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STARCHY STAPLES

STARCHY STAPLES . Potato, Sweet potato, Cassava Most of staples popular in Pakistan Starch food reserves in underground organs (roots or modified stem) Starch-polymer of glucose molecule Tropical origin High in carbohydrates, low in proteins. STARCH MOLECULE.

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STARCHY STAPLES

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  1. STARCHY STAPLES • Potato, Sweet potato, Cassava • Most of staples popular in Pakistan • Starch food reserves in underground organs (roots or modified stem) • Starch-polymer of glucose molecule • Tropical origin • High in carbohydrates, low in proteins

  2. STARCH MOLECULE • Amylosepoly-(1-4) glucose, a straight chain • Tends to coil up into a helix • Amylopectin is poly(1-4) glucose with branches • Open molecular structure than amylose • Because it has more ends broken more quickly than amylose by amylase enzymes

  3. Modified Organs • Rhizome underground horizontal stem • Food storage organ • Leaves reduced in form of scales on surface of rhizome • Roots adventitious • Buds on nodes give rise to new plants

  4. Tubers enlarged storage tip of rhizome • White potato • Eyes are buds that form new plant • Bulbs modified storage organs mostly in monocots • Underground stems with fleshy leaves • Onions, Tulips • New bulbs can develop in the leaves axils

  5. White Potatoes • Solanum tuberosum associated with Ireland • Established in 1965 • Dietry staple food for Irish people • Ideal climate and soil for potato • Small plots of land sufficient to feed a family • Historian link population explosion to presence of reliable food

  6. Average adult consumption of potato 4 to 6kg each day • Reliance on potatoes set the disaster: Irish potato famine of 1845-1849 • Pathogen Phytophthora infestans cause of late blight of potato • Fungus attacks leaves, blacken them stopping tuber growth • In cool wet weather, fungus kills plant within a week

  7. Disease appeared in 1845 in Ireland • Widespread destruction of potato crop • 1million people died from starvation • Resulted 20-30% decline of population in Ireland in Ireland in less than a decade • Conflicts between English rulers and Irish people another reason • In history, Ireland a colony of English people and Irish were shamelessly exploited

  8. Solanum tuberosum • Genus Solanum- cultivated potato • 2,000 species in Solanaceae • S. tuberosum 6,000 cultivars • Europe produce 70% of world crop • China second leading producer and next Brazil • Stem of two types • Ordinary foliage bearing stems • Underground rhizome that ends in tubers

  9. Anatomically, tuber modified version of dicot stem • Enlarged pith, a ring of vascular bundle, and narrow cortex • Vascular tissue appear black in potato chips with narrow cortex on outside and large pith within ring • Cool season crop with maximum tuber production ranging under 15to 18C

  10. Higher temperature inhibit tuber production (29C) • Potato cultivation through propagation by seed potatoes, small tubers or cut pieces containing at least one eye • Seed potatoes cultivation- asexual reproduction producing plants genetically identical to their parents and maintaining desired traits within a cultivar

  11. Seed potatoes checked for diseases • Fast method • Disadvantage- Share same susceptibility to adverse environmental conditions • Susceptible to Phytophthora infestans and Colorado potato beetle • Potato beetles became resistant to chemical insecticides used for control

  12. Russet Red Potatoes Varieties white

  13. Round white used for baking, chips, fires • Russets elongate, cylindrical tubers, excellent for baking purposes, common in Pakistan • Russets potatoes high in starch • Round red and long white relatively new • Good for boiling steaming, roasting

  14. Potatoes rich in carbohydrates (25% of fresh weight) • Parenchyma cells within pith filled with starch grains • Vitamin, minerals and fibers in cortex and periderm • Nutritional value enhanced when consumed with skin

  15. Sweet Potatoes • Ipomoea batatus • Storage root in family Convolvulaceae • Habitat vine • Columbus discovered sweet potatoes • Native to South America • China dominating country in production

  16. Drier, starchier variety in Northern States • Sweeter, moist, deep orange (Yams) common in South • Rich in carbohydrates, vitamins and minerals • 50% more calories than white potatoes • Root source of carotene, vitamin A, C • Thanksgiving diet

  17. Bananas • Important dietary staple in in tropical countries • Popular dessert, source of starch and potassium • Sweet banana • Tree habitat • Herbaceous with height of 6meters or 20 feet

  18. Bananas native to Southeast Asia • Cultivated 2500 years • Genus Musa in Musaceae • Require tropical climate with constant moisture • Cultivated for food, fibre, foliage (natural waxed paper)

  19. Banana Tree

  20. Plantains • Important food in poor countries • Planta-sole of foot • Genus Plantago • P. ovata P. afra (Grown in India) • Twice the size of banana • Sour or sweet in taste • Ripe black plantain more sweet than banana

  21. Plantains

  22. Ten times more B-carotene than banana • Source of vitamin A, C, B6, potassium, iron and magnesium • Helpful in treating ulcers • Green, unripe varieties have enzymes for healing

  23. CASSAVA • Manihot esculenta • Family Euphorbiaceae • Known as Manioc, Yuca, Mandioca • Ranks fourth behind rice, sugar and corn as source of calories in tropical countries • Tall shrub with palmately compound leaves • Can tolerate dry period upto 6 moths

  24. CASSAVA Roots Cassava plant

  25. Varieties may be sweet or bitter • Hydrocyanic acid (HCN) • If not removed, toxin may cause death by cyanide poisoning • HCN liberate through enzymatic actions cyanogenic glycosides • Sweet and bitter varieties differ only on cyanide content • Environmental conditions influence cyanide production

  26. Sweet variety can be bitter under different condition • Traditional methods for treating bitter ones varies • May include drying, soaking, boiling, draining • Processed to make flour • In Indonesia, peeled roots sliced, dried in sun, allows HCN to diffuse • Resulting chips called gaplek

  27. Stored for long period of time or ground into flour • Breads, cakes, cookies, noodles • Starch rich (30% of fresh weight) • Protein content is being improved through cassava breeding programmes • Roots also contain calcium, vitamin B and C • Being used for Bioethanol

  28. Recommended Links • http://www.all-about-potatoes.com/types-of-potatoes.html • www.botany.org • http://www.geneconserve.pro.br/bio_rogers.htm • http://www.mrothery.co.uk/biochm/biochmnotes.htm

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