Sekam
Sekam adalah bagian dari bulir padi-padian (serealia) berupa lembaran yang kering, bersisik, dan tidak dapat dimakan, yang melindungi bagian dalam (endospermium dan embrio). Sekam dapat dijumpai pada hampir semua anggota rumput-rumputan (Poaceae), meskipun pada beberapa jenis budidaya ditemukan pula variasi bulir tanpa sekam (misalnya jagung dan gandum).
Dalam pertanian, sekam dapat dipakai sebagai campuran pakan, alas kandang, dicampur di tanah sebagai pupuk, dibakar, atau arangnya dijadikan media tanam.
Anatomi
Secara anatomi, sekam terbentuk dari bagian perhiasan bunga padi-padian (spikelet) yang disebut gluma, palea, dan lemma. Pada tongkol jagung konsumsi, ketiga bagian ini tereduksi sehingga tampak seperti sisik pada permukaan tongkol. Pada padi, gluma mirip seperti dua duri kecil di bagian pangkal. Palea adalah bagian penutup yang kecil, sedangkan lemma adalah bagian penutup yang besar dan pada varietas tertentu memiliki "bulu" (awn). Pada bunga gandum, ketiga bagian ini berkembang baik.
Sekam diperlukan untuk keperluan penanaman ulang tanaman ini. Bulir tanpa sekam (disebut beras bagi padi) tidak dapat digunakan sebagai bahan tanam, kecuali untuk kultivar tanpa sekam.
Grain chaff
In grasses (including cereals such as rice, barley, oats and wheat), the ripe seed is surrounded by thin, dry scaly bracts (called glumes, lemmas and paleas), forming a dry husk, the chaff.
Domesticated types of grain have been bred to have chaff which is easily removed. For example, in wild species of wheat and in the primitive domesticated einkorn,[1] emmer[2] and spelt[3] wheats, the grains are hulled – the husks enclose each seed tightly. Before the grain can be used, the hulls must be removed by further processing such as milling or pounding. In contrast, in free-threshing (or naked) forms such as durum wheat and common wheat, the glumes are fragile, and on threshing the chaff easily breaks up, releasing the grains.
The process of loosening the chaff from the grain is called threshing, and separating the loose chaff from the grain is called winnowing – traditionally done by tossing grain up into lightly blowing wind, dividing it from the lighter chaff, which is blown aside. This process typically utilizes a broad, plate-shaped basket, or similar receptacle for holding and collecting the winnowed grain as it comes back down.
Chaff should not be confused with bran, which is finer, scaly material forming part of the grain itself.
Straw chaff
Chaff is also made by chopping straw (or sometimes coarse hay) into very short lengths, using a machine called a chaff cutter. Like grain chaff this is used as animal feed, and is a way of turning coarse fodder into a form more palatable to livestock.[4][5][6][7][8]
Botany
In botany, chaff refers to the thin receptacular bracts of many species in the sunflower family Asteraceae and related families. They are modified scale-like leaves surrounding single florets in the flower-head.
Metaphor
Chaff as a waste product from grain processing leads to a metaphorical use of the term, to refer to something seen as worthless. This is most commonly in the expression "to separate the wheat from the chaff" from Matthew 3., where it means to separate things of value from things of no value. Another example is in Psalm 1 of the Bible, which says: "Not so the wicked! They are like chaff that the wind blows away".
See also
- ^ Potts, D. T. (1996) Mesopotamia Civilization: The Material Foundations Cornell University Press. p. 62. ISBN 0-8014-3339-8.
- ^ Nevo, Eviatar & A. B. Korol & A. Beiles & T. Fahima. (2002) Evolution of Wild Emmer and Wheat Improvement: Population Genetics, Genetic Resources, and Genome.... Springer. p. 8. ISBN 3-540-41750-8.
- ^ Vaughan, J. G. & P. A. Judd. (2003) The Oxford Book of Health Foods. Oxford University Press. p. 35. ISBN 0-19-850459-4.
- ^ "The Chaff cutter"
- ^ Cutting chaff by hand: detail of painting by David Teniers the Younger
- ^ A Victorian chaff cutter
- ^ Virtual Victorians (Accessed 12 May 2008)
- ^ Modern chaff cutter, Maharashtra Industries Directory. (Accessed 12 May 2008)