Drying Foods
Jananne Finck, MS, RD.
Nutrition & Wellness Educator
Springfield Center
Drying is New Again
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One of the oldest methods of preserving
food
Alternative to canning & freezing
Simple, safe and easy to learn
Can dry year round
No refrigeration needed
Takes little space
How Drying Preserves
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Removes moisture from food so bacteria,
yeasts & molds can’t grow and spoil food
Slows down action of enzymes but doesn’t
inactivate them
Temperatures for Drying
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Optimum temperature for drying food is
140°F
If higher temps are used, food cooks
instead of drying
Avoid “case hardening” – dried outside
and moisture is trapped inside – mold
results
Helps Drying…
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Low humidity aids drying
Increasing air current speeds up drying,
removes air around food
Ways To Dry Food
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Foods can be dried in the sun, but often
doesn’t work well in Illinois…need several
days of high temp and low humidity
Dry in an oven
Dry in food dehydrator
Drying Out-Of-Doors
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Sun Drying
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Dry fruits, high sugar & acid make them safe
Don’t dry vegetables or jerky/meat outdoors
Need hot, dry, breezy days
Temp of 85ºF. or higher, for several days with
humidity below 60%
Need to cover, watch materials used and
control for insects and pests
Out-Of-Doors
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Solar Drying
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Need to make a dryer
Need to stir and turn food several times a day
Need several days…
Vine Drying
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Dry beans, lentils and soybeans
Leave bean pods on vine until beans inside rattle
If not dried can dry further in oven or dehydrator
Pasteurization
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Freezer Method –
seal food in freezer
plastic bags. Freeze
at 0ºF for at least 48
hours
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Oven Method –
Place food in single
layer on fray or in
shallow pan. Place in
oven preheated to
160ºF for 30 minutes
Drying Foods Indoors
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Food dehydrators
Counter-top
Convection ovens
Conventional ovens
Food Dehydrators
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Small electrical appliance for drying foods
indoors
Electric element for heat & fat and vents
for air circulation
Dry foods fast at 140ºF
Buy at department stores, mail-order,
garden supply, internet
Costs?
Costs vary depending on features.
Some are expandable & extra
trays can be purchased. Twelve
square feet of drying space dries
about a half-bushel of produce.
Major disadvantage of dehydrator
is limited capacity.
Dehydrator Features
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Double wall
construction of
metal or high grade
plastic, not wood
Enclosed heating
element
Counter top design
Enclosed thermostat
from 85ºF-160ºF
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Fan or blower
4-10 open mesh trays,
plastic, sturdy,
washable
UL seal
1 year guarantee
Convenient service
Dial for regulating temp
A timer, auto- shut off
Types of Dehydrators
Horizontal Air Flow –
Heating element and fan
are located on side
Major advantages –
reduces flavor mixing
so different foods can
be dried at once, all
trays get equal heat,
juices don’t drip into
heating element
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Vertical Air Flow –
Heating element and fan
located at base
Major disadvantage –
if different foods dried,
flavors can mix and
liquids can drip into
heating element
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Oven Drying
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Slower than dehydrators, unless you have
a convection oven, which has a fan
Take 2 times longer to dry in oven than
dehydrator…oven not as efficient and
uses more energy
Using Your Oven
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Dial needs to go down to 140ºF
Leave oven door propped oven 2-6 inches
Best if you place a fan outside oven door
Oven temp varies…so need accurate oven
thermometer to be sure 140 is achieved
Trays should clear sides of oven & 3-4”
shorter front to back of oven, 2-3” between
racks in oven
Room Drying
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Herbs, hot peppers, & nuts in shell are
most common air dried foods
Herbs & peppers – strung on string or tied
in bundles and suspended from overhead
racks in air until dry.
Can enclose in paper bags, with openings
for air circulation
Spread nuts in single layer on paper
Drying Fruit
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Preparing the Fruit – wash fruit and core, if
needed
Fruits can be halved or sliced and some left
whole
Thin, uniform, peeled slices dry fastest
Apples can be cored and sliced - wedges, rings
Bananas can be sliced
If fruit dried whole, “check” or crack the skin to
speed drying – cranberries – place in boiling
then cold water to “check”
Pretreating the Fruit
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Sulfuring
Sulfite Dip
Ascorbic Acid
Ascorbic Acid
Mixtures
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Fruit Juice Dip
Honey Dip
Syrup Blanching
Steam Blanching
Drying the Fruit
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Place fruit in single layer
Follow directions given
Follow approximate drying times given
Watch food as it dries much faster at the
end of drying period
Determining Dryness of Fruit
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Most fruit – should have 20% moisture
content when dried
Cut several cooled pieces in half…should
be no visible moisture and should not be
able to squeeze any moisture from fruit
Not be sticky or tacky
If piece folded in half, shouldn’t stick to
itself
After Drying…
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Cool fruit 30-60 minutes before
packaging…don’t pack too soon or
moisture buildup could occur…don’t wait
too long or could pick up moisture
Conditioning Fruits
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Conditioning equalizes the moisture.
Pack cooled fruit in plastic or glass jars,
seal and let stand for 7-10 days
Shake jars daily to separate pieces and
check for moisture condensation
If condensation, return to dehydrator for
more drying…unless has started to mold,
then dispose of
Drying Vegetables
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Preparing the vegetables
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Wash, trim, peel, according to directions
Uniform pieces
Dry as soon as possible after picking
Pretreating Vegetables
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Water blanching –
follow times given,
start counting time as
soon as water returns
to boil. If takes more
than 1 minute to
return to boil, are
putting in too many
vegetables at a time
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Steam blanching –
Vegetables should be
no more than 2
inches deep above
boiling water. Cover
and steam according
to directions given for
each vegetable
Cooling Vegetables
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Dip briefly in cold water only long enough
to stop cooking
Cool to they feel only slightly hot to
touch…about 120ºF
Wipe vegetables and place in dehydrator
Determining Dryness of Veggies
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Dry vegetables until brittle or “crisp”
Some vegetables shatter if hit with
hammer
10% moisture
Don’t need conditioning like fruits, as
lower moisture content
Fruit Leathers
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Fresh Fruit
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Canned or Frozen Fruits
Drying Fruit Leathers
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Pour 1/8-inch thick on drying tray
Take 6-8 hours to dry in dehydrator, up to 18 in
oven
Dry at 140ºF
Dry when no indention in center of leather
When warm, peel from plastic and roll , cool and
rewrap roll in plastic
Keep up to 1 month at room temp, then may
freeze up to 1 year
Jerky
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Lean meat like beef, pork, venison or
smoked turkey breast
If wild game is used, treat to kill Trichinella
parasite by freezing a portion 6 inches or
less thick at 0ºF at least 30 days…this
doesn’t kill bacteria though
Eliminating E. coli O157:H7 Risk
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Heating meat strips in
marinade before
drying – drying times
will be reduced.
Check temp of
several strips with
metal stem-type
thermometer to
determine 160ºF is
reached.
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Heating dried jerky
strips in oven after
drying process is
completed. Heat strips
10 minutes in oven
preheated to 275ºF.
Thicker strips may
take longer heating,
check temp (160ºF)
with thermometer.
Storing Jerky
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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.
Reference
“So Easy To Preserve”
Cooperative Extension Service
The University of Georgia, 4th Edition, 1999.