Transcript LEGUMES

LEGUMES
Legume Family - Fabaceae
All types of beans and peas
 Soybean, peanut, alfalfa, clover
 Also includes various trees such as
black locust, redbud
 One of the largest dicot families 13,000 species
 Ranks right behind grasses in human
impact
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Family characteristics
Five-petalled irregular flower with
bilateral symmetry
 Fruit is a legume (dry dehiscent fruit two lines of dehiscence) with one row of
seeds
 Seeds contain two large cotyledons
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Legume flower
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Irregular flower with
bilateral symmetry
Often butterflyshaped
Legume seeds
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Important food
staple worldwide
Rich in both oil and
protein
» Higher in protein than
any other food plants
» Close to animal meat
in protein quality
» Often called "poor
man's meat"
Legumes and
nitrogen-fixing bacteria
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High protein correlated with root nodules
which contain nitrogen-fixing bacteria
» convert atmospheric nitrogen to useful form
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Because of this legumes enrich the soil
» Farmers often rotate legumes with crops
that deplete soil nitrogen (soybean & corn)
» "Green manure" crops plowed sometimes
» Reduces need for fertilizers - legumes can
be cultivated worldwide - even in poor soils
Nitrogen cycle
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Nitrogen
» essential elements for all living organisms
» major component of amino acids, proteins,
nucleic acids
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Nitrogen gas (N2) about 79% of the air
» most living organisms cannot use this form
of nitrogen
Nitrogen-fixing bacteria
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Certain bacteria and cyanobacteria have
ability to reduce nitrogen (N2) gas to
ammonium NH4+
» cells can convert NH4+ to compounds
» called nitrogen-fixation
» organisms are called nitrogen-fixing
Nitrogen-fixing organisms
Some bacteria and some cyanobacteria
 Some live freely in the soil
 Most are found in symbiotic associations
in the root nodules of legumes
 Azolla is known to have a symbiotic
association with a nitrogen-fixing
cyanobacterium
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Non-legume plants
Must rely on the nitrogen compounds
present in the soil
 During decomposition microorganisms
break down proteins and other nitrogencontaining molecules into ammonium
NH4+
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Nitrogen compounds in soil
Some plants take up ammonium directly
 Bacteria in the soil quickly convert
ammonium to nitrite (NO2) and then
nitrate - (NO3)
 Nitrate is the form of nitrogen usually
absorbed by plants
 Fertilizer contain a mixture of both
ammonium and nitrate
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Nitrogen Cycle
Non-legume
plants
bacteria
NO3
NH4
bacteria
NO2
bacteria
Other sources of nitrogen
Burning fossil fuels, volcanic activity,
and lightning combine nitrogen and
oxygen into NO2 and NO3
 These are washed into the soil by rain
and contribute to the nitrogen cycle
 Denitrifying bacteria actually break down
ammonium and nitrates returning
nitrogen gas to the atmosphere
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Legume food crops
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Cultivated for thousands of years in both
the Old World and New World
» seeds easily harvested
» seeds low water content and easily stored
for long periods of time
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These features plus their high protein
content and ease in growing make them
ideal crops
Beans and peas -- Pulses
Some of the oldest and most common
food crops
 Good source of protein average about
25% for beans and 21% for peas
 Traditionally cultivated for dry seeds
 Some varieties today have edible pods
 Beans warm season annuals
 Peas grown during the cooler seasons
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Common Edible Beans & Peas
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Black-eyed peas
Butter beans
Chick peas
Fava (broad) beans
Green beans
Green peas
Kidney bean
Lentils
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Lima beans
Mung beans
Navy bean
Pinto beans
Snow peas
Split peas
Wax bean
Peanuts
Also called goobers and groundnuts
 Native to South America
 Time of domestication is unknown
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» gold and silver peanut-shaped jewelry
dicovered in Peru in the tomb of a Moche
warrior priest
» peanut played a prominent role in the
ancient Moche civilization
» Carbon dating of tomb - 290 A.D.
Sixteenth century
Spanish explorers discovered peanuts
in South America and took to Europe
 Trading introduced peanuts to Africa
where it became widely cultivated
 The slave trade brought the peanut to
North America
 Today a staple crop in the south grown
in Georgia, North Carolina, Texas,
Alabama, Oklahoma and Virginia
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Peanut - Arachis hypogea
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Unusual plant
After pollination the
flower stalk grows
downward pushing
the developing fruit
into the soil
Fruit matures
underground typically with two
seeds (peanuts)
Nutrition
Highly nutritious with 45-50% oil and 2530% protein
 Over one billion pounds per year
consumed in the US
 Mainly as a snack food, in candy, and in
peanut butter
 Half the U.S. crop is used to make
peanut butter
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Peanut butter
First developed by a St. Louis physician
in the 1890's as a nutritious and easily
digested food for invalids who had
difficulty chewing
 Consume enough peanut butter each
year to “fill the Grand Canyon”
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Peanut oil
Found in margarine, shortening, salad
dressing, and cooking oil
 Soaps, cosmetics, and shaving cream
 Industrial products such as plastics and
paints
 Pressed cake that remains after the
extraction of oil is used as a high protein
livestock feed
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Versatility of the peanut
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George Washington Carver (1864-1943)
» Developed over 300 food and industrial
uses for the peanut
» Encouraged its cultivation in the South
» Revitalized Southern agriculture exhausted
by years of cotton cultivation
» Also introduced other soil-enriching
legumes like soybean
Soybean - Glycine max
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Relatively new to the
West but used in the
Orient for centuries
It was considered
one of the sacred
crops of the ancient
Chinese
Domesticated in
northern China at
least 3000 years ago
History in North America
Introduced in late 18th or early 19th
century
 Little interest until the 1920's
 Today U.S. - world's leading producer
 Often called the "Cinderella crop"
 Reasons: versatility of the soybean and
its suitability for growing in the corn belt
region
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Nutritional value of soybeans
One of the richest foods with 13-25% oil
and 30-50% protein
 Higher protein content than beef
 Although originally used solely as animal
feed, the soy protein is used more and
more in the human diet
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Food use of soybean
Since ancient times in Asia, soybeans
have been consumed in hundreds of
different ways
 Not edible raw
 Cooked they can be eaten whole
 Often made into a paste, curd, or "milk"
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Soy Products
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Soy sauce
» Traditionally made by fermenting soybeans
in brine but today some synthetic
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Soy milk
» Beans soaked in water and pureed
» Mixture is heated and the liquid poured off
as soy milk
» Non-dairy substitute for milk and baby
formula (for lactose intolerant) individuals
Tofu
Made from the curds of soy milk
 Extremely versatile and used in main
dishes in Japanese and Chinese meals
 Made into cheeses, sour cream, and
other imitation dairy products
 Ice cream-like desert - Tofutti
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Soy flour
After the extraction of oil, the meal that
remains can be made into flour
 Can be mixed with wheat flour in a
variety of bread, pasta, baked goods,
and breakfast foods
 Replacing just a small fraction of the
wheat flour with soy flour significantly
improves the protein content
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Other soybean foods
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Miso - (from Japan) prepared from soybeans,
salt, and rice; fermented by fungi for a several
months and then ground into a paste and
used as a spread, in soups, etc
Tempeh- (from Indonesia) fermented soybean
cakes made by inoculating parboiled
soybeans with a fungus and allowing it to
grow for a few days. The fungal mycelium
binds the soybeans together into a cake which
can be sliced and cooked in various ways
More Soy Products
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Textured vegetable protein
» Produced by spinning the soy protein into long
slender fibers
» Picks up flavors from other substances
» Made into imitation meats and used as meat
extenders
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Lecithin - common food additive
» Lipid extracted from soybeans
» Stabilizes and extends the shelf life
» Added to packaged foods - cake mixes, instant
beverages, whipped toppings, and salad dressings
Soybean oil
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Food uses
» Cooking oil, salad oil, margarine, shortening, and
prepared salad dressings
» Americans consume almost 6 gallons per year
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Industrial uses
» Paints, inks, soaps, cosmetics, biodiesel fuel
» Soybean-based "plastic" car body built by Henry
Ford in 1940
– Ford's commitment to the soybean was so great
that at one point he stated his goal was to "grow
cars rather than mine them"
Other legumes of interest
Forage plants - alfalfa and clover
 Super tree - Leucaena leucocephala
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» tropical tree that is one of the fastest
growing species of woody plants for fire
wood, wood pulp, and enriching the soil
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Beans of the future:
» Winged bean - all parts of plant are edible pod, seeds, leaves, flowers, root
» Tepary bean - adapted to arid tropical areas
Summary
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Legumes are second only to the cereals in
their importance in human nutrition and are an
excellent source of high quality protein
Nitrogen fixation is important for generating
nitrogen compounds that can be used by
plants
Soybean has been transformed into a variety
of food products and is increasing its role in
the human diet