Transcript 3. Carbohydrates

Carbohydrates
Simple, Complex, Sugars, “-ose”
Carbohydrates
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Are organic compounds and the body’s main
source of energy
Carbon + hydrogen + oxygen
Our sources of carbohydrates are plants, fruits,
vegetables, grains
Photosynthesis
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Chlorophyll + sunlight = glucose
Plants use carbon dioxide and water and sunlight to
create glucose and oxygen
We eat the glucose, and breathe the oxygen and
release carbon dioxide and water vapor
Chlorophyll is the green pigment in plants
Glucose is the basic sugar molecule from which all
other CHOs are built
A plant can convert glucose into other sugars,
starches and fibers
The Simplest Carbohydrates
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The simplest carbohydrates are the sugars
They are a natural part of many foods
They have a sweet taste
can be extracted from plants and used to sweeten
candy, pop and baked goods
Simple carbohydrates exist in their pure form as
crystalline solids
Eating too many simple sugars can lead to health
problems
Sugars are also called SACCHARIDES
CHO= Sugars + Starches + Fibers
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Simple Sugar Molecule has 6 C, 12 H and 6 O
It is a six sided ring (more stable form)
containing a hydroxyl group (combination of
hydrogen and oxygen containing one atom of
each (OH)
The “-” is a chemical bond that attaches the
group
Linear vs ring glucose
Types of Simple Sugars
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There are two types of simple sugars:
Monosaccharide
Disaccharides
The three examples of monosaccharides are
glucose (buuilding blocks for all other sugars)
fructose (fruits and tree sap) and galactose
(usually bonded to something else…some are
found in milk products)
disaccharides
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Are made from 2 monosaccharides bonded together
Three examples of disaccharides are sucrose (table
sugar), lactose in milk (glucose and galactose stuck
together) and maltose (commonly found in cereals…2
glucose molecules)
ALL carbohydrates (whether simple or complex) are
broken down into monosaccharides when digested
Sucrose- table sugar
Lactose (milk products)
Maltose (cereals)
4 Properties of Sugar
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While sugars have the same chemical formula,
they differ as to how they are positioned in the
molecule ring
The four properties are sweetness,
caramelization, solubility, and crystalization
Property 1- SWEETNESS
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Some sugars are sweeter than others
Order of sweetness: fructose, sucrose, glucose,
galactose, maltose and lactose
The sweetness depends on concentration,
consistency, temperature, and pH level, and
how the molecules fit at the taste bud sites
Sugar in Processed Food
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½ cup of canned corn: 3 tsp
12 oz cola: 8 tsp
1 tbsp ketchup: 1 tsp
1 small yogurt: 7 tsp
2 oz chocolate: 8 tsp
Property 2- Caramelization
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This is the browning reaction that can occur
with any kind of sugar when heated. Sugars
differ at what temperature this occurs
As sugar is heated, water leaves the molecule.
At high temperatures the molecule remnants
join to form larger molecules with a higher
concentration of carbon, which creates the
distinctive caramel color
Property 3: Solubility
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The ability of sugar to dissolve in water mirrors their
sweetness
Order of solubility: fructose (most soluble), sucrose,
glucose, galactose, maltose and lactose
Solubility is affected by water temperature (heat
increases it)
Supersaturation: solution that holds more dissolved
solute than it would normally hold at that temperature
Property 4: Crystallization
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This is beneficial in candy making
Water evaporates increasing the amount of sugar when you are
boiling the sugar solution at high temperatures.
When it reaches a certain temperature, crystallization occurs.
Crystals separate from solution each in a unique pattern of
molecules
The size of the crystals depends on how many particles are
present and how quickly crystals grow around them
A larger # of particles = smaller crystals
Rapidly growing crystals = smaller
Size also depends on the type of sugar (sucrose = large crystals
and glucose and fructose = relatively small)
Sucrose (left) and Fructose crystals
The Complex Carbohydrates:
Starches and Fibres
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Starches: plant foods, taste rather bland, stored
in granular form
Fibre: gives plants their structure (cellulose,
pectins, gums, bran- which is the most
concentrated form of fibre)
There are also peas, lentils, corn, potatoes, dry
beans, grain products (such as rice, pasta and
breads)
Polysaccharides
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Complex CHOs are polysaccharides or large
molecules made of many simple glucose units
Polysaccharides are made of chemically linked
monosaccharides (there may be 10…there may
be 10,000)
A polysaccharide is an example of a
polymer…which is a large molecule formed
when small molecules of the same kind chain
together together
Starches
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Are literally plant food
They are to plants what glycogen is to people
RESERVE ENERGY
Starches are stored in granular form mostly in
seeds and roots
While they are made of chains of sugar
molecules they taste bland because of the type
of glucose they are made of (alpa-D-glucose)
Starches have 2 structures
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A) amylose (in this form of starch the
molecules are linear, the are long and narrow
like a line
B) amylopectin (in this form molecules have
multiple branches like veins in a leaf- typically
more abundant than amylose)
Most starches found in foods have both forms
but in differing proportions
Amylose vs. amylopectin
Another view…
Starches
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Starches are really
important in food
preparation as
thickening agents and
stabilizers
Fiber
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Is not digested by the body
It is what gives plants their structure
The main plant fiber in foods in cellulose
which is a polymer made of alpha-D-glucose
Other edible fibers include hemicellulose,
pectins, and algal polysaccharides
Fiber, continued
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Fiber absorbs water helping to transport food
through the intestines
Fiber is found in whole grains, fresh fruits and
vegetables dried fruits and nuts
In order to digest fiber we need the enzyme
cellulase. We can not synthesize this enzyme
in our digestive tracts so we cant digest fiber,
but ti does add bulk to our diet to help us feel
full and also helps us to clean our intestines
Pectins
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Are water soluble CHOs that occur naturally in
many ripe fruits and vegetables. They produce
a gelatine-like substance used to thicken
jellies. They are also used in food as
emulsifiers and stabilizers in the food industry.
They are very easily oxidated becoming dark.
This is why apples, pears and other fruits
quickly brown after you cut them.