mannoheptulose

8. Disaccharide Description Component
monosaccharide
sucrose common table sugar glucose 1α→2
fructose
maltose product of starch
hydrolysis
glucose 1α→4
glucose
lactose main sugar in milk galactose 1β→4
glucose

11.  Many polysaccharides, unlike sugars, are insoluble in
water.
 Dietary fiber includes polysaccharides and
oligosaccharides that are resistant to digestion and
absorption in the human small intestine but which are
completely or partially fermented by microorganisms
in the large intestine.

12.  Starch is the major form of stored carbohydrate in
plants. Starch is composed of a mixture of two
substances: amylose, an essentially linear
polysaccharide, and amylopectin, a highly branched
polysaccharide.
Amylose

13.  Amylopectin: Amylopectin differs from
amylose in being highly branched. Short side
chains of about 30 glucose units are attached
with 1α→6 linkages approximately every
twenty to thirty glucose units along the chain.
Amylopectin molecules may contain up to two
million glucose units.

14.  Glucose is stored as glycogen in animal tissues by the
process of glycogenesis. When glucose cannot be
stored as glycogen or used immediately for energy, it
is converted to fat.

17.  It is common for individuals to associate sugar (sucrose) with its
inherent taste properties.
 Aside from providing a sweet taste and flavour, sugar imparts
numerous functional properties that make it an important ingredient
in many foods.
 Specific functional properties of sugar can be classified into four
broad categories: sensory, physical, microbial and chemical

18.  Taste - Sweetness is generally the most recognized functional property of
sugar.
 Caramelization - is a browning reaction that results from the action of heat
on sugars. At high temperatures, the chemical changes associated with
melting sugars result in a deep brown colour and new flavours.
 Flavour - Flavours result when tastes (sweet, sour, bitter, salty) are
combined with sense of smell when food is consumed.
 Texture - Sugar makes an important contribution to the way we perceive
the texture of food. For example, adding sugar to ice-cream provides body
and texture which is perceived as smoothness.

19.  Tenderizer - Sugar acts as an important tenderizing agent in
foods such as baked products. During the mixing process,
sugar compete with other ingredients for water.
 Maillard Reaction - results from chemical interactions
between sugars and proteins at high heat. An amino group
from a protein combines with a reducing sugar to produce a
brown colour in a variety of foods (e.g. brewed coffee, fried
foods, milk & breads).
 Appearance - Sugar is responsible for the yellow-brown
colours that develop in baked foods. Sucrose itself develops
colour through caramelization.

20.  Solubility - Sugar is easily soluble in water. The ability to produce
solutions of varying sugar concentrations is important in many food
applications.
A high level of solubility, for example, is essential in beverages to provide
sweetness and to increase viscosity to create a desirable ‘mouthfeel'.
 Freezing Point - Sugar is effective in lowering freezing points. Freezing
point depression is an important property in ice-creams, frozen desserts
and freeze-dried foods to ensure the development of fine crystal structure
and product smoothness.
 Boiling Point - The concentration of sugar in a solution affects the boiling
point by raising it. This characteristic is important in candy manufacture as
boiling point elevation allows for more sugar to be dissolved in solution,
creating a ‘super saturated' and more concentrated solution.

21.  Preservation - Sugar plays a role in the preservation of
many food products. The addition of sugar to jams and
jellies, for example, inhibits microbial growth and
subsequent spoilage.
 Fermentation - Sugar is extremely important in the
baking and brewing industries. Yeasts use sugars as food
to produce ethanol, carbon dioxide and water through the
process of fermentation.

22.  Antioxidant Activity - Sucrose has been reported to exhibit
antioxidant properties which help to prevent the deterioration of
textures and flavours in canned fruits and vegetables.
 In addition, the products of the hydrolysis of sucrose (glucose and
fructose) appear to have the ability to block the reactive sites of ions
such as copper and iron and, to a lesser extent, cobalt. This
characteristic of monosaccharides aids in food preservation by
delay catalytic oxidation reactions.