FOOD PROCESSING AND PRESERVATION
DRYING AND DEHYDRATION
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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The drying rate of food is constant.
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The water in the food constantly moves to the surface of the skin.
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The heat from the medium (hot air) received by the material is used to evaporate the water from the food.
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equilibrium moisture content
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Detailed explanation-1: -The moisture content at which the drying rate ceases to be constant is known as the critical moisture content. During the constant rate period, the moisture from interior migrates to the surface by various means and is vapourised. As the moisture content is lowered, the rate of migration to the surface is lowered.
Detailed explanation-2: -The moisture contents of solid when it is in equilibrium with given partial pressure of vapour in gas phase is called as equilibrium moisture content. Moisture content at which the constant rate drying period ends and the falling rate drying period starts is called critical moisture content.
Detailed explanation-3: -The e.m.c. is important as drying may be carried out unnecessarily resulting in a reduction in the capacity of a given drying system, a higher cost of drying, and an economic loss. The difference in e.m.c. values for a particular product are often due to variations in measuring techniques and grain varieties.