Dictionary Definition
dried adj
1 not still wet; "the ink has dried"; "a face
marked with dried tears"
2 preserved by removing natural moisture; "dried
beef"; "dried fruit"; "dehydrated eggs"; "shredded and desiccated
coconut meat" [syn: dehydrated, desiccated]dry adj
1 free from liquid or moisture; lacking natural
or normal moisture or depleted of water; or no longer wet; "dry
land"; "dry clothes"; "a dry climate"; "dry splintery boards"; "a
dry river bed"; "the paint is dry" [ant: wet]
2 humorously sarcastic or mocking; "dry humor";
"an ironic remark often conveys an intended meaning obliquely"; "an
ironic novel"; "an ironical smile"; "with a wry Scottish wit" [syn:
ironic, ironical, wry]
3 opposed to or prohibiting the production and
sale of alcoholic beverages; "the dry vote led by preachers and
bootleggers"; "a dry state" [ant: wet]
4 not producing milk; "a dry cow" [ant: wet]
5 (of wines) not sweet because of decomposition
of sugar during fermentation; "a dry white burgundy" [ant: sweet]
6 without a mucous or watery discharge; "a dry
cough"; "that rare thing in the wintertime; a small child with a
dry nose" [ant: phlegmy]
7 not shedding tears; "dry sobs"; "with dry
eyes"
8 lacking interest or stimulation; dull and
lifeless; "a dry book"; "a dry lecture filled with trivial
details"; "dull and juiceless as only book knowledge can be when it
is unrelated to...life"- John Mason Brown [syn: juiceless]
9 used of solid substances in contrast with
liquid ones; "dry weight"
10 unproductive especially of the expected
results; "a dry run"; "a mind dry of new ideas"
11 having no adornment or coloration; "dry
facts"; "rattled off the facts in a dry mechanical manner"
12 (of food) eaten without a spread or sauce or
other garnish; "dry toast"; "dry meat"
13 suffering from fluid deprivation; "his mouth
was dry"
14 having a large proportion of strong liquor; "a
very dry martini is almost straight gin"
15 lacking warmth or emotional involvement; "a
dry greeting"; "a dry reading of the lines"; "a dry critique"
16 practicing complete abstinence from alcoholic
beverages; "he's been dry for ten years"; "no thank you; I happen
to be teetotal" [syn: teetotal] n : a reformer who
opposes the use of intoxicating beverages [syn: prohibitionist]
Verb
2 become dry or drier; "The laundry dries in the
sun" [syn: dry out] [also:
dried, dryest, dryer, driest, drier]dried See dry
User Contributed Dictionary
English
Pronunciation
Adjective
- without water or moisture.
Synonyms
Translations
- Finnish: kuiva
Extensive Definition
- For the food conservation method, see drying (food).
In the most common case, a gas stream, e.g., air,
applies the heat by convection and carries away the vapor as
humidity. Other
possibilities are vacuum drying, where heat is supplied by contact
conduction
or radiation (or
microwaves) while the
produced vapor is removed by the vacuum system. Another indirect
technique is drum drying, where a heated surface is used to provide
the energy and aspirators draw the vapor outside the room.
Freeze drying or lyophilization is a drying
method where the solvent is frozen prior to drying and is then
sublimed, i.e., passed to the gas phase directly from the solid
phase, below the melting point of the solvent. Freeze drying is
often carried out under high vacuum to allow drying to proceed at a
reasonable rate. This process avoids collapse of the solid
structure, leading to a low density, highly porous product, able to
regain the solvent quickly. In biological materials or foods,
freeze drying is regarded as one of the best if not the best method
to retain the initial properties. It was first used industrially to
produce dehydrated vaccines, and to bring dehydrated blood to
assist war casualties. Now freeze drying is increasingly used to
preserve some foods, especially for backpackers going to remote
areas. The method may keep protein quality intact, the same as the
activity of vitamins and bioactive compounds.
In turn, the mechanical extraction of the
solvent, e.g., water, by centrifugation, is not
considered "drying". The ubiquitous term dehydration may mean drying
of water-containing products as foods, but its meaning is more
vague, as it is also applied for water removal by osmotic drive from a salt or
sugar solution. In medicine, dehydration is the situation by which
a person loses water by respiration,
sweating and evaporation and does not
incorporate, for whatever reason, the "make-up" water required to
keep the normal physiological behavior of
the body.
Drying may be either a natural or an intentional
process.
The process of extreme drying is called desiccation.
There is very extensive technical literature on
this subject, including several major textbooks and a dedicated
scientific journal (Drying Technology http://taylorandfrancis.metapress.com/link.asp?id=107829).
Methods of drying
- Application of heated air (convective or direct drying). Air heating reduces air relative humidity, which is the driving force for drying. Besides, higher temperatures speed up diffusion of water inside the solids, so drying is faster. However, product quality considerations limit the applicable rise to air temperature. Too hot air almost completely dehydrates the solid surface, so internal pores shrink and almost close, leading to crust formation or "case hardening".
- Indirect or contact drying (heating through a hot wall), as drum drying, vacuum drying.
- Dielectric drying (radiofrequency or microwaves being absorbed inside the material) It is the focus of intense research nowadays. It may be used to assist air drying or vacuum drying.
- Freeze drying Is increasingly applied to dry foods, beyond its already classical pharmaceutical or medical applications. It keeps biological properties of proteins, and retains vitamins and bioactive compounds. Pressure may be reduced by a vacuum pump. If using a vacuum pump, the vapor produced by sublimation is removed from the system by converting it into ice in a condenser, operating at very low temperatures, outside the freeze drying chamber.
- Supercritical drying (superheated steam drying) involves steam drying of products containing water. Strange as it seems, this is possible because the water in the product is boiled off, and joined with the drying medium, increasing its flow. It is usually employed in closed circuit and allows a proportion of latent heat to be recovered by recompression, a feature which is not possible with conventional air drying, for instance. May have potential for foods if carried out at reduced pressure, to lower the boiling point.
- Natural air drying takes place when materials are dried with unheated forced air, taking advantage of its natural drying potential. The process is slow and weather-dependent, so a wise strategy "fan off-fan on" must be devised considering the following conditions: Air temperature, relative humidity and moisture content and temperature of the material being dried. Grains are increasingly dried with this technique, and the total time (including fan off and on periods) may last from one week to various months, if a winter rest can be tolerated in cold areas.
Applications of drying
Hundreds of millions of tonnes of wheat,corn,
soybean, rice other grains as sorghum, sunflower seeds,
rapeseed/canola, barley, oats, etc., are dried in grain
dryers. In the main agricultural countries, drying comprises
the reduction of moisture from about 17-30%w/w to values between 8
and 15%w/w, depending on the grain. The final moisture content for
drying must be adequate for storage. The more oil the grain has,
the lower its storage moisture content will be (though its initial
moisture for drying will also be lower). Cereals are often dried to
14% w/w, while oilseeds, to 12.5% (soybeans), 8-9% (sunflower) and
9% (peanuts). Drying is carried out as a requisite for safe
storage, in order to inhibit microbial growth. However, low
temperatures in storage are also highly recommended to avoid
degradative reactions and, especially, the growth of insects and
mites. A good maximum storage temperature is about 18°C. The
largest dryers are normally used "Off-farm", in elevators, and are
of the continuous type: Mixed-flow dryers are preferred in Europe,
while Cross-flow dryers in the USA. In Argentina, both types are
usually found. Continuous flow dryers may produce up to 100 metric
tonnes of dried grain per hour. The depth of grain the air must
traverse in continuous dryers range from some 0.15 m in Mixed flow
dryers to some 0.30 m in Cross-Flow. Batch dryers are mainly used
"On-Farm", particularly in the USA and Europe. They normally
consist of a bin, with heated air flowing horizontally from a
narrow-diameter cylinder through a perforated metal sheet, placed
in the center of the bin. Air passes through a path of grain some
0.50 m deep in radial direction and leaves the system through
another perforated sheet. The usual drying times range from 1 h to
4 h depending on how much water must be removed, the air
temperature, and the grain depth. In the USA, continuous
counterflow dryers may be found on-farm, adapting a bin to slowly
drying the grain, and removing the dried product using an auger.
Grain drying is an active area of manufacturing and research. Now
it is possible to "simulate" the performance of a dryer with
computer programs based on equations that represent the physics and
physical chemistry of drying. Drum
Drying
The drum dryer technology has kept its position
of importance. Today, in foods, potato puree is dehydrated as well
as banana and tomato purees to produce dehydrated flakes
Spray drying is an important technique to produce
dried powders. The principle is that a pumpable feed is first
atomized, i.e, converted in a fog of droplets of about 100
micrometers in diameter, which dry very fast while falling by
gravity, accompanied by heated air. The dried particles eventually
exit through the bottom of the dryer and is separated from the
drying air by a cyclone, or a system based on cyclones plus bag
filters or electrostatic precipitators. Milk powder is possibly the
most popular product, and tomato powder is becoming very important.
On the other hand, washing powder is an example product of the
chemical process industry. The production of dehydrated natural
flavors and essences is very important and is growing together with
encapsulation, a technique devised to trap a volatile, but large
molecule (as the flavor compound) inside a dry particle, the walls
of which develop on drying and are permeable to water flux but not
to the flux of the larger volatiles. This principle of selective
diffusion was first developed by the Dutch researcher Thijssen, in
Eindhoven, during the 1970's. Spray dryers differ in the type of
atomizer, the relative directions of air and product flows, the
chamber design, type of drying agent (air, nitrogen) in the system
charactersitics ( closed or open circuit), among other features.
Equipment can be very large, of up to 20 m tall.
- Devices commonly called dryers are used for efficient drying of various things: hair after a shower, candies at candy factories, semiconductor wafers
- Most processes giving a solid product involve a drying step
- Drying is often used to preserve food
- The production of anhydrous alcohol requires azeotropic distillation, or a membrane process. The 96° mixture of ethanol-water cannot be separated by distillation, as it constitutes an azeotrope ("boiling without variation", from the Greek)
- Wood drying is an integral part of timber processing
See also
External links
dried in Bosnian: Sušenje
dried in German: Trocknung
dried in French: Séchage
dried in Dutch: Drogen
dried in Portuguese: Secagem
dried in Finnish: Haihdutus
dried in Chinese: 干燥
Synonyms, Antonyms and Related Words
adust,
baked, burnt, corky, dehydrated, desiccated, dried-up,
evaporated, exsiccated, mummified, parched, scorched, sear, seared, sere, shriveled, sun-dried, sunbaked, weazened, wind-dried, withered, wizened