Food Biotechnology - PowerPoint Presentation

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Food Biotechnology

Dr.

Kamal

E. M.

Elkahlout

Food Biochemistry 1 CarbohydratesSlide2

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 usesSlide3

Chemical natureSlide4

Classification

Monosaccharides

Disaccharides

Oligosaccharides

Polysaccharides

Starch

Dietary fibreSlide5
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(Carbonyl)

1

1

2Slide7

Aldose and ketose

Aldose:

An

aldehyde

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. Slide8

Glucose

Fructose

GalactoseSlide9
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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 linkagesSlide13

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, amalyaesSlide14

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 humansSlide15
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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 Slide18
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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 Slide22
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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.Slide25

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. Slide26
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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. Slide29
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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 colorSlide33
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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 Slide35
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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. Slide37
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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?