polysaccharide, starch, pectin & cellulose functions & uses

1. polysaccharides
(starch, pectin and cellulose)

2. Starch
OCCURRENCE, ISOLATION
• Starch is widely distributed in various plant organs as a storage
carbohydrate.
• As an ingredient of many foods, it is also the most important
carbohydrate source in human nutrition.
• In addition, starch and its derivatives are important industrially,
for example, in the paper and textile industries.
• Starch obtained from com, potatoes, cassava, and wheat in the
native and modified form accounted for 99 % of the world
production in 1980.
• Some other starches are also available commercially.
• Recently, starches obtained from legumes (peas, lentils) have
become mor interesting because they have properties which
appear to make them a suitable substitute for chemically modified
starches in a series of products.

3. • Starches of various origin have individual, characteristic properties which go back to the shape,
size, size distribution, composition, and crystallinity of the granules.
• The existing connections are not yet completely understood on a molecular basis.
• In some cases, e.g., potato tubers, starch granules occur free, deposited in cell vacuoles; hence,
their isolation is relatively simple.
• The plant material is disintegrated, the starch granules are washed out with water, and then
sedimented from the "starch milk" suspension and dried.
• In other cases, such as cereals, the starches embedded in the endosperm protein matrix, hence
granule isolation is a more demanding process.

4. • Thus, a counter-current process with water at 50°C for 36-48 h
is required to soften corn (steeping step of processing).
• The steeping water contains 0.2 % S02 in order to loosen the
protein matrix and, thereby, to accelerate the granule release
and increase the starch yield.
• The corn grain is then disintegrated.
• The germ, due to its high oil content, has a low density and is
readily separated by flotation.
• It is the source for corn oil isolation.
• The protein and starch are then separated in hydro cyclones.
• The separation is based on density difference (protein < starch).

5. • The protein by-product is marketed as animal feed or used for
production of a protein hydrolysate (seasoning).
• The recovered starch is washed and dried.
• In the case of wheat flour, a dough is made first, from which a raw
starch suspension is washed out.
• After separation of fiber particles from this suspension, the starch is
fractionated by centrifugation.
• In addition to the relatively pure primary starch, a finer grained
secondary starch is obtained which contains pentosans.
• The starch is then dried and further classified.
• The residue, gluten serves, e.g., as a raw material in the production
of food seasoning and in the isolation of glutamic acid.

6. • If dried gently, it retains its baking quality and is used as a flour improver.
• In the case of rye, the isolation of starch is impeded by the relatively high content of
swelling agents.
• Starch isolated from the tubers of various plants in tropical countries is available on the
market under a variety of names (e.g., canna, maranta, and tacca starch).
• The real sago is the product obtained from the pith of the sago palm.
• Starch is a mixture of two glucans, amylose and amylopectin.
• Most starches contain 20-30% amylose
• New corn cultivars (amylomaize) have been developed which contain 50-80% amylose.
• The amylose can be isolated from starch, e.g., by crystallization of a starch dispersion,
usually in the presence of salts (MgS04) or by precipitation with a polar organic
compound (alcohols, such as n-butanol, or low fatty acids, such as caprylic or capric),
which forms a complex with amylose and thus enhance its precipitation.

7. • Normal starch granules contain 70-80% amylopectin, while some corn cultivars and
millet, denoted as waxy maize or waxy millet, contain almost 100 % amylopectin.
• Structure and Properties of Starch Granules
• Starch granules are formed in the amyloplasts.
• These granules are simple or compound and consist of concentric or eccentric layers of
varying density.
• They are of varying size 2-150 micrometer), size distribution, and shape.
• In addition to amylose and amylopectin, they usually contain small amounts of proteins
and lipids.
• They are examined by using various physical methods, including light microscopy, small-
angle light scattering, electron microscopy, X-ray diffraction, small-angle neutron
scattering, and small-angle Xray scattering.

8. • On the basis of X-ray diffraction experiments, starch granules are said to have a semi
crystalline character, which indicates a high degree of orientation of the glucan molecules.
About 70% of the mass of a starch granule is regarded as amorphous and 30% as crystalline.
• The amorphous regions contain the main amount of amylose, but also a considerable part of
the amylopectin.
• The crystalline regions consist primarily of amylopectin.
• Although this finding was surprising at first because of the branched structure of
amylopectin, it was deduced from the fact that amylose can be dissolved out of the granule
without disturbing the crystalline character and that even amylose- free starches, like waxy
com starch, are semicrystalline.
• The degree of crystallinity depends on the water content.

9. Amylose
• Amylose is a chain polymer of α -D-
glucopyranosyl residues linked 1 ~ 4:

10. Enzymatic hydrolysis of the chain is achieved by (α-amylase, β-amylase and
glucoamylase.
Often, β-amylase does not degrade the molecule completely into maltose,
since a very low branching is found along the chain with α ( 1 6) linkages.
The polymerization degree in wheat starch is 1,000-2,000, while in potatoes it
can rise up to 4,500.

11. Amylopectin
• Amylopectin is a branched glucan
with side chains attached in the 6-
position of the glucose residues of
the principal chain:

12. • An average of 15-30 glucose residues are present in short chain branches and each of these
branch chains is joined by linkage of C-l to C- 6 of the next chain.
• Enzymatic degradation of amylopectin is like that of amylose. The enzyme β-amylase degrades
the molecule up to the branching points.
• The remaining resistant core is designated as "limit-dextrin".
• Amylopectin, when heated in water, forms a transparent, highly viscous solution, which is ropy,
sticky and coherent.
• Unlike with amylose, there is no tendency toward retrogradation.
• There are no staling or aging phenomena and no gelling, except at very high concentrations.
• However, there is a rapid viscosity drop in acidic media and on autoclaving or applying
stronger mechanical shear force.

13. Utilization of
starch
Starch is an important thickening and binding agent and is used extensively in
the production of puddings, soups, sauces, salad dressings, diet food
preparations for infants, pastry filling, mayonnaise, etc.
Starch is an important thickening and binding agent and is used extensively in
the production of puddings, soups, sauces, salad dressings, diet food
preparations for infants, pastry filling, mayonnaise, etc.
Corn starch is the main food starch and an important raw material for the
isolation of starch syrup and glucose.
Corn starch is the main food starch and an important raw material for the
isolation of starch syrup and glucose.
A layer of amylose can be used as a protecting cover for fruits (dates or figs)
and dehydrated and candied fruits, preventing their sticking together.
A layer of amylose can be used as a protecting cover for fruits (dates or figs)
and dehydrated and candied fruits, preventing their sticking together.
Amylose treatment of French fries decreases their susceptibility to oxidation.
Amylose treatment of French fries decreases their susceptibility to oxidation.
The good gelling property of a dispersible amylose makes it a suitable
ingredient in instant puddings or sauces.
The good gelling property of a dispersible amylose makes it a suitable
ingredient in instant puddings or sauces.
Amylose films can be used for food packaging, as edible wrapping or tubing,
as exemplified by a variety of instant coffee or tea products.
Amylose films can be used for food packaging, as edible wrapping or tubing,
as exemplified by a variety of instant coffee or tea products.

14. Starch
gelatinization
• Starch gelatinization is the process where starch and water are subjected to
heat causing the starch granules to swell.
• As a result, the water is gradually absorbed in an irreversible manner.
• This gives the system a viscous and transparent texture.
• The result of the reaction is a gel, which is used in sauces, puddings, creams
and other food products, providing a pleasing texture.

15. • The most common example to explain this phenomenon is pasta
preparation: pasta is made mostly of semolina wheat (wheat flour) that
contains high amounts of starch.
• When it is cooked in boiling water, the size increases because it
absorbs water and it gets a soft texture

16. Starch retrogradation
• Retrogradation is a reaction that takes place when the amylose and amylopectin chains in
cooked, gelatinized starch realign themselves as the cooked starch cools.
• When native starch is heated and dissolved in water, the crystalline structure of amylose and
amylopectin molecules is lost and they hydrate to form a viscous solution.
• If the viscous solution is cooled or left at lower temperature for a long enough period, the linear
molecules, amylose, and linear parts of amylopectin molecules retrograde and rearrange
themselves again to a more crystalline structure.
• The linear chains place themselves parallel and form hydrogen bridges.
• In viscous solutions the viscosity increases to form a gel.
• At temperatures between –8 and +8 °C the aging process is enhanced drastically.
• Amylose crystallization occurs much faster than crystallization of the amylopectin.
•

17. • The crystal melting temperature of amylose is much
higher (about 150 ℃) than amylopectin (about 50-
60 ℃).
• The temperature range between cooking starch and
storing in room temperature is optimum for amylose
crystallization and, therefore amylose crystallization
is responsible for the development of initial
hardness of the starch gel.
• On the other hand, amylopectin has a narrower
temperature range for crystallization since
crystallization does not happen when the
temperature is higher than its melting temperature.
• Therefore, amylopectin is responsible for
development of the long term crystallinity and gel
structure.

18. Pectin
• Generally, it is a group of polysaccharides
found in nature in the primary cell walls of
all seed-bearing plants and are invariably
located in the middle lamella.
• One of the richest sources of pectin is
lemon or orange rind which contains about
30% of this polysaccharide.
• Pectin is naturally found in a number of
plants : lemon peel, orange peel, apple
pomace, carrots, sunflower seed, guava
peel, mango peel and papaya peel.

19. Biological
Sources
Pectin is the purified admixture of
polysaccharides, obtained by carrying
out the hydrolysis in an acidic medium
of the inner part of the rind of citrus
peels.
Citrus limon (or Lemon) and Citrus
aurantium (bitter orange) belonging to
the family Rutaceae, or from apple
family: Rosaceae.

20. Geographical
Source
Lemon and
oranges - India,
Africa and other
tropical countries.
Apple - Himalayas,
California

21. Structure of pectin
• Pectin is structural heteropolysaccharide.
• The main chain consists of α-1,4-linked d-
galacturonic acid.
• Pectin is contained in the primary cell
walls of terrestrial plants.
• For example, citrus peels consist of about
30% pectin.

22. • Pectin, any of a group of water-soluble carbohydrate substances that are found in
the cell walls and intercellular tissues of certain plants.
• In the fruits of plants, pectin helps keep the walls of adjacent cells joined together.
• Immature fruits contain the precursor substance protopectin, which is converted
to pectin and becomes more water-soluble as ripening proceeds.
• At this stage the pectin helps ripening fruits to remain firm and retain their shape.
• As a fruit becomes overripe, the pectin in it is broken down to simple sugars that
are completely water-soluble. As a result, the overripe fruit becomes soft and
begins to lose its shape.
• Because of its ability to form a thick gel-like solution, pectin is used commercially
in the preparation of jellies, jams, and marmalades.

23. • Its thickening properties also make it useful in the confectionery, pharmaceutical, and
textile industries.
• Pectic substances consist of an associated group of polysaccharides that are extractable
with hot water or with aqueous solutions of dilute acids.
• The chief sources of commercial pectin are the peels of citrus fruits, and to a lesser extent
apple pomace (residue from cider presses).
• Very small amounts of pectin suffice in the presence of fruit acids and sugar to form
a jelly.
• Pectin also has several health benefits in humans. Included among these are its ability to
reduce low-density lipoprotein (LDL) levels, thereby lowering cholesterol levels, and its
ability to slow the passage of food through the intestine, relieving diarrhea.
• Pectins can also activate cell death pathways in cancer cells, indicating that pectins may
play an important role in preventing certain types of cancer.

24. Cellulose
• Cellulose is an organic compound with the formula (C6H10O5)n, polysaccharide consisting of a
linear chain of several hundred to many thousands of β(1→4) linked D-glucose units.
• Cellulose is an important structural component of the primary cell wall of green plants, many
forms of algae and the oomycetes (“water molds”). Some species of bacteria secrete it to form
biofilms.
• Cellulose is the most abundant organic polymer on Earth.
• The cellulose content of cotton fiber is 90%, that of wood is 40–50% and that of dried hemp is
approximately 45%.
• Cellulose is mainly used to produce paperboard and paper.
• Smaller quantities are converted into a wide variety of derivative products such as cellophane and
rayon.

25. Cellulose
• Conversion of cellulose from energy crops into biofuels such as cellulosic ethanol is under
investigation as an alternative fuel source.
• Cellulose for industrial use is mainly obtained from wood pulp and cotton.
• Some animals, particularly ruminants and termites, can digest cellulose with the help of
symbiotic micro-organisms that live in their guts, such as Trichonympha.
• In humans, cellulose acts as a hydrophilic bulking agent for feces and is often referred to as a
"dietary fiber".

26. Properties

27. Structure and properties
• Cellulose has no taste, is odorless, is hydrophilic with the contact angle of 20–30, is insoluble
in water and most organic solvents, is chiral and is biodegradable.
• It can be broken down chemically into its glucose units by treating it with concentrated acids
at high temperature.
• Cellulose is derived from D-glucose units, which condense through β(1→4)-glycosidic bonds.
• This linkage motif contrasts with that for α(1→4)-glycosidic bonds present in starch,
glycogen, and other carbohydrates.

28. • Cellulose is a straight chain polymer: unlike starch, no coiling or branching occurs, and
the molecule adopts an extended and rather stiff rod-like conformation, aided by the
equatorial conformation of the glucose residues.
• The multiple hydroxyl groups on the glucose from one chain form hydrogen bonds with
oxygen atoms on the same or on a neighbor chain, holding the chains firmly together
side-by-side and forming microfibrils with high tensile strength.
• This confers tensile strength in cell walls, where cellulose microfibrils are meshed into a
polysaccharide matrix.

29. Application
• Paper products: Cellulose is the major constituent of paper, paperboard, and card stock
• Fibers: Cellulose is the main ingredient of textiles made from cotton, linen, and other plant fibers.
It can be turned into rayon, an important fiber that has been used for textiles since the beginning of
the 20th century. Both cellophane and rayon are known as "regenerated cellulose fibers"; they are
identical to cellulose in chemical structure and are usually made from dissolving pulp via viscose.
A more recent and environmentally friendly method to produce a form of rayon is the Lyocell
process.

30. Application
• Consumables: Microcrystalline cellulose (E460i) and powdered cellulose (E460ii) are used as
inactive fillers in drug tablets and as thickeners and stabilizers in processed foods. Cellulose
powder is, for example, used in Kraft's Parmesan cheese to prevent caking inside-of the package.
• Science: Cellulose is used in the laboratory as a stationary phase for thin layer chromatography.
Cellulose fibers are also used in liquid filtration, sometimes in combination with diatomaceous
earth or other filtration media, to create a filter bed of inert material