Starchy Staples

Starchy Staples

Most plants store food reserves in the form of starch

Often these reserves are stored in underground organs

Some types of roots or modified stems

Starchy Staples Potato, sweet potato

and cassava among top ten crops

All are tropical in origin but grown extensively in temperate areas today

Starchy Staples All propagated asexually Highly productive > many tons per acre Food insurance against some disasters such as

fire, typhoons, or hail High in carbohydrates, mostly starch, but low

in protein and fat

Modified stems Variety of functions.

– some specialized for asexual reproduction– some specialized for food storage– some for both

Available for renewed growth upon the return of favorable weather conditions

Modified stems, like erect stems, have recognizable nodes and internodes.

Stolons or runners Above ground horizontal stems that

produce buds and roots at the nodes These buds develop into new plantlets Area can be quickly invaded through this

method of vegetative reproduction

Rhizomes Underground horizontal stems Roots form all along the underside Buds found at nodes can give rise to new

plants Rhizome may also be a food storage organ

Tubers Enlarged storage tips of a rhizome White potato is a tuber "Eyes" of the potato are actually buds

located at the nodes, and each bud can give rise to a new plant

Bulbs and corms Modified stems found in monocots Bulbs are erect underground stems with both

fleshy and papery leaves - food is stored in the fleshy leaves -- onions

Bulbs themselves can multiply Corms store food reserves in the stem --no

fleshy leaves -- taro Corms can multiply

Storage roots Tuberous roots modified fibrous roots that

become fleshy and enlarged with food reserves -- sweet potato– can also function in asexual reproduction

Tap roots are food storing organs for biennial plants such as carrots, rutabagas, and turnips

WHITE POTATO Solanum tuberosum Member of the family

Solanaceae, Nightshade Family

Other members are tomato, eggplant, pepper, nightshade, and other poisonous plants

South American origins Archeological evidence shows that 8000 years

ago indigenous people living in the Andes Mts. collected wild potatoes (in what is now Peru)

At some point the potato became the staple food crop for the people in this area

When the Spanish conquered Peru in the 1530's, the potato was the staple of the Inca civilization spread over thousands of miles

Introduction to Europe

Potato introduced to Spain sometime during the middle to late 16th century

Potato cultivation slowly spread throughout Europe - only accepted as a food for humans in the 18th century

Lots of misinformation - Other members of the family known to be poisonous or hallucinogenic

Tuber is the only part safe to eat; all the above ground parts are poisonous

Potato in Ireland Readily accepted in Ireland Established crop as early as 1625 Dietary staple for the Irish peasant

throughout the 18th and the first half of the 19th century

Climate and soil ideal for the potato Even small plot could feed a family

Ireland Potato was so successful that it led to

population increase - from 1.5 million to 8.5 million between 1760 and 1840

The poor subsisted on potatoes, some milk, and only occasionally fish or meat

Estimates - average adult consumed between 8 to 12 pounds of potatoes each day

Phytophthora infestans Fungus causes the disease late blight of potato Fungus attacks and destroys the leaves and

stem causing them to blacken and decay in a short time and stopping tuber growth

Tubers are also attacked and rot in the ground or even later in storage

In cool wet weather, the fungus can kill a plant within a week.

Late blight disease in Europe First appeared in Europe in 1844 Accidentally carried with new varieties of

potato from Central or South America First appeared in Ireland in August of 1845

Irish potato famine Disease struck several times during the period of

1845 to 1849 Widespread destruction of the potato crop led to

devastating famines among the Irish Over one million died from starvation or from

diseases that followed the famine 1.5 million Irish emigrated to other area-

especially the United States, resulting in a 25-30% decline of the population

Potato in rest of Europe Widely grown in Europe because it was

encouraged by the aristocracy as a cheap food for the peasants

By the end of 18th century potato gained widespread acceptance throughout Europe

Potato blight devastated the crops in Europe but effects were not as severe as the Irish famine since the potato was not the sole dietary staple

Potato in the United States Potato made its appearance in North America

through the European colonies There is some doubt as to the exact date of

introduction 1621? or 1719? Confusion in historical records between the white

potato and the sweet potato Word potato stems from the Arawak Indian word

batata which actually referred to the sweet potato

United States today U.S. production about 5% of the world total Potatoes grown in virtually every state Top producing states are Idaho, Washington,

and Maine One-third of U.S. harvest consumed fresh One-half is processed to make frozen French

fries, potato chips, dehydrated flakes, and other products including potato starch.

Processed potatoes Nothing new - Peruvian people from high in Andes

Mts have made chuno, a freeze-dried dehydrated potato, for about 2000 years

Tubers are spread on the ground when a heavy frost is expected

Following freezing, the potatoes thaw during the day and are trampled to get rid of water - repeated until completely dried

Chuno can be stored for several years without spoiling

Solanum tuberosum Solanum, a large genus with over 2000

species Member of the Solanaceae or nightshade

family Almost 6000 cultivars but most commercial

growers plant a limited number of varieties In the U.S, 12 account for 85% of the potato

harvest

The potato plant Bushy herbaceous annual with an alternate

arrangement of large pinnately compound leaves - does best in cool climates

Two types of stems are produced– ordinary stems with leaves– underground rhizomes which end in tubers

Anatomically, the tuber is a modified version of a dicot stem

Potato cultivation Propagated by "seed potatoes" - small

pieces with at least one eye Produces plants genetically identical to the

parent and maintains the desired traits within a cultivar

Seed potatoes produced by farmers who specialize in growing only seed potatoes

Asexual reproduction Advantages - faster and produces plants with

desired qualities Disadvantages - genetically identical plants

share the same susceptibility to adverse environmental conditions and diseases– Most of the potatoes in Ireland were genetically

identical - derived from one or two plants introduced into the country

– A monoculture is always risky

Four familiar cultivars Round white is an all purpose potato good for

boiling, baking, or processing into chips, fries, or flakes

Russets (Idahos) elongate cylindrical tubers have a corky russet-colored skin and mealy texture - excellent baking potatoes and ideal for French fries

Round reds and long whites usually sold as new potatoes - harvested earlier in the growing season and have a very thin skin

Nutrients in potatoes Rich in carbohydrates (about 25% of the

fresh weight); parenchyma cells within the pith are filled with starch grains.

Low in proteins (only 2.5%) but good protein quality

Fat free - no cholesterol Good source of vitamins, minerals, and fiber

(which occur in the periderm)

Return of Late Blight

Late blight of potato has remained a major pathogen for both potato and tomato

Various fungicides developed to control the fungus

New strains of fungus have recently evolved that are resistant to the effective fungicides

Late blight once again poses a major threat for cultivation of potatoes

Sweet potato - Ipomoea batatas Storage root Vine in the morning

glory family Propagated vegetatively

from “slips” Requires a long, warm,

growing season Susceptible to chilling

injury

Discovered by Columbus Discovered on first voyage - 1492 Introduced to Spain on his return, About 50 years earlier than the introduction

of the white potato Arawak peoples in Caribbean called it batata

corrupted into the word potato Originally “potato” was Ipomoea batatas but

Solanum tuberosum later called that

Sweet potato Following the introduction Widely grown in

Spain and other Mediterranean countries Considered a delicacy in Europe Rumored to be an aphrodisiac, a claim that

was later transferred to the white potato along with the name

Sweet potato Native to tropical South America Cultivation several thousand years in Peru Widely grown as a staple crop in Central America and

tropical South America During this same period also cultivated in several Pacific

Islands and New Zealand An earlier introduction by early seafaring natives? or

natural dispersal of seeds? Thor Heyerdahl's traveled from Peru to Polynesia in the

reed raft Kon Tiki in 1947

Sweet potato today Significant crop throughout the tropics and

expanded to warm temperate regions Used as livestock feed as well as an

important food staple China dominates the world's production Important in several African countries In the United States primarily grown in the

South often called “yams”

Nutrition Rich in carbohydrates and certain vitamins

and minerals - Especially good sources Vitamin A and C Some of the carbohydrates are present in

the form of sugar About 50% more calories than white

potatoes but slightly less protein

Cassava - Manihot esculenta

Tuberous root - member of the spurge family (Euphorbiaceae)

Many names: manioc, tapioca, yuca Vital food for millions in the tropics Ranks fourth as a source of calories for

humans in tropical countries Tapioca pudding only familar cassava

product in US.

Origin and spread of cassava Origins in South America, probably Brazil; May have been independently domesticated

in Central America Well established crop in the New World

tropics long before the arrival of the Europeans

Cultivation today Brazil leading producer in South America Portuguese introduced cassava into West

Africa in the 16th century Extensively cultivated in Africa today Asia, especially Thailand and Indonesia,

closely follows Africa in annual production with South America a distant third

Botany

Tall shrub with numerous tuberous roots that are similar in appearance to sweet potatoes but usually much larger

Propagation Propagated by stem cuttings - none of the

root is used Growth is fairly rapid and little care is

needed following planting Can also be cultivated from seed which can

be a source of new genetic varieties Roots harvested from 8 mos to 2 years

Environmental tolerance Tolerant to a wide range of moisture and soil

conditions From hot lowerlands to cool highlands Requires well drained soils to prevent root rot. Tolerate extended dry periods ( up to 6 mos) Resistant to many insects and fungal pathogens

Processing Once harvested, roots subject to rapid decay

and must be dried or processed by 24 hrs Sweet or bitter varieties based on the

concentration of poisonous hydrocyanic acid (HCN)

If not removed, this toxin can cause death by cyanide poisoning

Cyanogenic glycosides The HCN is liberated by the action of

enzymes upon cyanogenic glycosides present in cassava

Distinction between the sweet and bitter varieties is the concentration of the toxins

Environmental conditions are known to influence the production of cyanogenic glycosides

Removing the toxins Sweet varieties with low HCN levels can be

eaten with little preparation; peeling followed by boiling, steaming, or frying

Bitter varieties must undergo extensive preparation to detoxify before eating

Traditional methods of treating the peeled bitter roots vary and include drying, soaking, boiling, grating, draining, and fermenting, or combinations

Traditional preparation In South America, the traditional preparation

produces a meal called farinha Peeled roots are grated and squeezed through a

long cylindrical woven basket known as a tipiti One end of the tipiti is tied to a tree while the

other end is tied to a pole which is used to stretch the tipiti, thereby expressing juice from the grated pulp

Cassava Bread

Grated cassava meal is used to prepare a flat bread

Nutrients Starch is the main

nutrient - approximately 30% of the fresh weight

Very low in protein (1% or less) and

Can result in kwashiorkor - among peoples who rely on cassava exclusively

Other uses of cassava Asia and the Americas also used for animal feed

and for commercial starch production Cassava starch has many applications in the food,

textile, paper, and pharmaceuticals Tapioca pudding made by cooking tapioca pearls

with milk, eggs, sugar, and vanilla The pearls are partly gelatinized cassava starch

made by heating moist cassava flour in shallow pans

Yams - Dioscorea spp. True yams - Tuber crop Important staples in many areas:

– West Africa, southeast Asia, Pacific Islands, and Caribbean Islands

Genus has several hundred species of which ten are major food sources

Yams have been cultivated for over 5000 years in tropical Africa.

Yams Tubers vary from size of potatoes to

massive ones often weighing over 80 lbs Prepared in ways similar to potatoes 20% starch with about 2% protein Medically the tubers were an important

source of sapogenins, a type of steroid used to make human sex hormones and cortisone

Taro - Colocasia esculenta Corm (underground storage stem) Member of the Araceae or arum family Related to and resembles elephant's ears Poi - the traditional dish of the native

Hawaiians prepared from taro Foods are also wrapped and cooked in the

leaves during a Hawaiian feast or luau

Preparation Corms are steamed, mashed, made into a

dough, and allowed to ferment to prepare poi

Taro may also be cooked in ways similar to potatoes or processed into flour, chips, and breakfast foods

Nutritionally - around 25% carbohydrate, 2% protein and very little fat

Bananas Good source of energy

since it’s rich in starch Some converted to

sugar as the fruit ripens

Good source of potassium

Bananas: the starchy fruit Important dietary staple for millions in

tropical countries Bananas are true fruits Starchy plantains are traditionally cooked and

eaten as a vegetable Africa leader in plaintain production Cultivation of sweet banana greatest in

Central America

Origin and early domestication Native to southeast Asia Among the first cultivated plants in area Polynesians spread the banana throughout

the Pacific islands Cultivated in India for at least 2500 years

Spread of banana Arabian traders introduced bananas into parts

of Africa about 2000 yrs ago Word "banana" comes from West Africa Portuguese and Spanish colonizers spread

bananas throughout tropical regions Early in the 16th century they were

introduced to the New World Became established very early

Early 20th century United Fruit Company (and other companies)

developed extensive banana plantations in Central America along with corporate-run railroads and steamships

For 50 yrs United Fruit exerted control over the economies and governments of several countries - "banana republics"

Rise of nationalism starting in the 1950s led to the decline of United Fruit

Botany of banana Produced by various species in the genus

Musa in the Musaceae, the banana family. Most cultivars are sterile triploids Need tropical climate and constant moisture Cultivated for the fruit, the fiber or even the

foliage which is often used to wrap foods

Banana plant Often called a tree but large herbaceous

monocot May be 20 ft or more in height "Trunk" not woody but is actually a rosette

of overlapping, tightly packed leaf bases which arise from an underground corm.

Large leaves

Fruit production Apical meristem converts from vegetative growth

to flowering Single monoeocious inflorescence develops Flowering stalk contains 5 to 13 groups of flowers

(often called hands or bunches) Most groups contain female flowers that develop

parthenocarpic fruit Male flowers confined to the end of the

inflorescence

Fruit Production

Propagation Fruit production ends the life of a plant New suckers develop from the corm Since the fruits are seedless these suckers

are used in vegetative propagation Suckers reach maturity in 9 to 12 months

Starchy Staples

Starchy staples are an important source of food for people in every area of the world

These starchy staples as well as many of the starchy grains are also grown for many non-food uses as well

Other uses for starch Adhesives

– cardboard, paper bags, gums for envelopes and stamps

Sizings (fillers or coatings)– manufacture of paper, cloth, thread, and yarn

– strengthen the material, impart a smooth finish, or prepare the surface for dyes

Pharmaceutical industry as a binding and coating Laundry starch Production of sugar-based sweeteners The fermentation by yeast produces alcohol

Summary Modified stems and storage root function as food

reserves, for asexual reproduction, and storage Starchy staples include some of the world's

foremost crops and play major roles in the human diet

Potato pivotal to developing societies from the ancient Incas in South America to the pre-industrial countries of Europe, especially 19th century Ireland