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108 Textbook of Pharmacognosy
Culinary Uses
Starch is widely used in the form of prepared foods such as bread, pan
cakes, cereals, noodles, pasta, porridge, etc. Commercial refined starches
like corn starch, tapioca, and wheat and potato starch are used in industry.
Because of its absorbent properties, starch is an important ingredient of all
talcum powders. Starch is also the starting material for the commercial
manufacture of liquid glucose, dextrose and dextrin. Starch is used as a
thickener and a stabiliser in the preparation of puddings, custards, soups,
sauces, gravies, pie fillings, salad dressings, noodles and pastas. It is also
used as a mold in the preparation of jelly beans and wine gums.
Non-medical Uses
The starch is used in paper manufacturing to increase the strength of the
paper and also in surface sizing of the paper and also as a binder for coating
the pigments to improve smoothness, hardness, whiteness and gloss. It is
used in the preparation of corrugated paper board, paper bags, confections,
adhesives and wall boards. Starch is used in the manufacture of different
types of glues used for book binding, wall paper adhesives, paper sacks,
gummed paper, envelope adhesives, school glues, gummed tape, etc. It is
also used in the production of laundry starch (clothing starch), in printing
industry, in the production of bioplastics (biodegradable polylactic acid),
body powder (beauty products) in the preparation of drilling fluids (oil
extraction), biofuel (ethanol) and production of hydrogen.
Other Uses of Different types of Cereals
1. Rice: Rice is the most important cereal which forms the basis of the
diet of millions of people in South-East Aisa. About 90% is eaten as
cooked preparations as plain boiled rice in addition to being mixed
with pulses, curd, vegetables, fish or meat. Indian preparations of rice
include kheer and pulao. In South India, fermented preparations like
dosa, idli and uppma are prepared from a mixture of rice and blackgram
after fermentation for 8 to 12 hours and toasted in a pan or cooked in
steam. Rice flour is used in confectionery, ice creams, puddings and
pastry. Rice starch is used industrially in cosmetics, as a thickener in
calico printing, in finishing the textiles, for making the dextrins,
glucose and adhesives. It is used in the preparation of fermented
drinks like ‘sake’ in Japan and ‘wang-tsin’ in China. Hull is used as a
fuel, as bedding for poultry, for packing and insulation. Hull is used
also as filler in concrete and bricks, as a source of sodium silicate in
making soaps, polishes and cleaning agents. Rice bran oil is edible.
The straw is used as a cattle feed, soil mulch, a fertiliser and for
making straw boards. The rice straw is also used for the manufacture
of a very fine paper in China and Japan. It is also used for thatching,
making hats, mats, sacks, ropes and baskets.
Systematic Pharmacognostic Study of Carbohydrates and Derived Products 109
2. Wheat: Wheat is consumed all over the world in various forms. In
advanced countries, it is consumed in the form of leavened bread,
but, in India, 85–90% of it is used in the form of chapathies, and
other culinary preparations like tandoori roti, nan, paratha and
poori. The soft wheat flour is used for making the cakes, biscuits,
pastries, crackers, etc. The hard wheats provide excellent flour for
bread making. Durum wheat is preferred for the manufacture of
macaroni, spaghetti, vermicelli and other products such as noodles.
Smaller amounts are converted into breakfast food like wheat
flakes, puffed wheat and shredded wheat. Industrial uses include
the manufacture of starch, gluten, distilled spirits, malts, pasta, etc.
The starch is used for finishing clothes in the laundries while
gluten is used in the production of monosodium glutamate for
flavouring the food. Wheat bran rich in proteins and vitamins is
used as a livestock feed. Wheat straw is used as a livestock feed,
for animal bedding and for the production of the compost. The
straw is also used in making the corrugated paper and high
qualilty insulated building board. Paste made of wheat starch is
used as an adhesive for paper mending along with Japanese tissue
paper. It is also used in mending flat paper and book hinges. Wheat
flour is one of the most important foods in European and North
American culture and is an ingredient of breads and pastries. Atta
flour is whole-grain wheat flour and is important in Indian and
Pakistani cuisine used for a range of foods like roti, naan and
chapathi. White wheat flour is the traditional base for wall paper
paste and also for papier–mache.
3. Potato: At present, potato occupies a prominent position in the food
economy of the world. As a vegetable, potato is consumed boiled,
steamed, fried, baked or roasted. The processed products of potato
include chips, crisps, dehydrated and mashed potatoes, potato flour
and canned potatoes. A dehydrated potato product, ‘chuno’ is a valued
food by the Andean people. Potato is a good substrate for the growth
of the microorganisms. The potato broth has long been used as a
nutrient medium in microbiology. Potato can also be processed into
many commercial products like starch, alcohol, glucose, lactic acid,
etc. The starch is used for sizing the cloth and paper, in the laundry
industry, and in food preparations. ‘Vodka’, the Russian alcoholic
beverage is prepared by the fermentation of cooked potatoes. Potato
starch is often a substitute thickener for corn starch in cooking and is
considered to be superior for foods that require high temperatures as
it is gluten free. In food, it is used to prepare thick gravy or soups or
stews instead of wheat or corn flour. The potato starch and its
derivatives are used in many recipes like noodles, wine gums, cocktail
nuts, chips, sausages, bakery cream, instant soups and sauces, etc. It
110 Textbook of Pharmacognosy
is also used as wall paper glue, for finishing and sizing the textiles, and
as an adhesive for paper sacks.
4. Maize or corn: Maize is used as a staple human food, a livestock feed
and also as a raw material for many industrial products. Maize was
the main food source of ancient civilisations of the Western
Hemisphere like the Aztecs, Mayas and Incas. In Mexico, boiled maize
is crushed and made into a flat cake called the ‘tortilla’. Corn meal and
corn flakes are the products for consumption by the humans. Corn oil
is used in cooking. Corn starch is a universal foodstuff. Corn syrup
and corn sugar are used in the confectionery, jams and jellies. Maize
is the cheapest and most palatable feed for pigs, cattle, sheep and
poultry. Corn starch is a substitute for talc in bath powder and as a
starching material for clothes. It is also used in the manufacture of
asbestos ceramics, dyes, plastics, oil cloth and linoleum. Corn syrup
is used in shoe polish, glass paper, rayon and tobacco industry. Corn
sugar is used in the preparation of chemicals, leather preparation,
dyes and explosives. Furfural, a compound obtained from maize after
being cooked under pressure with acids, is used in the production of
nylon, in refining diesel, vegetable and lubricating oils, in refining
butadiene and in the production of plastics. Zein, a protein from
maize, is spun into a soft, durable artificial fibre. This is also used as a
foaming agent in fire extinguishers, in the production of linoleum and
oil cloth, a sizing material in textiles and as a binding material for cork
manufacture and to bind paper, glass, wood, etc. Upon fermentation
and distillation, maize produces ethyl alcohol, butyl alcohol, propyl
alcohol, acetaldehyde, acetone, glycerol, acetic acid, citric acid and
lactic acid. ‘Chicha’ is the most common and one of the cheapest
beverages of Peru and Bolivia prepared from maize. Corn oil is used
in the preparation of soaps, varnishes, paints, etc. The cobs are used
for the production of pipes, chemicals, and plastics and also used as
livestock feed. The leaves are used as cigarette wrapper. The husks
from the cobs are used for making mats, hats and mattresses. The
stalks and leaves are sometimes used for production of paper, paperboard and wallboard. The maize cobs which have been pulverised are
used extensively as a mild abrasive for the removal of carbon from
aeroplane mirrors. Maize flour has been important in Mesoamerican
cuisine since ancient times and remains a staple food in Latin
American cuisine. Corn (maize) flour is popular in the Southern and
South Weestern US, Mexico, South America and Punjab region of
India and Pakistan. Corn starch is the refined form of corn flour. Corn
starch is used as an anti-caking agent in confectionery. This is also
used in the manufacture of environmental friendly products like a
biodegradable blue ray compact disc (CD) from Pioneer Company of
Japan (2004). It is also used in the production of powders, skin
Systematic Pharmacognostic Study of Carbohydrates and Derived Products 111
cleansing milk, deodorants, etc. The starch is a nutrient and a
demulcent. Pharmaceutically, it is used as a base for dusting powder
for uncoated pills. It is also used as an antidote for iodine and bromine
poisoning.
Plant Starch vs Animal Starch
The animal starch is not a starch per se, it refers to the constituent of the
animal’s glycogen owing to the similarity in structure and composition of
amylopectin. While the plants store their excess glucose in the form of
starch, the animals do so in the form of glycogen. Glycogen is a branched
polymer of glucose that is mainly produced in the liver and muscles cells
that functions as secondary long-term energy storage the animal cells.
Glycogen is also a complex carbohydrate that primarily serves as a storage
carbohydrate similar to starch. The main difference between the
amylopectin in plants and amylopectin in animals is that the latter has
more extensive branching at every 8–12 glucose units.
GUAR GUM
Synonyms
Guar flour, Jaguar gum, Guaran, Guarkernmehl (German), Gomme de
Guar, Gomme de Jaguar, Farine de guar (French), Goma Guar, Guaro Dervo
(Spanish), Indian Cluster bean.
Biological Source
Guar gum is the powdered endosperm of seeds of Cyamopsis tetragonaloba
(L.) Taub. (= C. psoralioides DC.) (Family: Leguminosae–Fabaceae).
Geographical Source
The plant is probably indigenous to India although it has never been
observed in a wild state. It is being grown from hundreds of years in India
and Pakistan as a fodder, green manure and vegetable and was introduced
into USA in 1900. Now, it is cultivated exclusively in India, Pakistan,
Australia, Indonesia, Burma and parts of Central Africa. Quite recently,
the cultivation has been undertaken in the arid South-Western United
States. In India, two cultivars are recognised, the giant and the dwarf. The
plant is commercially cultivated in Gujarat, Punjab, Haryana, Rajasthan,
Madhya Pradesh, Tamil Nadu, Maharashtra, Karnataka, Andhra Pradesh
and Uttar Pradesh. India and Pakistan are producers of guar seed and
guar gum and around 85% guar is produced in India. The major part is
consumed by oil and natural gas industry and after that major part goes to
food processing industry. India exports guar gum to 145 countries in the
world.
112 Textbook of Pharmacognosy
Cyamopsis tetragonaloba
Mature fruits of guar
Dry fruits and seeds of guar Guar gum
Food grade gum powder Food grade gum
Systematic Pharmacognostic Study of Carbohydrates and Derived Products 113
Collection and Preparation
The guar seeds are mechanically dehusked, hydrated, milled and screened
according to the application, and it is generally produced as a free-flowing,
off-white powder. Guar gum is industrially prepared from well-developed
seeds. The seeds are put into a grinder to bifurcate guar seeds. The seeds
are separated into husk and embryo. The husk contains fibrous matter
and the gum is located in the endosperm. Guar seeds contain 14–17% of
hull, 38–45% of endosperm and 45–50% of germ. Cotyledons are separated
from the endosperm by winnowing. The endosperm, i.e. crude guar gum,
is pulverised by means of micropulveriser and grinding for 15 minutes.
The endosperm being harder is not affected by micropulveriser. Finally, it
is sifted through sieves of 4 to 60 mesh to give granular and powdered
gum.
Characters
Guar gum is colourless or pale yellowish-white coloured, coarse to finely
ground powder, practically odourless with a bland taste. Guar gum
disperses and swells rapidly in hot or cold water with a translucent
suspension. 0.5% aqueous solution of gum is neutral to litmus. It is insoluble
in organic solvents. The viscosity depends on temperature, pH, particle
size, etc.
Chemical Constituents
The principal constituent of the gum is a galactomannan (guar gum) or
mannogalacton, a complex polysaccharide which consists of 34.5% of
D-galactose and 65.4% of D-mannose and readily forms a viscous gel with
water. Fatty acids, both free and as esters, have been reported by GLC-NS
analysis. The gum is more soluble in water and is a better emulsifier. In
water, it is non-ionic and hydro-colloidal. It remains stable in solution over
Guaran—the repeating unit in Guar gum
114 Textbook of Pharmacognosy
D-galactose (C6H12O6)
D-mannose (C6H12O6)
a pH range of 5.0–11.0 but degrades at a pH of 3.0 at 50°C. Strong acids
cause hydrolysis and loss of viscosity of the gum. It is insoluble in most of
the hydrocarbon solvents.
History of Guar
Guar is a native to the Indian subcontinent and is grown mainly in India,
Pakistan, and USA and also in some parts of Africa and Australia. In old
times, it was only used as a rich protein food for cattle (the beans and the
stems) and also as a green vegetable in India. The plant has been cultivated
in India since centuries and India accounts for 80% of the total guar
produced in the world. Historically, it has been an important source of
nutrition for humans as well as animals. Just after the Second World War,
there was a severe locust bean gum shortage which adversely affected the
paper and textile industries and guar gum was found to be the most suitable
substitute. It was introduced into America in 1903 and the technology of
extraction of the gum was commercialised in USA in 1953 and a decade
later in India (1960s). In India, when the farmers realised its drought
tolerance, they grew it as a forage crop for cattle, which resulted in its
name as guar meaning ‘cattle fodder’. The gum has been used for centuries
as a thickening agent for foods and pharmaceuticals and it continues in
paper, textile and oil drilling industries.
Medicinal Uses
Guar gum has recently received some attention as a possible oral
hypoglycaemic drug. It can produce changes in gastric emptying and
in the gastrointestinal transition time, which can delay absorption of
sugars and oligosaccharides from the gut. It is used as a binder or a
disintegrator in the preparation of tablets pharmaceutically. It is useful
as a bulk laxative as it promotes regular bowel movement, relieves
constipation, colitis and irritable bowel syndrome. It is also used to treat
obesity, diabetes and for preventing atherosclerosis (hardening of the
arteries). Following ingestion, it speeds up the removal of the waste
and bacteria from colon and also helps absorption of toxic substances
and bacteria during infective diarrhoea. Many studies indicated that
the gum ingestion decreases significantly, the cholesterol levels in the
Systematic Pharmacognostic Study of Carbohydrates and Derived Products 115
human serum which may be due to its high soluble fibre content. It
also helps as an adjuvant for the diabetic drugs used for the treatment
of non-insulin dependent diabetes.
Non-medical Uses
a. Culinary and dietary uses: The young tender pods are used as a
vegetable and the mature dry seeds as a valuable cattle feed. It is also
used as a forage crop and a green manure in India, Pakistan,
Indonesia and Eastern countries. The flour is chiefly used as a
stabiliser and a thickener in the production of the food products, for
sizing the textiles and products of paper. It is also used as an
emulsifier in salad dressings, as a flocculent in mining industry in
addition to the manufacture of cosmetics. The flour forms excellent
films as such it is used for backing the postage stamps. The drought–
resistant bean is eaten, fed to cattle and used as a green manure. It is
used to increase the dough yield, to give greater resiliency and
improve the texture and shelf-life of bakery goods. It is useful in
dairy industry as it helps thickening the milk, yoghurt, chewing
gums and liquid cheese products, sauces, ketchups, etc. It is used in
the preparation of dry soups, sweet desserts, and canned fish in
sauce and frozen food items. It is used to stabilise the ice creams in a
short time and to slow down the melting of the ice creams. It acts as
a lubricant and prevents loss of weight during storage by binding the
moisture in meat products. It is used in cosmetics as it thickens the
creams and lotions. In foods and beverages the gum is used as a
thickening agent, a stabilising agent, as a suspending agent and a
binding agent.
b. Industrial uses: The guar gum is used in various industries because
of its ability to suspend the solids, to bind water by hydrogen
bonding, to control the viscosity of the aqueous solutions and to form
strong and tough films. It has many industrial applications in paper,
textile and oil drilling, mining, explosives and ore floatation.
Industrially, the gum is used as a controlling agent in oil wells to
facilitate easy drilling and prevent fluid loss, as an emulsifier because
it helps to prevent oil droplets from coalescing and also as a stabiliser
as it helps to prevent solid particles from settling. It is used primarily
as a proppant transport/proppant suspending agent in hydraulic
fracturing (in shale oil and gas extraction industries). In textile
industry, it is used in sizing, finishing and printing. It is used to
improve sheet formation, folding and denser surface for printing in
paper industry. It is useful as a waterproofing agent mixed with
ammonium nitrate and nitroglycerine in explosives industry. It can be
used as a thickener in toothpastes, as a conditioner in shampoos in
cosmetic and toiletry industry.
116 Textbook of Pharmacognosy
Side Effects
The side effects of consuming guar gum by mouth include increased gas
production, diarrhoea and loose stools. These effects usually decrease or
disappear after several days of use. Higher doses of guar gum or not
drinking enough fluid (water) along with the dose of gum can cause choking
or blockage of the oesophagus and the intestines.
PECTIN
Synonyms
Acide pectinique, Acide pectique, Apple pectin, Citrus pectin, Fractionated
pectin, Fruit pectin, Grapefruit pectin, lemon pectin, Pectinic acid, Pectina,
Pectine d’Agrume, Pectine de Pomme.
Pectin is derived from Greek, Pektikos meaning ‘congealed’ or ‘curdled’
and is a structural heteropolysaccharide in the primay cell walls of
terrestrial plants. It was first isolated and described by Henry Braconnot
(1825).
Biological Source
Commerically pectin is produced as a white to light brown powder mainly
from citrus fruits. Pectin is the purified carbohydrate product obtained by
acid hydrolysis from the inner portion of the rind of Citrus peels, i.e. Citrus
limon, Citrus aurantium (Family: Rutaceae) and the remains of apples after
squeezing for juice. Other fruits like apricots, plums, carrots, gooseberries
(with much pectin), cherries, grapes, strawberries papaya, guava and
mangoes (with less pectin) are also the source of pectin.
Geographical Source
USA, Switzerland and other European countries are producing pectin either
from citrus peels or from apple pomace.
Collection and Preparation
The main sources of pectin are pears, apples, guavas, quince, plums,
gooseberries and other citrus fruits which contain large amounts of pectin.
The soft fruits such as cherries, grapes, and strawberries contain the small
amounts. The main raw material for pectin production is the dried peels of
citrus or apple pomace, both byproducts of juice production. Pomace from
sugar beets is also used to a small extent.
The preserved or fresh peels of citrus are heated with 20 times its weight
of water at 90°C for 30 minutes in presence of hot dilute acid (citric acid,
lactic acid or tartaric acid) maintaining the pH between 1.5 and 3.5. During
the process of extraction, the protopectin loses some of its branching and
chain length, and goes into solution. The aqueous extract thus obtained is
Systematic Pharmacognostic Study of Carbohydrates and Derived Products 117
filtered and the filtrate is concentrated in a vacuum and the pectin is
precipitated by the addition of ethanol or isopropanol (alcohol). The
precipitated pectin is separated, washed and dried. Following drying and
milling, pectin is usually standardised with sugar and sometimes calcium
salts or organic acids to have an optimum performance in its application.
Pectin is incompatible with calcium, so necessary precaution should be
taken to keep it away from its metallic salts throughout the process of
extraction.
Characters
Pectin is white to cream coloured, odourless, amorphous, mucilaginous,
coarse or fine powder. It is completely soluble in 20 parts of water and the
solution is viscous, colloidal and acidic to litmus. Pectin forms a stiff jelly
if it is heated with 9 parts of water. It is insoluble in alcohol and other
organic solvents. Pectin is more stable in acid media than in alkaline media.
It occurs in ripe fruits and certain vegetables. Protopectin, the precursor,
present in unripe fruits gets converted to pectin as the fruits ripen. In overripe fruits the pectin becomes pectic acid. In plant cells, pectin consists of a
complex set of polysaccharides present in most primary cell walls and
abundant in the non-woody parts of terrestrial plants. This is present
throughout the primary cell wall but also in the middle lamella between
the plant cells where it helps to bind the cells together. The amount,
structure and chemical composition of the pectin differs from plant to plant
and within a plant overtime and in different parts of the plant.
Liquid pectin
Pectin powder
Forms of Pectin
The different types of pectin behaving differently are: Dry pectin—which
comes in multiple forms, tailored to the amount of sugar in a recipe; Liquid
pectin—which is similar to dry pectin but pre-dissolved to avoid clumping;
HM (high methoxyl) pectin—that comes in fast-set and low-set varieties; Fast