Fatgodzilla
Well-Known Member
Sorry to drag you all back to the botulism argument, but you are all missing one really important fact: the cubes used to store the wort are made of polyethylene, and polyethylene allows a lot of oxygen through it. So, once the wort is cooled, oxygen will to permeate the wall of the cube, dissolve in the wort, and the wort will become oxygen-saturated in a matter of days.
I did some math based on the oxygen transmission rates posted here - http://www.flextank.com.au/PDF_Files/2-Year-Update.pdf and came up with a transmission rate of about 2 ppm per day based on a full 20 liter cube, 27 cm on a side. So, in 4 days, enough oxygen could get in to saturate the wort. Voila, no spore growth since an anerobic environment is needed. I suspect the rate limiting factor is the diffusion of oxygen through the wort, not the permeation through the cube wall.
By the way, my calculations were based on a 1 mm (40 mil) wall thickness, and I suspect the cubes are less than half that, which increases the amount of oxygen that can permeate in 24 hours.
I surmise that no Aussie homebrewers have botulinized themselves for several reasons, none of which have to do with their robust immune systems... Presence of oxygen, sterilization of the wort by boiling, followed by natural pasteurization as the wort slow cools, and competition by yeast when a true anaerobic environment is created during the first phase of yeast growth.
I'm not sure why the cube use directions suggest minimizing air space, unless it is the originators of the idea didn't know about polyethylene's ability to transmit oxygen. Anyone know why? Fatgodzilla?
Here I am, dragged screaming back to the thread. Gone back to my sources on AHB for some REAL SIMPLE ANSWERS (cos we are homebrewers not scientists or chemists etc)
On the matter of oxygen satuation, the rates calculated may well be true for empty containers, but full containers of wort can't possibly allow that rate. While the container may allow the oxygen flow, what makes you think the wort will absorb it.
Australian reasoning .. fermenters are made with the same material as cubes. If this much oxygen was absorbable through the walls of a fermenter, why oxygenate prior to pitching yeast. Or the New Zealand reasoning .. you can lead a sheep to water, you can't make it drink.
The minimalisation of airspace is a "just in case" attitude. The less air in the cube, the less chance that there is anything in air that can harm you. I have done and others have done a no chill with a largish air head space with no problems - though in these cases I have brewed them asap. Aussie reasoning - you put a hot wort in a fermenter that is too hot to pitch the yeast, you close the lid and wait till the wort is cool enough. As a rule, nothing bad happens tp the wort, but the longer you don't pitch, the odds of problems happening increases. Particularly if you keep opening the lid.
I'm not sure why the cube use directions suggest minimizing air space, unless it is the originators of the idea didn't know about polyethylene's ability to transmit oxygen.
I won't tell them they can't be right if you don't !
More good old fashioned wisdom guys ..
Don't make mountains out of mole hills
If it walks like a duck, and quacks like a duck and has feathers like a duck, its probably a duck.
If it works, good. If it aint broke, don't fix it.
I'll let you blokes rabbit on about botulisma and oxygen permeability - no one has died of botullism due to no chilling and our worts stay fresh in the cube without going off for months. Why, I don't care ! It just does.
Go No Chill !!
Good brewing brothers !