DIY Homebrewing Yeast Freezer

[mvanwie]

Apparently, at lab-grade freezer temperatures (-22F/-30C), yeast in a glycol solution will survive almost indefinitely. At normal freezer temperatures (-10F to 5F), the expectations I've seen are anywhere from 3-10 years, which presumably depends upon the storage temperature. I'm interested in starting a yeast farming operation (for my own purposes, not commercially), and like most things I do, I'm going for complete overkill (just to see if I can). So I was hoping to hit something as close to lab-grade as I could with materials I have lying around (or can pick up cheap), but since my HVAC knowledge is quite limited, I'm looking for some advice. Basically, the plan is to take an old mini-fridge and simply remove the chamber, leaving the refrigerant loop (compressor, condenser, evaporator) behind and completely intact. I would then build a new chamber around the refrigerant loop that would 1) open to the top, 2) be highly insulated, and 3) be liquid-tight. The chamber would be filled with denatured alcohol and the evaporator would be submersed into the liquid. Vials of yeast in glycol would then be stored also by submersion in the liquid.

I'm wondering what I'm overlooking with the refrigeration operation/theory above, specifically:

1) Is the theoretical "minimum" temperature of the evaporator the boiling point of R-134a (or other refrigerant) adjusted according to the low side pressure?

2) Does the ambient temperature affect the pressure inside the evaporator or is temperature strictly the result of the pressure?

3) Could you refrigerate to the point where low side pressure became negative and thus lower the evaporating temperature of the refrigerant?

Since R-134a boils at -15F/-26C, I was thinking it should be possible to at least get the alcohol bath down to -4F/-20C if I insulate the **** out of it, which I'm hoping would keep my yeast alive as long as I plan to be home-brewing.

Any input is appreciated.

 

[broadbill]

The problem I see is that you could go through this whole operation and end up with a perfectly function chiller/freezer, but it still might not get cold enough.

For the number of hours you are going to pour into this project is substantial, wouldn't it be easier to just replate/reculture every few years?

 

[BBL_Brewer]

The problem I see is that you could go through this whole operation and end up with a perfectly function chiller/freezer, but it still might not get cold enough.

For the number of hours you are going to pour into this project is substantial, wouldn't it be easier to just replate/reculture every few years?

I sort of have to agree with broadbill. If you reculture every year or two, you can maintain an ample supply of yeast to brew with. I do the same thing myself and store my yeast at the bottom of a chest freezer. However, I'm interested in seeing if there are ways to achieve colder storage on the home level without buying a commercial -80 unit. Keep the creative thoughts flowing and let us know what you come up with.

 

[mvanwie]

The problem I see is that you could go through this whole operation and end up with a perfectly function chiller/freezer, but it still might not get cold enough.

For the number of hours you are going to pour into this project is substantial, wouldn't it be easier to just replate/reculture every few years?

Perhaps, but isn't the purpose of a hobby to waste time and money, not save it?

In all seriousness, you're absolutely right, hence the reason I'm asking questions... I simply want to know beforehand whether I need to design the freezer with an adaptive use (maybe a second primary chamber... who knows) should it not get cold enough.

 

[Sebas83]

Hobbies are also there to help maintain sanity, not exacerbate insanity

Seriously though, if you want to try, by all means, do it. But, of the effort is to maintain a functional yeast library for personal use, I would consider the yeasts you love to use, ones that are great but are used infrequently, or cultured yeasts (wild, from bottles from far off lands, etc) and maintain that and use the yeasts regularly and replate every year or so.

Keeping a scientifically sound freezer AND a library is not only difficult to create, but difficult to maintain. Also, if you are making it, consider what would happen if it breaks down. It would SUCK to have this large archive of yeasts and have it break and not call in your warranty

Not to dampen the DIY mentality, but there are some things other people and companies do, and have done, really well. I think low temp refrigeration is one. BUT if you have the engineering chops to pull it off, do it!! You might end up with a patent and a product to sell to other brewers who want a small yeast freezer.

 

[ChuckO]

What about using a Peltier Diode cooler placed inside a deep freeze? Peltier coolers can cool to 40 deg. below ambient. If ambient is below zero in a deep freeze it might be possible.

 

[mvanwie]

What about using a Peltier Diode cooler placed inside a deep freeze? Peltier coolers can cool to 40 deg. below ambient. If ambient is below zero in a deep freeze it might be possible.

Not a bad idea... if you can keep a deep freeze at -10F, -22F doesn't seem all that difficult if the cooler is well insulated. I'm not entirely familiar with Peltier operation, but I do know that they're very inefficient and take a long time to cool down, so unless you kept a lot of mass in them, one lift of the lid and you might be right back to -10F inside the cooler. That's assuming they're not liquid tight, which is one of the more critical components of my design; the alcohol bath maintains a constant temperature... which would allow me to open the -5F chamber in a 70F room and not have to worry about my stock rising several degrees. Even in a chest freezer, the air temp can swing a few degrees every time you open it. The impression I get is that maintaining a constant temperature is just as important as the storage temperature itself when it comes to long-term storage & viability.

 

[ChuckO]

The Peltier cooler that I have is built just like an ice chest without a drain hole. The diodes and fan are mounted in a removable lid, so the chest is water tight. Denatured alcohol might be a problem with the plastic though. I think that I might test this over the winter by putting the cooler outside this winter and recording the temperature in it.

What about filling the extra air space with artificial ice packs? They might also help keep things cold during a power failure.