The most used method to increase shelf life
Just as food can spoil, also laboratory reagents and samples can spoil. Cooling is the most used method to increase shelf life by slowing down the metabolic activity of samples and spoiling micro-organisms. In general, we can say the lower the storage temperature, the more the metabolic activity slows down and the longer the shelf life. For longer term storage, also the ice structure is important. Water freezes at approx. 0°C and forms hexagonal crystals. Below the first re-crystallization point at approx. -80°C, the crystals become cubic, and the metabolic activity drops down significantly. Below the second re-crystallization point at approx. -130°C, the ice goes to amorphous structure and the metabolic activity shuts down completely.
What cooling instrument is needed for my sample storage?
Depends of the sample type and how long you want to store it. General guiline:
- Refrigerator: 4°C: storage for days - weeks
- Freezer: 0 to -20°C: short term storage: weeks – months
- Freezer (expended temperature range): -20°C to -50°C: mid-long term storage: months – years
- Ultrafreezer: -80°C: long term storage: years
- Cryofreezer: <-135ºC: Very long term storage (Infinite time)