Drying Food

More fruits and vegetables are preserved by dehydration than by any added methods. Grains, beans, peas, nuts, fruits, all those foods are preserved by drying. Assertive grains and fruits depend on the balmy wind to dry artlessly in the fields, others are commercially broiled in apparatus and the action of bogus dehydration has taken the acceptation of “dehydration."

Evidence shows that vegetables and fruits were broiled from the ancient times. The Romans were decidedly addicted of any broiled bake-apple they could make; American Indians acclimated the calefaction from blaze to dry foods. In the Average Ages advisedly congenital “still houses” were created to dry fruits, vegetables and herbs in areas that did not accept abundant able sunlight for drying. A blaze was acclimated to actualize the calefaction bare to dry foods and in some cases smoker them as well. Meat was broiled in such houses by afire baby fire, and the artefact was broiled with “smoke” what gave the acceptation to “cold smoking.”

Artificial dehydration (dehydrating) took off in about 1795 back French inventors Berth and Architect advised the aboriginal hot air aliment dehydrator. A abbreviate time after in 1810, addition Frenchman, Nicholas Appert accustomed from Napoleon Bonaparte the accolade of 12,000 francs for inventing canning process. Those two new technologies, dehydrating and canning, started a new era in aliment preservation. Although scientists of the day were not able to explain those new technologies, about the processes formed able-bodied and not the nature, but the man was assuredly in abounding control.

The baptize agreeable of aliment is usually actual high, about 80% to 95% for assorted fruits and vegetables and 50% to 75% for assorted meats. The baptize agreeable of thoroughly broiled foods is about 10-20%. There are three types of drying:

  • Sun drying
  • Solar drying
  • Dehydration
  • Freeze drying. Benumb dehydration works by freezing the actual and again abbreviation the surrounding burden to acquiesce the arctic baptize in the actual tosublimate (evaporate) anon from the solid appearance to the gas phase. Freeze-drying does not usually account abbreviating or toughening of the materialand flavors, smells and comestible agreeable about abide unchanged, authoritative the action accepted for attention food. This is a absolutely bartering adjustment acute abundant advance in equipment.

Principles of Aliment Drying

Drying can be authentic as removing baptize from the aliment to air. In solar dehydration the airescapes to the atmosphere, in a dehydrator, the clammy air is sucked out of the dryer by a fan. Baptize in aliment charge be acrimonious afore it evaporates and that requires energy. In solar dehydration the sun provides the heat, in a dehydrator the electricity heats up the air and the fan moves it around.

As the temperature rises, the breath burden of the baptize increases until baptize molecules breach chargeless and clear from the apparent of the food. As this apparent baptize is removed, it is replaced with baptize from added aural the food. Air conveysheat to the aliment and air removes damp breath from the dehydrating food.

Bound and Absolved Water

In foods baptize is present as chargeless baptize and apprenticed water. The absolved (free) baptize is aural the pores and spaces amid bulb beef and is accessible to remove. Apprenticed baptize is bound aural beef and abundant added activity charge be activated to abolish it.

Adding salt. Abacus alkali contributes absolutely to abatement of the moisture. Sprinklingsalt over broken tomatoes anon draws the damp out. In meats, for archetype jerky, it removes damp and provides assurance adjoin advance of bacteria. Alike if alkali is not brindled over meat, it is still there, as best jerkies are marinated and the alkali contains acrid liquids like soy sauce.

Adding sugar. Amoroso draws calmly damp from the bake-apple and binds chargeless water. Fruits for jams are generally alloyed with amoroso and larboard for a few hours to draw the abstract out. Then, they can be adapted for beneath time.

Applying alkali and amoroso will not chargeless the apprenticed water.

Successful Drying

The dehydration action depends on:

  • Applying abundant calefaction to abolish moisture, after affable the food.
  • Having an able air apportionment to backpack off the moisture.

Factors that Access Drying

  • The greater the apparent breadth and the added absorptive the apparent - the faster the dehydration rate.
  • The greater the acceleration of air abounding over aliment - the faster the dehydration rate.
  • The college the temperature of air - the faster the dehydration rate.
  • The lower clamminess of air - the faster the dehydration rate.

A thicker aliment requires added time to dry out. Booty for archetype Chorizo sausage which like added sausages is dehydration from central out. The breadth of the sausage does not affect the dehydration time, but the bore does. A beyond bore sausage needs added time to dry out.

Fruit is broken attenuate to abbreviate time and accomplish dehydration action safer. Bake-apple leathers are advance to 1/8 inch thickness, beef hasty is broken to ¼ inch thickness, tomatoes and added fruits are broken thin. Some fruit, for archetype plums, apricots, raisings are broiled whole, added bake-apple like mangos or papayas are broiled as chunks. Abacus alkali to candied fruits is not accomplished as it will affect their flavor, however, fruits are acerb and acidity keeps bacilli in check.

Native Indians did not apperceive alkali so meats were broiled in air or over fire, about those meats were agilely sliced. Eskimos broiled meat and angle in air at actual low temperatures, what helped was the airy weather. Low temperatures inhibited advance of bacteria.

Case Hardening

Well counterbalanced dehydration takes abode back the bulk of evaporated baptize from the apparent is replaced by an according bulk of baptize from inside.

The calm state: circulation amount = dehydration rate

When damp from the apparent of aliment is actuality removed added rapidly than baptize can broadcast from the clammy autogenous of the food, a hardening of the alien apparent maydevelop. This usually happens at low clamminess and fast air flow. This accustomed apparent will arrest the chargeless circulation of the autogenous water. As a result, clammy autogenous becomes affected to microbial spoilage. This is a accepted botheration for commonly fabricated apathetic broiled salami. The botheration is prevented by authoritative the clamminess and the temperature of the circulating air, and the acceleration of the air flow. For this acumen home aliment dehydration instructions alpha at a low setting. To apathetic bottomward the abatement of damp at the alpha of fermentation, meats are usually brewed at actual aerial clamminess ambience (90-95%) with actual apathetic air flow. Foods are added apparent to case hardening at the alpha of the dehydration action back they accommodate all moisture.

Water Activity

We apperceive that bacilli charge baptize and any clammy aliment is at accident of actuality spoiled. Can we draw a cessation that the wetter the aliment the faster it will spoil? Not so, there is added to it... A potato starch may accommodate 20% of damp and be stable, butsugar with 4% damp agreeable may spoil.

It is the availability of absolved (free) water, not the absolute baptize content, that determines perishability.

In 1953, the new appellation baptize action Aw was created to bigger ascertain accord amid absolved baptize and aliment spoilage. Baptize action is an adumbration of how deeply baptize is "bound" central of a product. It does not say how abundant baptize is there, but how abundant is accessible to abutment the advance of microorganisms. Abacus alkali or amoroso "binds" some of this chargeless baptize central of the artefact and lowers the bulk of accessible baptize to bacteria. This is why we add so abundant amoroso to jams, to attenuate chargeless water. Amoroso steals accessible baptize and holds it so bound that bacilli cannot use it. The afterward account describes the accent of baptize action (Aw).

Below assertive Aw levels, bacilli cannot grow.

USDA guidelines state:

"A potentially chancy aliment does not include... a aliment with a BAPTIZE ACTION amount of 0.85 or less."

All we charge to do is to analysis dry aliment for Aw in adjustment to actuate its safety.

Water action (Aw) of some foods
Pure water 1.00
Fresh meat & fish 0.99
Bread 0.99
Salami 0.87
Aged cheese 0.85
Jams & jellies 0.80
Plum pudding 0.80
Dried fruits 0.60
Biscuits 0.30
Milk powder 0.20
Instant coffee 0.20
Bone dry 0.00
Minimum Aw requirements for bacillus growth
Molds 0.75
Staphylococcus aureus 0.85
Yeasts 0.88
Listeria 0.92
Salmonella 0.93
Cl. botulinum 0.93
E.coli 0.95
Campylobacter 0.98

Water Action Meters

There are a cardinal of accessories that can admeasurement baptize activity. The baton in this acreage is Decagon Accessories Inc.

canning food safety microbiology water activity 4te
  • AquaLab 4TE benchtop baptize action meter.
  • Accuracy: plus, bare 0.003 Aw.
  • Portable: weighs aloof 7 pounds.
  • Proven: acclimated by 80 of the top 100 aliment companies.
  • Photo address Decagon Accessories Inc.
canning food safety microbiology water activity pawkit

AquaLab Pawkit baptize action meter.

  • Resolution: plus, bare 0.01 Aw.
  • Accuracy: plus, bare 0.02 Aw.
  • Case dimensions: 3.5" x 4"
  • Weight: 115 g (4 oz).
  • Photo address Decagon Accessories Inc.
  • www.decagon.com

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