Chaff

Chaff

[chaf, chahf]

Chaff (or /tʃæf/, depending on dialect – both to rhyme with "half") is the inedible, dry, scaly protective casings of the seeds of cereal grain, or similar fine, dry, scaly plant material such as scaly parts of flowers, or finely chopped straw. In agriculture chaff is used as livestock fodder, or is a waste material ploughed into the soil or burnt.

Etymology

"Chaff" comes from Middle English chaf, from Old English ceaf; related to Old High German cheva meaning husk.

Grain chaff

In grasses (including cereals such as rice, barley, oats and wheat), the ripe seed is surrounded by thin, dry scales 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, emmer and spelt 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 using the wind to blow the lighter chaff aside from grain tossed in the air.

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.

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".

References

See also

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