Liquid nitrogen is nitrogen in a liquid state at an extremely low temperature. It is a colourless clear liquid with a density of 0.807 g/ml at its boiling point (−195.79 °C (77 K; −320 °F)) and a dielectric constant of 1.43.. It is produced industrially by fractional distillation of liquid air. Cryogenic freezing is most often used for individual quick frozen (IQF) products, such as individual chicken wings, frozen peas, or other bulk packaged food items where it is important to maintain individual pieces.It is sometimes chosen where space is limited or as a lower-cost means of getting a new product to market quickly.

Cryogenic nitrogen plant. Air inside a distillation column is separated at cryogenic temperatures (about 100K/-173°C) to produce high purity nitrogen with 1ppm of impurities. The process is based on the air separation. This method involves a standard mechanical refrigeration cycle, using one of the common refrigerants like ammonia or carbon dioxide. Mechanical process freezing systems usually have higher capital costs than cryogenic systems because they require supporting refrigeration systems. But, they’re usually the more efficient and cost-effective option from a long-term standpoint. Mechanical freezing is most often used for high-volume production of both raw and finished goods.

Freezing with Cryogenic Liquids

Liquid nitrogen (or other cryogens or liquid carbon dioxide) freezing has many advantages over mechanical freezing and chilling processes:

1. Faster

2. Colder

3. More flexible

4. Takes up less space

5. Lower maintenance

Cryogenic freezing also helps minimize dehydration of the frozen items, while retaining item quality, texture, color, and, in the case of food items, flavor.

I endorse Prem Baboo

I used both LN and cryo-freezers over a period of 20 years and found the mechanical freezers to be the best option, especially if you have lots of samples to store. I have had 5 freezers running with hundreds of thousands of cryovials stored. The mechanical freezers are reliable (and you don't really need any LN backup for them), they are much safer (LN vapour buildup in rooms with lots of tanks has caused at least one death that I know of), and you don't have the hassle of all the plumbing required for LN use. Both LN and mechanical freezers require some occasional defrosting due to ice buildup inside them caused by opening and shutting to input/remove samples. I found this easier to deal with in the mechanical freezers, as the LN tanks and their vapours can be deadly if the vapours have not fully dispersed before you start trying to clean the tank.

I should note that my positive experience with mechanical ultra-low temp freezers has been with -140C and -135C models - both of which are suitable for long-term storage of cultures and which we have used for storage of bacteria, actinomycetes and fungi for many years. I would not recommend -80C freezers for long-term storage of microbial cultures, but they may be suitable for storage of molecular material.

Many thanks to you all!

Our lab uses both LN and ultra-low freezers. We use the LN for longer-term storage and the freezers for frequent access.

I think ABM has a good deal ongoing for their ultra-low freezers. You can try asking them (https://www.abmgood.com/lab-equipment/lab-freezer/Ultra-Low-Temperature-Lab-Freezer-528-L-Q5126.html)

Liquid nitrogen is the optimal way

There is a small comparision done here on this link...

https://www.labmanager.com/how-it-works/2017/02/how-an-upright-liquid-nitrogen-freezer-works#.XaiYIOhKhaQ

Dear dr. Anna Git

Very nice and attractive discussion

Best regards

Dear dr. Vimal Keerthi

Nice contributions

Best regards

Dear Dr. Leo Urmaza

Good Contribution

Best regards

Hi at all!

A lot of the given answers were referring to LN2 vs.-80°C. But what about mechanical freezer reaching -150°C? These devices are meant to be alternatives to liquid nitrogen storage. Any experiences here?

Here an example: https://www.phchd.com/eu/biomedical/preservation/ultra-low-freezers/Cryogenic-ULT-freezers/mdf-c2156van

Thank you!

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