freeze drying process

2. Introduction
•Lyophilization or freeze drying is a process in which water is frozen,
followed by its removal from the sample, initially by sublimation (primary
drying) and then by desorption (secondary drying).
•Freezedrying is a process of drying in which water is sublimed from the
product after it is frozen.
•It is a drying process applicable to manufacture of certain pharmaceuticals
and foods that are thermolabile or otherwise unstable in aqueous solutions
for prolonged storage periods, but that are stable in the dry state.
•The term “lyophilization” describes a process to produce a product that
“loves the dry state”
•In the 15th century, freeze drying was used by the Incas. They stored their
crops on the mountain heights above Machu Picchu where the cold
mountain temperatures froze the food and the water inside slowly
vaporized under the low air pressure of the high altitudes.
•Nestle was first introduced freeze dried instant coffee in 1938 April
•Future use PROMESSION (Promession is an environmentally friendly way
to dispose of human remains by way of freeze drying)

3. Theoretical Basis of Freeze Drying
• At the triple point (0.0098°C and
4.58 mm Hg), ice , water and
water vapor coexist in
equilibrium..
• If we heat the water above the
triple point, the water will change
from liquid state to vapour state
• But when we heat the water
below this triple point, then the
water will change from solid state
to vapour state directly
• Conversion of ice into water
vapour is called as sublimation
• It is the basic principle of freeze
drying process

4. Stages in the Freeze-Drying Process:
1. Pre-freezing
2. Primary drying
3. Secondary drying:

5. 1)Pre freezing:
Material intended to be freeze dried must first be pre frozen below its
eutectic temperature. The minimum freezing point attainable
corresponding to the eutectic mixture known as eutectic point.
After prefreezing the product, conditions must be established in which
ice can be removed from the product via sublimation. This requires
very careful control of two parameters: temperature and pressure. The
rate of sublimation of ice from a frozen product depends upon the
difference in vapor pressure of the product compared to the vapor
pressure of the ice collector. Molecules migrate from the higher
pressure sample to the lower pressure sample. Since vapor pressure is
related to temperature, it is also necessary that the product
temperature is warmer than the ice trap temperature.
2)Primary drying:
3)Secondary drying:
After primary drying is complete, all ice has sublimed but bound
water is still present in theproduct. Continued drying is necessary at
warmer temperatures to remove the residual water. This process is
called isothermal desorption as the bound water is desorbed from the
sample. During secondary drying, the product temperature is higher
than ambient. All of the other conditions, such as pressure and ice
trap temperature remain the same.

6. •Since all the moisture is removed from the food, its weight decreases making it
easier to carry or transport.
•All the nutrients and flavors are retained when food is freeze dried. Even the aroma
is not lost.
•The food does not shrink or its texture does not change when it is freeze dried. This
makes it a better option than dehydration.
•Since, the ice sublimes, it leaves small pockets in food. Thus, when the food is
reheated, it hydrates evenly all over. It takes only 10 minutes to rehydrate.
•It has a very long shelf life and can be quickly rehydrate as well. This makes it ideal
for backpackers or hikers to carry.
•Freeze-dried foods can stay edible for up to 25 years if unopened. Fruits or ice
creams can be eaten without hydrating them. This makes it a very convenient food
option.
Advantages :

7. The biggest disadvantage of freeze-drying is its cost. It is extremely costly, and
may not be cost-effective for certain foods.
Not all foods can be freeze dried, some may get spoiled when freeze dried; others
may need pretreatment to retain color or flavor.
Additives may be used when freeze-drying food.
Canning or dehydration is cost-efficient compared to freeze-drying.
Along with the water, other liquids like vinegar can sublimate, leading to spoilage
of food or change in taste in some cases.
Airtight and moisture-control storage is absolutely necessary to ensure that the
food does not spoil. Even slight exposure to humidity can easily spoil the food.
Disadvantages

8. Industrial Freeze Dryers:
2)Tunnel Freeze :
Dryer This process consists of trays being loaded into the freeze dryer at one end and dried
product being discharged from the other end. The process takes place in a large vacuum
cabinet, and the trays are loaded and unloaded through vapor locks. The dryer is divided into
five independent processing areas. It is cooled by an aqua-ammonia absorption refrigerator
which can control the load more readily. This type of freeze dryer is advantageous because the
flowrate can be increased as demand increases, although it is difficult to switch from one
product to another.
1)Tray Freeze Dryer :
The most common type of freeze dryer in operation is the tray freeze dryer. The condensers are
mounted in the same chamber as the tray-heater assembly or in a separate chamber joined by a
wide tube. The size of these dryers range from 120 to 220 ft2 and the product rests on trays
within the drying chamber. If the required capacity of the dryer is great enough, several freeze
dryers may be operated from a central tray heater, condenser, refrigeration, and vacuum pump
system. The system would be programmed to stagger the dryer cycles and even out the load on
each part of the system. Each dryer could be individually controlled by its own panel, yet the
operation would be semicontinuous

9. Freeze drying equipment suppliers:
National
SSP INDIA http://www.sspindia.com/
SUBZERO INDIA http://www.subzeroindia.in/
LABSOL http://www.labsol.co.in/
BIOLINE TECHNOLOGIES http://www.biolinetechnologies.com/
Inter national
GEA http://www.gea.com/en/productgroups/dryers_particle-processing-
systems/freeze-dryers/index.jsp
ZIRBUS http://www.millrocktech.com/freeze-dryers/
MILLIROCK TECH http://www.zirbus.com/freeze-dryer/production-units/
HUDSONVALLEYLYOMAC http://www.hudsonvalleylyomac.com/industrial-freeze-
dryer.html
MARTINCHRIST https://www.martinchrist.de/en/products/production.html

10. THANK YOU