1. Food Biotechnology Dr. Tarek Elbashiti Food Biochemistry 1 Carbohydrates

2. Carbohydrates Comprised of > 90% of dry matter of plants
Abundant, widely available and inexpensive
Common components of food
As natural components and added ingredients
Commonly consumed in quantities and varieties of products
Different molecular structures, size and shape
Exhibit variety of chemical and physical properties
Therefore amendable in both chemical and biochemical modification to improve properties and extending uses

3. Chemical nature

4. Classification Monosaccharides Disaccharides Oligosaccharides
Polysaccharides
Starch
Dietary fibre

6. (Carbonyl) 1 1 2

7. Aldose and ketose Aldose: An aldehyde Ketose: A ketone
is an organic compound containing a terminal carbonyl group. This functional group, which consists of a carbon atom which is bonded to a hydrogen atom and double-bonded to an oxygen atom (chemical formula O=CH-).
Also called the formyl or methanoyl group.
Ketose:
A ketone
either the functional group characterized by a carbonyl group (O=C) linked to two other carbon atoms or a chemical compound that contains the functional group.

8. Glucose
Fructose
Galactose

9. `

14. Disaccharides 2 monosaccharide units joined together 2 sugar units
Maltose
2 glucose units (α 1-4 linkages)
Cellobiose
2 glucose units (β 1-4 linkages)
Lactose
Galactose + glucose (β 1-4 linkages)
Sucrose
Glucose + fructose (α 1-2 linkages

15. Glycosidic Bonds
Formed between the free carbonyl group of one monosaccharide and a hydroxyl group of another monosaccharide
Readily hydrolyzed by
Heat and acid
Certain enzymes such as sucrase,invertase, amalyaes

16. Maltose also known as malt sugar
actual name = 4-O-(a -D-glucopyranosyl)- a -D-glucopyranose
obtained by enzyme-catalyzed hydrolysis of starch
composed of two D-glucopyranoses
1,4’-a -glycoside bond (1,4’-a -linkage)
reducing sugar, contains hemiacetal function and can mutarotate
easily digested by humans

19. The lack of the Sucrase-Isomaltase enzyme, causes sucrose and maltose intolerance and is called Congenital Sucrase-Isomaltase Deficiency.
This congenital disorder is most prominent in infancy but can develop later in life.
One can notice that a patient suffers from this pathology when they have “stomach cramps, bloating, excess gas production, nausea, vomiting and diarrhea.
Upper respiratory tract and viral infections are common.
These digestive problems can lead to lower than normal weight gain and growth.

20. Lactose milk sugar (both human and cow)
actual name = 4-O-(b -D-galactopyranosyl)-b -D-glucopyranose
milk sours when lactose is converted to lactic acid (tastes sour)
composed of D-galactose and D-glucose
1,4’-b -glycoside bond (1,4’-b -linkage)
digested by most humans, lactose intolerant individuals often lack the enzyme, lactase, which hydrolyzes the glycosidic linkage. If a person becomes lactose intolerant, they often they quit producing lactase, or it becomes ineffective.
reducing sugar

24. Sucrose Table sugar (from sugar beets or sugar cane)
actual name = 2-O-(a -D-glucopyranosyl)-b -D-fructofuranoside
composed of one glucose and one fructose molecule
"invert sugar" is produced by the hydrolysis of sucrose. The hydrolysis produces a 1:1 mixture of glucose:fructose. This is called "invert sugar" because the optical rotation changes from +66.5o to -22.0o upon hydrolysis.
1.2’-glycoside linkage (beta-D-fructoside and alpha-D-glucoside)
not a reducing sugar, no free hemiacetal, this implies both glucose and fructose must be glycosides

27. Reducing Sugars Contain a free carbonyl group
All monosaccharides are reducing sugars
Disaccharides are reducing sugars only if they contain a free carbonyl group
Sucrose is not a reducing sugar-carbonyl group of both glucose and fructose is involved in the glycosidic bond.
Reducing sugars give brown colors to baked goods when they combine with free amino acids-Maillard reaction.

28. Oligosaccharides 3-10 sugar units Important oligosaccharides
raffinose and stachyose.
Composed of repeating units of galactose, glucose and fructose
nutritional importance because they are found in beans and legumes.
unique glycosidic bonds
raffinose and stachyose cannot be broken down into their simple sugars.
therefore, they cannot be absorbed by the small intestine and are often metabolized by bacteria in the large intestine to form unwanted gaseous byproducts.
commercial enzyme preparations such as Beano can be consumed before a meal rich in beans and legumes in order to aid the small intestine in the breakdown of these oligosaccharides.

31. Polysaccharides or complex carbohydrates
More than 10 units of sugar
Usually monomers and consist of thousands of repeating glucose units.
Allow for the storage of large quantities of glucose.
Starch is the major storage form of carbohydrate in plants and has two different types: amylose and amylopectin.
Although digestible alpha glycoisidic bonds link both types of starch, each type is unique in their branching of glucose.
amylose is a straight chain polymer
amylopectin is highly branched.
These differences account for the fact that
amylopectin can form stable starch gels which are able to retain water
while amylose is unable to do so.
Therefore, amylopectin is often used by manufacturers to produce many different kinds of thick sauces and gravies. Sources of starch include potatoes, beans, bread, pasta, rice and other bread products.

35. Amylose several hundred glucose molecules with 1,4’-a -glycoside bonds
molecular weight of 150,000 to 600,000
1000 to 4000 glucose units per molecule
little or no branching
chains coil in the form of a helix. In the Iodine test, I2 molecules fit into the helix and causes the intense blue color

37. Amylopectin more complex than amylose
1,4’-a -glucose linkages for the main polysaccharide chain
1,6’-a glycoside linked branches approximately every 25 units
very complex 3-d structure
up to 1 million glucose units per molecule

39. Indigestible polysaccharides
Dietary fiber and come in many different forms including cellulose, hemicellulose, pectin, gum and mucilage.
Cellulose is by far the most abundant biochemical compound on the earth
because it forms part of the structure of many plants.
unique among polysaccharides in that it forms intramolecular hydrogen bonds between adjacent glucose units as well as beta 1,4 glycosidic bonds present in other carbohydrates.
these special bonding characteristics allow cellulose to form long, straight chains of glucose and give it strength and rigidity that many plants require for proper growth.
Cellulose and most forms of hemicellulose are insoluble fibers while pectin, gum and mucilage are all soluble fibers and readily dissolve or swell when mixed with water.

41. Tutorial Define the following and give an example of each:
Monosaccharides
Disaccharides
Polysaccharides
2.Differentiate between:
aldose and ketoses.
Amylose and amylopectin
3. What is lactose intolerance?
4. Why can’t we use galactose?
5. What is galactosemia?