Dehydration process, Typically used to preserve a perishable material or make the material more convenient for transport, Mostly used for light food required by astronauts, hikers

1. Freeze Drying
New preservation technology

2. TD 611
 Also known as lyophilisation,
lyophilization, or cryodesiccation
 “lyophilization” – process for a product
that “loves the dry state”
 Dehydration process
 Typically used to preserve a
perishable material or make the
material more convenient for transport
 Frozen water is sublimated to vapor
phase
Freeze Drying

3. TD 611
Nearly every food can be freeze -dried
Astronauts’ and hikers’ food

4. TD 611
Phase Diagram
of water
Pressure
Temperature
Vapor Pressure
(mbar)
Temperature
(C)
6.104 0
2.599 -10
1.034 -20
0.381 -30
0.129 -40
0.036 -50
0.011 -60
0.0025 -70
0.0005 -80
Pressure-Temperature
for sublimation

5. TD 611
Food is pre-treated, flash
frozen &
Placed in a vacuum chamber
About 90% of the food’s
moisture is drawn off by
evaporating the ice of
temperatures as low as -50 C
Water replaced,
Original flavor, aroma,
texture, and appearance
Freeze – dried food sealed in
moisture + Oxygen proof
packaging to ensure freshness
I
II
IIIIV

6. TD 611
Compressor
Door
Heated shelves Refrigeration coils Cooling coils

7. TD 611
• Method of treating the product prior to freezing Eg. Conc. the product, formulation
revision
Pre-treatment
• Cool the material below its triple point (Complex process)
• Larger crystals are easier to freeze-dry, so slow cooling good (in certain materials)
Freezing
• Lowering of Pressure (to the range of a few millibars)
• Sublimation by supplying heat
• Re-solidification of moisture on Condenser
Primary Drying
• Temp. raised to break physico-chemical interactions remove unfrozen water
• Pressure is also lowered in this stage to encourage desorption
• Vacuum is usually broken with an inert gas
Secondary Drying

8. TD 611
Vacuum Pump
Condenser Plate
HeatingPlates
HeatingPlates
Moving
Sublimation
front
Frozen vapors
PRODUCT
Frozen
Dried

9. TD 611
Pressure -Temp variation during the processMoving Sublimation front

10. TD 611
Industrial freeze dryers
Home freeze dryers
Cost of a small home freeze dryer ~ 4-5 lakhs INR

11. TD 611
Heat Transfer
Driving Potential - temp. difference
𝑞 =
−𝐾𝐴
∆𝑥
(𝑇𝑠𝑢𝑏−𝑇𝑓)
Mass Transfer
Driving Potential - Pressure difference
𝑚 =
𝑘 𝑑 𝐴
∆𝑥
(𝑃𝑠𝑢𝑏−𝑃𝑐𝑜𝑛𝑑) = 𝜌𝐴
𝑑 (∆𝑥)
𝑑𝑡
Coupling of heat and mass transfer
𝑞 = 𝑚 𝐿
** Valid undersuitable assumptions
𝑃𝑐𝑜𝑛𝑑 = 𝑃𝑠𝑢𝑏 +
𝑘
𝑘 𝑑 𝐿
(𝑇𝑓 − 𝑇𝑠𝑢𝑏
Frozen Layer
Dried Layer
Plate heater
L
∆𝑥
Tsub, Psub
Tf, Pcond

12. TD 611
Preservation of temperature sensitive products
Biological origin materials, eg. Blood plasma, enzymes, vaccines etc.
Health friendly
No preservatives, GMO free, Gluten free, Vegetarian and vegan
Almost all food products can be freeze-dried
Fruits, vegetables, meat, pharmaceuticals, ice-cream, sandwich… anything
High Stability (for several years)
Once packed properly, long shelf life at ambient conditions for years
Preserves the natural color, taste and appearance
No damage to the natural properties of the product

13. TD 611
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