Chaff (; )
Etymology
"Chaff" comes from
Middle English chaf, from Old English ceaf, related to Old High German
cheva, "husk".
Grain chaff
]]In
Poaceae (including
cereal such as
rice,
barley,
oat, and
wheat), the ripe seed is surrounded by thin, dry, scaly
bracts (called
glume, lemmas, and paleas), forming a dry
husk (or hull) around the grain. Once it is removed, it is often referred to as chaff.
In wild cereals and in the primitive domesticated einkorn,[Potts, D. T. (1996) Mesopotamia Civilization: The Material Foundations Cornell University Press. p. 62. .] emmer[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. .] and spelt[Vaughan, J. G. & P. A. Judd. (2003) The Oxford Book of Health Foods. Oxford University Press. p. 35. .] wheats, the husks enclose each seed tightly. Before the grain can be used, the husks must be removed.
The process of loosening the chaff from the grain so as to remove it is called "threshing" before "drying" – traditionally done by milling or pounding, making it finer like "flour". Separating remaining loose chaff from the grain is called "winnowing" – traditionally done by repeatedly tossing the grain up into a light wind, which gradually blows the lighter chaff away. This method typically uses a broad, plate-shaped basket or similar receptacle to hold and collect the winnowed grain as it falls back down.
Domesticated grains such as durum wheat and common wheat have been bred to have chaff that is easily removed. These varieties are known as "free-threshing" or "naked".
Chaff should not be confused with bran, which is a finer, scaly material that is 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, it is used as animal feed and is a way of making coarse fodder more palatable for livestock.
[ Cutting chaff by hand: detail of painting by David Teniers the Younger][ A Victorian chaff cutter ]
Coffee chaff
Coffee chaff is produced from the so called
silverskin, the thin inner-parchment layer on dried coffee beans, in the process of
coffee roasting.
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
in the flower-head.
Metaphor
Chaff as a waste product from grain processing leads to a
use of the term, to refer to something seen as worthless. In the
Bible, such use is found in Job 13:25,
Isaiah 33:11,
Psalm 83:13-15,
and other places. Chaff also lends its name to a radar countermeasure, composed of small particles dropped from an aircraft.
Use
Hungarian engineer László Schremmer has discovered that the use of chaff-based filters can reduce the
arsenic content of water to 3 microgram/litre. This is especially important in areas where the potable water is provided by filtering the water extracted from an underground
aquifer.
[ Newspaper article (in Hungarian) published by Magyar Nemzet on April 15, 2012.]
See also
