| Preservation of bio-degradables is an important | | | | destructive of tissue structure and leaves the dried |
| aspect. Traditionally Sun drying of pulses and some | | | | food with a woody texture formed due to ice |
| vegetables constituted preservation. Sunlight not only | | | | crystal growth during freeze drying. The leftover |
| removed maximum moisture but also its UV rays | | | | moisture leads to deterioration after a few years. |
| killed micro organisms facilitating longer shelf life. An | | | | Structural deterioration due to porous surface left |
| advantage of Sun drying is that the natural taste | | | | behind by ice crystals worsen the things. |
| would return upon reconstitution. | | | | However, these technical problems can be overcome |
| Air and water tight packing in polyethylene/PVC lined | | | | by common table sugar which inhibits ice crystal |
| aluminium foils and aluminium lined tetra packs provide | | | | growth as well as prevents denaturation. Brine |
| advanced protection from atmosphere. The sea | | | | shrimps, nematods, seeds are lyophilized(freeze dried) |
| food, meat, pulses etc. can be packed with natural | | | | in presence of sugars to prevent complete desication. |
| freshness. When stored in deep freezers, these | | | | Structural decay may be taken care off by chemical |
| would retain their natural freshness for longer periods. | | | | fixatives like formaldehyde and glutaraldehyde and |
| One aspect to note with such packing was that | | | | storing in oxygen in water tight and air tight |
| asceptic cleaning or sterilization was difficult in large | | | | containers. |
| scale production. | | | | The post production sterilization or autoclaving of |
| Food grains, in large quantities may be exposed to | | | | containers of injectables being not possible in most |
| nuclear(gamma) radiation which destroys micro | | | | cases, freeze drying comes to the rescue.The rise |
| organisms, germs and rodents. Bhaba Atomic | | | | and fall of temperature and pressure being absent in |
| Research Center in India has developed a technic for | | | | lyophilization, keeps the nature of fluids intact. The |
| exposing the food to such radiations. This is now in | | | | freeze dried products can be stored at room |
| effective use and is proven a boon for mass scale | | | | temperature. |
| storage and longer shelf life. | | | | The principle of freeze drying is sublimation. Meaning |
| However human organs, corpses or dead pets etc. | | | | that, under low pressure (0.06 atm) or vacuum, solid |
| were stored in cryogenic state (upto -180 degree | | | | water converts directly to gaseous form. |
| Celisus produced by LN2), a technique not suitable for | | | | The disadvantage with cryogenic preservation is the |
| vaccines. | | | | enormous cost over long periods. But liquid nitrogen |
| Freeze drying removes water content upto 98% | | | | (cryogenics) has its own advantage that it prevents |
| (depending on duration of freeze drying) while | | | | frozen tissues from suffering from other water and |
| retaining nature of ingredients. | | | | oxygen dependant deterioration. |
| The argument against freeze drying is that it is | | | | |