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Select
Right Temperature
Food contains a
lot of water, therefore it is very important to select right
temperature
and drying method. Successful drying depends upon the removal of enough
moisture from the food to prevent spoilage and it must be done as fast
as possible at a temperature that does not seriously affect the
texture,
flavor and color of the food. Drying process should never be hurried by
raising the drying temperature. The optimum temperature for drying food
is 140ºF. For the first part of the drying process, the air
temperature
can be relatively high, that is, 150 to 160 degrees F (65 to 70 degrees
C), so that moisture can evaporate quickly from the food. Watch the
process
very carefully, and as soon as surface moisture is lost (the outside
begins
to feel dry), the air temperature must then be reduced to about 140
degrees
F (60 degrees C). For the best results use a thermometer to check the
oven
temperature to make sure it stays at 140 F. Check the temperature about
every half hour, because it is very important to keep the oven
temperature
at 140 degrees F.
If you use higher
temperatures to long the food will cook instead of drying. If the food
cooks on the outside and the moisture cannot escape the food may harden
on the surface and the food will eventually mold.
If the temperature
is too low at the beginning, the food may undergo undesirable micro
biological
changes before it dries adequately.
Keep in mind that
heat is not the same in all parts of the oven or dryer and stirring the
pieces of food frequently and shifting the racks in the oven or dryer
are
essential for uniform drying.
To speed the drying
process you can increase only the air flow (not temperature).
Remember
Lighter load dries
faster than a full load. Keep in mind that some food needs to be turned
over occasionally for successful drying. Stirring occasionally prevent
foods from sticking to the trays and also helps the food to dry evenly.
It is very important
to watch whole drying process carefully, because toward the end of the
drying process the food can scorch easily (each fruit and vegetable has
a critical temperature above which a scorched taste develops).
Note:
Never
use the broiler
unit of an electric oven because the food on the top tray will dry too
quickly. The best solution for oven drying is a proper model of
convection
oven that has a timer and controllable temperature starting at 120
degrees
F.
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Did You Know?
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It
is good idea to
keep the oven door open (for electric oven 5 to 6 inches, for gas oven
2 to 3 inches) during drying for ventilation. A block of wood (or
something
else) will help to keep the door open so that moist air can escape
while
the heat stays in the oven.
If
your oven do not
have a fan, you can place an electric fan in front of the oven door, it
will help to keep the air circulating. Be careful because this is not a
safe practice for a home with small children.
In
general, do not
attempt to dry food on rainy days when the relative humidity is high.
The
drying process will take much longer than on low humidity days. Humid
air
blown across the food contains more water vapor than dry air, so the
humid
air cannot hold as much of the water being removed from the food.
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