Published on Jan 10, 2016
We all know that food is a basic need for our living and now a day we often hear and observe famine all around the world. The word famine in the above sentence means low production of hygienically produced foods and vitamin foods .we all know that it is useful to build and maintain our body and provide them useful vitamin and carbohydrates etc.
Retail presentation of preserved foodstuffs is an ancient art. Freeze drying is a modern method, which has come in to the role for preserving food. Freeze drying in general is a process of freezing the foodstuff and then drying it to get rid off the moisture. In this process drying means changing of ice in to vapor without being melted and further that atmospheric pressure must be vaccumised in special machines, all of which makes the process slow, elaborate and somewhat expensive, but the resultant quality, the water is restored perhaps many years later, makes it all worthwhile.
Freeze-drying, or lyophilization, is like "suspended animation" for food. You can store a freeze-dried meal for years and years, and then, when you're finally ready to eat it, you can completely revitalize it with a little hot water. Even after all those years, the taste and texture will be pretty much the same.
In this article, we'll explore the basic idea behind freeze-drying, and we'll look at the different steps involved in the process. We'll also see how freeze-drying is different from ordinary dehydration, and we'll find out about some of its important applications.
The basic idea of freeze-drying is to completely remove water from some material, such as food, while leaving the basic structure and composition of the material intact. There are two reasons someone might want to do this with food.
Removing water keeps food from spoiling for a long period of time. Food spoils when microorganisms, such as bacteria, feed on the matter and decompose it. Bacteria may release chemicals that cause disease, or they may just release chemicals that make food taste bad. Additionally, naturally occurring enzymes in food can react with oxygen to cause spoiling and ripening.
Like people, microorganisms need water to survive, so if you remove water from food, it won't spoil. Enzymes also need water to react with food, so dehydrating food will also stop ripening.
Lyophilization, commonly referred to as freeze drying, is the process of removing water from a product by sublimation and desorption. This process is performed in lyophilization equipment which consists of a drying chamber with temperature controlled shelves, a condenser to trap water removed from the product, a cooling system to supply refrigerant to the shelves and condenser, and a vacuum system to reduce the pressure in the chamber and condenser to facilitate the drying process.
Lyophilizers can be supplied in a wide variety of sizes and configurations and can be equipped with options that allow system controls to range from fully manual to completely automated. For pharmaceutical compounds that undergo hydraulic degradation, lyophilization offers a means of improving their stability and shelf life. Many parenteral medications such as vaccines, proteins, peptides, and antibiotics have been successfully lyophilized. New biotechnology products will also increase the demand for freeze drying equipment and processes.
A typical machine consists of a freeze-drying chamber with several shelves attached to heating units, a freezing coil connected to a refrigerator compressor, and a vacuum pump.
With most machines, you place the material to be preserved onto the shelves when it is still unfrozen. When you seal the chamber and begin the process, the machine runs the compressors to lower the temperature in the chamber. The material is frozen solid, which separates the water from everything around it, on a molecular level, even though the water is still present.
Next, the machine turns on the vacuum pump to force air out of the chamber, lowering the atmospheric pressure below .06 ATM. The heating units apply a small amount of heat to the shelves, causing the ice to change phase. Since the pressure is so low, the ice turns directly into water vapor. The water vapor flows out of the freeze-drying chamber, past the freezing coil. The water vapor condenses onto the freezing coil in solid ice form, in the same way water condenses as frost on a cold day.
This process is much cheaper for pharmaceuticals. Cost mainly depends on engineering skills and techniques. The quality of the products is very high.