Difference between revisions of "AY Honors/Palm Trees/Answer Key"

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Revision as of 18:36, 11 March 2007

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For the mining disaster, see Sago Mine disaster.

Sago is a powdery starch made from the processed pith found inside the trunks of the Sago Palm Metroxylon sagu. Metroxylon is the scientific name derived from Greek and means heartwood. The species name is from a local name for the food. Sago forms a major staple food for the lowland peoples of New Guinea and the Moluccas where it is often cooked and eaten as a form of pancake with fish.

Sago looks like tapioca and both are pearly grains of starch, but tapioca is made from the root of the cassava plant. They are similar but are not identical when used in recipes.

Because sago flour made from Metroxylon is the most widely used form, this article discusses sago from Metroxylon unless otherwise specified.

Sago palms grow very quickly, up to 1.5m of vertical stem growth per year, in the fresh water swamps and lowlands in the tropics. The stems are thick and either self supporting or grow with a somewhat climbing habit. The leaves are pinnate, not palmate. They are harvested at the age of 7 to 15 years just before they flower. They only flower and fruit once before they die. When harvested the stems are full of the stored starch which would otherwise be used for flowering and fruiting. The trunks are cut into sections and into halves and the starch is beaten or otherwise extracted from the "heartwood", and in some traditional methods it is collected when it settles out of water. One palm yields 150 to 300kg of starch.

Preparation

Sago (Metroxylon) is made through the following steps:

  1. Felling the sago palm tree;
  2. Splitting the trunk open lengthwise;
  3. Removing the pith;
  4. Crushing and kneading the pith to release the starch;
  5. Washing and straining to extract the starch from the fiberous residue;
  6. Collection of the raw starch suspension in a settling container.

The sago starch is then either baked (resulting in a product analogous to bread or a pancake) or mixed with boiling water to form a kind of paste. Sago can be made into steamed puddings such as sago plum pudding, ground into a powder and used as a thickener for other dishes, or used as a dense glutinous flour.

The starch has also been used to treat fibre to make it more easier to machine. This process is called sizing and helps to bind the fibre, give it a predictable slip for running on metal, standardise the level of hydration of the fibre, and give the textile more body. Most cloth and clothing has been sized and is removed in the first wash.

In Malaysia and Indonesia, sago from Metroxylon is used as a starch in making noodles, white bread, and sago pearls (similar to tapioca). In India pearl sago (a form of sago) is called Sabudana, and is used in a variety of dishes including khichdi, wafers and puddings. The source of this sago is most likely Metroxylon rather than the cycad version, and is sago not tapioca.

Nutrition

Sago flour (Metroxylon) is nearly pure carbohydrate and has very little protein, vitamins, or minerals. However, as sago palms are typically found in areas unsuited for other forms of agriculture, sago cultivation is often the most ecologically appropriate form of land-use, and the nutritional deficiencies of the food can often be compensated for with other readily available foods.

One hundred grams of dry sago yields 355 calories, including an average of 94 grams of carbohydrate, 0.2 grams of protein, 0.5 grams of dietary fiber, 10mg of calcium, 1.2mg of iron, and negligible amounts of fat, carotene, thiamine, and ascorbic acid.

Sago can be stored for weeks or months, although generally it is eaten quickly after it is processed.

Other Uses

In addition to its use as a food source, the leaves and spathe of the sago palm are used for construction materials, for thatching roofs, and the fibre can be made into rope.

Botany

The palm genus Metroxylon has several species. The main source of sago flour is Metroxylon sagu. It is found in Southeast Asia, New Guinea, and some islands in Micronesia and Polynesia. Growing up to 30 meters in height, the sago palm is found in tropical lowland forest and freshwater swamps, and can grow in a wide variety of soils.

Cycad Sago

The Sago Cycad or "Sago Palm" (its common name but a misnomer since it is not an actual palm at all) is a slow-growing wild or ornamental plant.

Processed starch known as sago is made from this and other cycad plants, and is a less frequent food source for some peoples of the Pacific and Indian Oceans. There is a large difference both biologically and dietarily between the two types of sago. Sago as a major dietary food source comes mainly from a palm in the genus Metroxylon. Despite their common name, cycads are not palms (i.e. they are not members of the family Arecaceae but rather from Cycadaceae, a vastly different taxonomic order: cycads are gymnosperms, sometimes called living fossils, while palms are angiosperms).

Sago from the cycad is very different, because unlike Metroxylon, cycad seeds contain highly poisonous compounds. Consumption of cycad seeds has been implicated in the outbreak of Parkinson's Disease-like neurological disorder in various locations in the Pacific such as Guam. Highly toxic cycasin and BMAA compounds are found in most parts of the plant. These must be removed through extended processing before any part can be safely eaten. First, the pith made from the trunk, root, seeds is first ground to a coarse flour, washed carefully to leach out natural toxins, then dried and cooked to become a starchy granular fecula similar to tapioca and is used for many of the same purposes.

References

External links

de:Sago la:Sagum (cibus) nl:Sago pl:Sago pt:Sagu sv:Sago zh:西米

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