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SPECIAL FOCUS
SPECIAL FOCUS

Nature of Thawing
When freezing is removing heat from food to form ice,
thawing is heating of food to defrost the ice. Both processes
are reversed in terms of giving and pulling heat, but rather
different in terms of heat transfer between water and ice.
Therefore, the relationship between food temperature and
time of operation so called Freezing curve and Thawing
curve is different.
How to Properly Thaw Frozen Foods

Ice has properties to conduct heat (thermal conductivity) 4 times the inside, the surface temperature is usually slightly lower (0.2-1°C).
better than water and 9 times better than water on a heat dissipation However, defrosting by microwave may also cause unevenness
(thermal diffusivity). Hence, when defrosting food by surface heating, (non-uniformity) of food inside. This causes a localized heating
it causes movement of water in the food tissues (non-convection of pocket, which can affect the quality of food.
water in tissue). The ice crystal then transmits the heat that changes In short, the proper way to thaw frozen foods is fast thawing,
the temperature faster than water (stay still). We, therefore, can see but considers not to over-temperature that the microorganisms can
the food surface melting at a fast rate. When the surface gets grow quickly on the surface or inside of the food.
dissolved, the water slows down the transmission and the This problem will be eliminated if consumers cook with the
temperature of the food, allowing it to take longer to thaw before temperature high enough to destroy the microorganisms and finish
passing latent heat to the ice. That is why defrosting takes a long all of those food.
time. Often notice that the food looks well thawed outside, but once Fast thawing provides better quality food than slow thawing.
have it cut, the center remains frozen. Slow thawing causes a large amount of water loss from food.
Because recrystallize often destroys the cell wall. This is one of the
Appropriate Thawing Method reasons why the food tissue cannot reabsorb the drip. The drip loss
When defrosting by heat transmission from the surface takes a long of frozen food causes undesirable color, taste, nutritional value, and
time, the internal heating becomes another option that saves a lot texture of the foods. The drip or thaw exudate depends on such
of time. This is why a microwave oven has brought into use to thaw factors like food structure, chemical change, bio and physical
frozen foods. chemistry of food, including freezing method, frozen storage, and
The way in which the microwave is used is to induce thawing.
electromagnetic waves directly into the food to heat molecules of
water and food. With dielectric heating, the molecules of ice inside Quality of Food after Thawing
and at the food surface are simultaneously activated. Thawing then As a manufacturer, what should be
happens faster and more complete. Combining with the heat on the concerned on thawing is suitability of
food surface which is transmitted to the surrounding air easier than time and temperature. Fast thawing

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