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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. Family characteristics. - PowerPoint PPT Presentation
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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
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
Legume flower
Irregular flower with bilateral symmetry
Often butterfly-shaped
Legume seeds
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
High protein correlated with root nodules which contain nitrogen-fixing bacteria» convert atmospheric nitrogen to useful form
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
Nitrogen » essential elements for all living organisms» major component of amino acids, proteins,
nucleic acids
Nitrogen gas (N2) about 79% of the air
» most living organisms cannot use this form of nitrogen
Nitrogen-fixing bacteria
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
Non-legume plants
Must rely on the nitrogen compounds present in the soil
During decomposition microorganisms break down proteins and other nitrogen-containing molecules into ammonium NH4
+
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
Nitrogen Cycle
NH4
NO2
NO3
bacteria
bacteria bacteria
Non-legumeplants
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
Legume food crops
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 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
Common Edible Beans & Peas
Black-eyed peas Butter beans Chick peas Fava (broad) beans Green beans Green peas Kidney bean Lentils
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
» 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
Peanut - Arachis hypogea
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 25-30% 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
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”
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
Versatility of the peanut
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
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
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
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"
Soy Products
Soy sauce» Traditionally made by fermenting soybeans in
brine but today some synthetic 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
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
Other soybean foods
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
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
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 Food uses
» Cooking oil, salad oil, margarine, shortening, and prepared salad dressings
» Americans consume almost 6 gallons per year
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
» tropical tree that is one of the fastest growing species of woody plants for fire wood, wood pulp, and enriching the soil
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
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