A solar dehydrator designed by
Chas Martin of Willunga. It
features a tiny electric fan to
speed up drying time and is
weatherproof. Dehydration of
most fruit in summer takes 2-3
days.
Chas lives in a solar/wind
powered home at Willunga in
South Australia and besides
running a mechanical workshop
he can export power to his
neighbours. He installs power
systems and composting
toilet/reedbed systems for others.
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The purpose of dehydration is to take out enough
water from the material (and therefore in the case of fruits raise the
natural sugar level) so that spoilage organisms are not able to grow and
multiply during storage. Although ‘drying’, ‘dehydrating’ and ‘evaporating’
are often used casually to mean the same thing, dehydrated food is understood
to contain only 2.5% to 5% water. "Dried" food still contains roughly 10
% to 20% water and in order to keep it, some preservative needs to be added
(or be kept frozen).
Advantages of dehydrated food
· It takes up only 8-30% of it’s original
volume
· Does not rely on power to be stored
· Long shelf life
· Preserving without the need of any additives
Some points about dehydrating using a dehydrator
Drying herbs:<35`C (higher temps cause loss
of flavour)
Drying Fruit and Leathers:<55`C
Drying Veg.:<50`C
Use fruit with good flavor: select fresh fruit
at the peak of ripeness ( if it tastes like cardboard because a fruit is
unripe it will taste like a very dry piece of cardboard later). Wash
thoroughly and dry if the fruit has been sprayed or has been picked up
off the ground.
Cut or slice fruit evenly so it dries all at
the same time. (Remove stones, pips, stems. Blemishes can very easily be
cut away, as long as an off flavour hasn’t developed through the fruit).
If there are uneven pieces allow for extra drying time for the thicker
parts.
Pretreatment : It is suggested that some
vegetables should be blanched prior to dehydrating to stop the enzyme
action that causes flavour loss. Fruit does not need any pre- treatment.
However, if you like to keep bananas and apples very pale they can be dipped
in lemon juice immediately after slicing (Conventionally, ascorbic or citric
acid are used as is sodium meta-bi-sulphite).
‘Too peel or not to peel’ that’s the question-
Entirely up to you!
Drying time will depend on temperature of weather
and dehydrator, humidity, thickness and moisture content of produce. Apples
sliced in approx 5mm slices might only take 8-10 hrs. Mulberries
left whole, 2-3 days. Generally it’s better to over-dry than under-dry.
To test for adequate dryness, let a piece of
produce cool, bend it and then squeeze it. If there is any moisture
showing the product is not dry enough and should be further dried so moulds
don’t develop during storage.
Storage in a cool and dark place. Use clean glass
jars or food grade plastic buckets with good fitting lids. If you are dealing
in very large quantities, cherry barrels (200 l) are excellent; they keep
moisture and dried fruit moths out. Even though you might not have seen
any moths, the eggs may already have been laid and hatch after you have
put the fruit in storage. Nothing is more devastating than to discover
hours and hours of work eaten away by these destructive creatures. So check
regularly for any sign of life. We use food grade carbon dioxide gas (available
from BOC Gases Ltd) to suffocate any living creatures in the storage containers
and to stop the development of any eggs laid (CO2 will also suffocate you
if used inappropriately so follow safety directions carefully). Freezing
will also kill most insect eggs.
It’s good policy to specifically check for moisture
after a few weeks - Was your product truly dry enough? Condensation in
the containers indicates it isn’t (or moisture is getting in). Moulds,
bacteria and fungi need to be treated with respect! Some are dangerous.
Also note that plastic containers may keep the
smell of previously stored food (eg pickles) for a long time and taint
the flavor of your new harvest.
Fruit Leathers: over ripe fruit can be stewed,
pureed and spread out on a lightly oiled sheet of plastic. Drying
times vary but are speeded up by turning the leather after a day.
Herbs can be dried. Temp should not exceed 35`C
Hygiene: Commonsense hygiene rules need to be
taken into account. Contact your local council Environmental Health Officer
for interesting and detailed information on Food and Hygiene.(Applicable
to home situation, compulsory reading if you are thinking of selling produce).
All the above information is easily used when you have an electric dehydrator.
Other methods of drying:
-
Sun drying: trays protected with cheesecloth to keep
insects off . Watch out for dew, rain, birds, rats and ants!
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Oven drying: care should be taken to not exceed 55-60`C-leave
door ajar- frequent turning helps drying
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Solar drying: Various driers are available - you
can also build your own
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Freeze drying: Generally not used in domestic situation.
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Refrigerated drying, using a special, new type of
machine.
Models available:
· DIY Fruit Dryer, Alternative Technology
Ass., 247 FlindersLane, Melbourne VIC 3000
· Jura Sol, Jura Heights, Gowan via Bathurst,
NSW 2795
· Solar Safe,RMB 2317 Euroa ,Vic 3666
· Ezidri (previously Harvest Maid),
Hillmark industries, 664 South Rd, Glandore SA 5037
ph 08 8371 1611 They also market the apple peeler
and corer.
· Nara, Shop 11, Albyn Tce, Strathalbyn,
SA 5255
· Sunbeam and other small dryers in local
stores
A wicked hint: orange dipped in chocolate
is simply delicious.
Useful books:
The Permaculture book of Ferment and Human Nutrition,
Bill Mollison, Tagari
Department of Agriculture Fact sheets on drying
fruit
Food Poisoning and Food Hygiene, Betty Hobbs,
Diane Roberts, publ. Edward Arnold
Drying Food, Ricky M, Gribling, Hyland House
Publishing
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