DEDICATED DRYING MACHINES MANUFACTURER
changes in their thermophysical properties. The rehydration kinetics, the structural properties (apparent
density, true density, specific volume and internal porosity), the viscoelastic behavior (compression
tests), and the flavor losses were the important parameters during rehydration of various fruits and
vegetables. The effect of temperature on the above properties are also impact on some fruits and
vegetables dehydrated by different drying methods (convective, vacuum, freeze, and osmotic drying).
The results showed that the water temperature influences the rehydration kinetics and the equilibrium
moisture content of the rehydrated. The structural properties of rehydrated foods appear to show a
hysteresis compared to those measured during dehydration processes. The shrinkage that takes place
during dehydration prevents rehydration and produces products with lower apparent density and higher
porosity. Structu ral damages that occur during drying seem to affect also the viscoelastic behavior of the
rehydrated foods and the hysteresis phenomenon is also impact on the textural properties, with a degree
varying between the different drying methods.
OUR DRYING SOLUTIONS
Convective drying: Convective method of drying is employed to remove water from the food substances
through the application of heat in equipment meant for drying. Hot air is allowed to pass through the
product in a manner to transfer the heat to the food and moisture is removed.
Vacuum drying is the mass transfer operation in which the moisture present in a substance usually wet
solid is removed by means of creating vacuum. In chemical process industries like food, pharmaceutical,
agricultural, textile, paper & pulp etc. drying is an essential unit operation to remove moisture. Vacuum
drying is generally used for the drying of those substances which are hygroscopic and heat sensitive and
is based on the principle of creating a vacuum to decrease the pressure below the vapor pressure of the
water. With the help of vacuum pumps, the pressure is reduced around the substance to be dried. This
decreases the boiling point of water inside that product and, thus, increases the rate of
evaporation significantly. The result is a significantly increased drying rate of the product. The pressure
maintained in vacuum drying is generally 0.0296 –0.059 atm and the boiling point of water is 25 -30 0 C.
The vacuum drying process is a batch operation which is performed at reduced pressures and lower
relative humidity compared to ambient pressure. That is why the drying occurs faster under these
conditions without oxidation.
Freeze-drying—technically known as lyophilisation, or cryodesiccation is a dehydration process
typically used to preserve a perishable material or make the material more convenient for transport.
Freeze-drying works by freezing the material and then reducing the surrounding pressure to allow the
frozen water in the material to sublimate directly from the solid phase to the gas phase.
OUR APPLICATION AND PRODUCT DEVELOPMENT SUPPORT
Dedicated Drying Solutions
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