Transcript Home Drying Basics - Utah State University Extension

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Home Drying Basics
Created by: Kathleen Riggs
USU Extension Agent, Iron County
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Drying (Dehydration)
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One of the oldest methods of preserving food
Alternative to canning & freezing
Simple, safe and easy to learn
Can dry food year round
No refrigeration needed
Takes little space
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How Drying Preserves Food
• Removes moisture stops the growth of
bacteria, yeasts & molds that normally spoil
food
• Slows down but doesn’t completely inactivate
enzymes
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Temperatures for Drying
• The ideal temperature for drying
or dehydrating foods is 140° F
– If higher temperatures are used,
food cooks instead of drys
• Avoid “case hardening”
– dried on outside but moisture
trapped inside allowing mold
growth
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Climate Controls
• Low humidity aids drying
• Utah average relative humidity in Summer is 20%
• Illinois average relative humidity in Summer is 50-80%
• Increasing the air flow with fans speeds up the
drying process- removes air pockets around
food
• Consecutive days of sunshine
• Iron Co., UT has over 255
days per year
• Washington Co., UT has 300
sunny
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Methods for Drying Food
• Outdoors (Sun & Solar)
– Works well in Southern Utah
• June - September
• Oven
– Need temperature of 160° F and frequent rotation
• Dehydrator
– Easiest method and most efficient but may have
smallest capacity
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Drying Foods Outdoors
• Sun Drying:
– Fruits safe to dry due to high acid and sugar
content
– Vegetables & meats should not be dried outside
• They need constant temperature & airflow
– Temperature of 85° F or higher for several days
with humidity below 60%
– Cover to protect against insects/pests
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Drying Outside, continued
• Solar Drying– Need to construct a dryer with
panel(s)
– Need to stir and turn food several
times a day
– Need several days of sun in a row
• Vine Drying– Beans & Lentils
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Drying Foods Indoors
• Methods:
– Food dehydrator
– Counter-top
– Convection Oven
– Conventional Oven
– Microwave Oven
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Food Dehydrators
• These are small electrical appliances for drying
foods indoors
• They contain an electric element for heat, fan
& vents for air circulation
• Some have actual temperature controls but
usually dry at 140° F
• Widely available in stores,
catalogs and on-line
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Common Dehydrator Features
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Plastic or metal (not wood)
Enclosed heating element
Counter top design
Enclosed thermostat
(readings from
85°F- 160°F)
• Fan or blower
• 4-10 open mesh traysmade of sturdy, washable
plastic
• UL Seal of Approval
• 1 year warranty
• Dial/control for
regulating temperature
• A timer, or auto-shutoff
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Types of Air Flow
Horizontal Air Flow
• Heating element and fan
are located on the side
– Major disadvantages:
• Higher priced
• Take up a lot of counter
space
– Major advantages:
• Different foods can be dried
at same time without flavors
mixing
• Equal heat distribution
• No drips on to trays below
Vertical Air Flow
• Heating element and fan on
top or bottom of unit
– Major disadvantages:
• Dries smaller quantities
• Trays need to be rotated
throughout process for equal
drying
– Major advantages:
• Smaller units
• Lower cost
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Oven Drying
• If you use your oven:
– Dial needs to go down to 140°- 160°F
– Leave oven door open 2-6 inches
– Best if you place a fan outside oven door to force
air movement
– Oven cycles on and off- make certain thermostat
is accurate at 140°F
– (Hint: Most ovens don’t go this low)
– Tray size should be 3-4” shorter (front to back);
leave 2-3” between racks
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Oven Drying
• Slower process than using dehydrators, unless
you have a convection range that moves the
air
• Could take twice as long to dry than a
dehydrator… oven is not as efficient and uses
more energy
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Room Temperature Drying
• Method used mainly for herbs & hot peppers
– Strung on string or tied in bundles and suspended
from overhead racks in air until dry OR
– Enclosed in paper bags with openings for air
circulation
– Herbs can also be dried in the microwave oven
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The Process
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Drying Fruit
• Prepare the Fruit- wash, core and peel if
desired
• Fruits can be halved or sliced and some left
whole
• Thin, uniform, peeled slices dry fastest
• If fruit is whole, “check” or crack the skin to
speed drying
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Drying Fruit, continued
• Pre-treatment
– Some fruits need to have enzymes inactivated
before drying– especially those that oxidize when
exposed to air (e.g. bananas, apples, pears)
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Ascorbic Acid
Fruit juice dip
Honey dip
Syrup blanching
Commercial acids
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Arranging Fruit for Drying
• Do not over fill
– Leave room for air circulation
• Lay as flat as possible
• Dry similar fruits together
– Avoid mixing strong odors
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Determining Dryness of Fruit
• Drying fruit can take anywhere from 6 hours for
thin or small pieces or 10-12 hours for larger
juicy fruits such as peach or apricot halves.
• Dried fruit will feel leathery; won’t stick to itself
• Cut fruit should have no visible moisture inside
though it may be soft
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After Drying Fruit…
• Cool fruit 30-60 minutes before packaging…
don’t pack too soon or moisture buildup could
occur… Don’t wait too long or the fruit could
pick up moisture from the air
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Conditioning Fruit
• Conditioning is used to equalize moisture
– Pack cooled fruit in plastic bag or glass jar
– Seal and let stand for 7-10 days
– Shake jars daily to separate pieces and check for
moisture (condensation on sides of bag/jar)
– If there is condensation, return fruit to dehydrator
for more drying or place in freezer
• There is a chance mold will have already started
growing in too-moist fruit- Discard if you find mold.
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Fruit Leathers
• Made from pureed fruit
– Can use fresh/frozen fruit or canned fruit
• May add sugar, honey, or lemon
juice for flavor and color retention
• May add coconut or nuts
• Dry on special drying tray that comes with
dehydrator
• Dry until pliable; no wet spots; not crispy
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Drying Vegetables
• Prepare the vegetables
– Wash, trim, and peel
– Cut uniform pieces or leave whole
– Dry as soon as possible after harvesting
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Pre-treating Vegetables
• Water blanching–
– Follow recommended
times
– Do not over-fill basket or
pan
– Start timing when water
returns to boil after
placing vegetables in
basket
• Steam blanching– Place in basket above
boiling water (no more
than 2 inches higher)
– Cover pan/pot and begin
timing
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Cooling Vegetables
• Dip briefly in cold water only long enough to
stop cooking
• Cool until they are only slightly hot to touch–
about 120° F
• Wipe and spread vegetables out on racks for
drying
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Determining Dryness of Veggies
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Dry vegetables until brittle or “crisp”
Some vegetables shatter if hit hard
Low moisture (10%)
Cool, place in bags or jars and seal
– Should store up to 1 year if in a cool dark place in
jars with air-tight lids
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Jerky
• Use lean meat (cuts of beef, pork, venison, or
smoked turkey breast)
• If wild game is used, freeze meat for 30 days
to kill Trichinella parasite
– If you are raising your own meat, make certain
slaughtered animals do not eat any carcasses of
mice, etc. (mostly hogs)
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Eliminating Illness Causing Bacteria
• Dip meat strips in
boiling marinade 15
seconds before drying–
dry as usual
• Check temperature of
several strips- 160° F is
desired temperature
• Heat dried jerky strips
in oven after drying
process is completed.
• Heat 10 minutes in
oven pre-heated to
275° F. Thicker strips
may take longer.
• Test internal temp.-160° F is target
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Determining Dryness of Jerky
• Jerky should bend and “crack” but not break
• There should be no surface moisture or visible
moisture when cut open
• Will be somewhat chewy
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Storing Jerky
• Properly dried jerky keeps at room temp for 2
weeks in sealed container.
• For best results, to increase shelf life and
maintain best flavor and quality, refrigerate or
freeze jerky and take out as needed
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Nutritional Value of Dried Foods
• Fresh produce provides calories, fiber,
minerals and vitamins. Changes that can be
expected in home-dried food are:
– Calories: No change
– Fiber: No change
– Minerals: Minimal loss
– Vitamins: Greater loss during dehydration process
(more susceptible to heat, air and light)
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Yields
• Because drying removes moisture, the food
shrinks and decreases in size and weight.
When water is added to the dried product, it
returns to its original size
25 lbs. apples = 4 lbs. dried
25 lbs. onions = 3 lbs. dried
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References
• “So Easy to Preserve”- University of Georgia
• Drying Food, University of Illinois Extension
• Food Preservation: DehydrationNew Mexico State University
• Home Drying of Food, Utah State University
Extension
Download:
http://extension.usu.edu/files/publications/publication/
FN-330.pdf
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© Utah State Univ. Extension
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forms of illegal discrimination based on race, color, religion, sex, national origin, age (40 and
older), disability, and veteran’s status. USU’s policy also prohibits discrimination on the basis of
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University employees and students cannot, because of race, color, religion, sex, national origin,
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discriminate in the classroom, residence halls, or in on/off campus, USU-sponsored events and
activities. This publication is issued in furtherance of Cooperative Extension work, acts of May 8
and June 30, 1914, in cooperation with the U.S. Department of Agriculture, Noelle E. Cockett,
Vice President for Extension and Agriculture, Utah State University.
Author: Kathleen Riggs USU Cooperative Extension. August 2008.
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