DEDICATED FOOD DRYING MACHINES MANUFACTURER

1. Dedicated Food
Drying Machines
Manufacturer
KDM Analytical
B-2/41, First Floor
Rohini Sector-16, Delhi – 110089
E-Mail: saleskdmanalytical@gmail.com , Phone: +91-9643480893

2. PRODUCT CATALOGUE

3. KEY OF SUCCESS

4. OUR DEDICATED FOOD DRYING SOLUTIONS
HOT AIR FOOD DEHYDRATOR

5. INDUSTRIAL FOOD VACUUM
DRYER

6. FOOD FREEZE DRYER

7. OUR HIGH TECH FABRICATION

8. DRYING KINETICS

9. MOISTURE CONTENT

10. • Drying (dehydrating) food is one of the oldest and easiest
methods of food preservation. Dehydration is the process of
removing water or moisture from a food product. Removing
moisture from foods makes them smaller and lighter.
• Dehydrated foods are ideal for backpacking, hiking, and
camping because they weigh much less than their non-dried
counterparts and do not require refrigeration. Drying food is
also a way of preserving seasonal foods for later use.
• Foods can be spoiled by food microorganisms or through
enzymatic reactions within the food. Bacteria, yeast, and
molds must have a sufficient amount of moisture around them
to grow and cause spoilage. Reducing the moisture content of
food prevents the growth of these spoilage-causing
microorganisms and slows down enzymatic reactions that take
place within food. The combination of these events helps to
prevent spoilage in dried food.

11. • The preservation of foods by drying is based on the fact that
microorganisms and enzymes need water in order to be active. In
preserving foods by this method, one seeks to lower the moisture
content to a point where the activities of food-spoilage and food-
poisoning microorganisms are inhibited. Dried, desiccated, or low-
moisture (LM) foods are those that generally do not contain more
than 25% moisture and have a water activity (aw) between 0.00
and 0.60. These are the traditional dried foods. Freeze-dried
foods are also in this category. Another category of shelf-stable
foods are those that contain between 15% and 50% moisture and
an aw between 0.60 and 0.85.
• These are the intermediate-moisture (IM) foods. Dehydrated
products readily take up moisture when immersed in a liquid
medium, leading to significant 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

12. • 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. Structural 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.

13. • 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.

14. • 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.

17. Rehydration of Dehydrated
Foods

18. • Dehydrated products readily take up moisture when immersed in a
liquid medium, leading to significant 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 taken care during
rehydration of various fruits and vegetables. The effect of
temperature on the above properties is also important for some
fruits and vegetables dehydrated by different drying methods
(Convective i.e Hot Air Drying, Vacuum Drying, Freeze Drying, and
Osmotic Drying).
• 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. Structural damages that occur during
drying seem to affect also the viscoelastic behavior of the
rehydrated foods and the hysteresis phenomenon is also observed
at the textural properties, with a degree varying between the
different drying methods. These kinetics define product quality.

20. ATMOSPHERIC HOT AIR DRYING

21. • Drying of any food products play an important role so far quality
of the dehydrated products are concerned. Normally dehydration
of food products are carried out by removing of moisture from the
surface and core of the product. In case of surface drying, most of
the moisture's are removed from the products safely without much
degradation of the product quality, so far nutritional value, color,
aroma, texture, structure and rehydration kinetics are concerned.
The removal of moisture from the core is very critical and requires
special thermal treatment for dehydration, so that the product
quality can be maintained along with their rehydration kinetics.
• There are several drying techniques available
• Hot Air Drying / Vacuum Drying / Freeze Drying / Combination
Drying etc.
• Referring to the tables, the boiling point of water under normal
atmospheric pressure i.e at 760 Torr is 100 0
C. The food materials
contain water in the form of moisture and during removing
moisture, we are using various techniques like Hot Air Drying,
Vacuum Drying, Freeze Drying etc by maintaining water activity in
the range of 0 to 0.6.

22. • HOT AIR DRYING is most suitable and economical drying technique
to remove moisture from the surface of the product by
maintaining color, texture, aroma, structure, nutritional value etc
upto the residual moisture content in the range of 20 to 25 %
safely within the product without degradation. For removal of
core moisture combinational drying technique is more effective so
far product quality is concerned. Shelf life of the dehydrated
products is depending on residual moisture and water activity.

23. VACUUM FOOD DRYING
TECHNIQUE

24. • The use of vacuum combined with heat can be an effective method
for drying. Lower moisture content can be achieved when using a
combination of vacuum and heat compared to heat alone
(particularly with products that are porous or have a very high
surface area). The use of vacuum drying has shown further
improvement in quality of food products. It reduces thermal stress
and sustains better colour and texture of dried products compared
to those that were air-dried. Rehydration kinetics is quite good.
• A vacuum drying system consists of the vacuum chamber and
source of the heat. Both oil-sealed and oil-free (dry) mechanical
vacuum pumps can be used. A condensate trap (typically cooled to
very low temperatures) is also used to pump and trap the liquid(s)
to be removed. Base pressures of less than 0.1 Torr (1,333 × 10-4
bar) are often required, depending on the liquid to be removed
and the temperatures which we want to achieve. Care should be
taken to protect oil-sealed pumps from the liquid and operating
the pumps properly to minimize the impact of the liquid vapours
being ingested into the pump (often with the use of a gas ballast
and/or gas purge).

25. • The vacuum drying process often involves multiple steps of
applying heat and vacuum. Reducing the pressure (applying
vacuum) at the surface of a liquid (such as water) will allow the
liquid to evaporate without elevating the temperature. The
evaporation of the liquid will continue until the product is dried
or until enough heat is removed (through evaporation) that the
remaining liquid freezes. At this point the drying process continues
as sublimation which is much slower compared to evaporation. In
general, this is not desirable. The purpose of heat is to maximize
drying while preventing freezing of the liquid. There are several
methods of applying heat to the product being dried. Some
products have temperature limitations which may impact the
methods that may be employed.
• These methods include:
• Preheating the product using a variety of methods prior to placing
into the vacuum chamber.
• Preheating the product in a specially designed vacuum chamber
that is configured to provide convection heating.

26. • Heating the walls of the vacuum chamber.
• Heating the shelves inside the vacuum chamber. This technique
can apply heat directly to the product by contact to the shelf.
• Flowing hot gas, such as nitrogen, into the chamber. This can be
done using a variety of techniques.
• Using infrared heating sources - vacuum infrared drying . This non-
contact method can be an effective and costly method of
transferring heat to a product under vacuum .
• Using microwave heating sources. This technology is advantageous
for bulk products with poor thermal conductivity. The microwave
vacuum technology is used for high-end drying applications of
thermal sensitive products like fruits and vegetables in order to
achieve higher product qualities and shorter drying times.
Microwave drying is more convenience in compared to conventional
drying methods and it offers many kinds of advantages. This
technology is suitable for a wide spectrum of food e.g.
strawberries, cranberries, banana, carrot, honey, mushrooms etc.

27. • Vacuum drying of food products is an unique solution as the
boiling point of water act as a negative coefficient of atmospheric
temperature i.e at lower atmospheric pressure boiling point of
water reduced,and residual moisture 1 to 3% can be achieved
safely without product degradation and this is the only reason why
vacuum drying can able to retain high nutritional value, color,
aroma, texture, structure etc.

28. BASIC PRINCIPAL OF FREEZE
DRYING

29. • Freeze Drying is carried out using a simple principle of physics
sublimation. Sublimation is the transition of a substance from the
solid to the vapour state, without first passing through an
intermediate liquid phase. Freeze Drying is performed at
temperature and pressure conditions below the triple point, to
enable sublimation of ice. The entire process is performed at low
temperature and pressure by applying vacuum, hence is suited for
drying of thermolabile compounds. The concentration gradient of
water vapour between the drying front and condenser is the
driving force for removal of water during Freeze Drying.
• Basic components of a Freeze dryer
• Construction and main components of freeze dryer: 1. Vessel,
shelves, trays and vapor condenser: 2. Refrigeration compressor 3.
Vacuum pump. Residual moisture in the range of 1-3% can be
achieved with high dehydration kinetics.

40. Thank You
KDM Analytical
B-2/41, First Floor
Rohini Sector-16
Delhi-110089, India
E-Mail: saleskdmanalytical@gmail.com
Phone: +91-9643480893