# Killing Wild Yeast!



## Verbyla (31/5/09)

I know you can kill wild yeast by heating it up or adding chemical to pressed apple juice but i was wondering if freezing the juice would work just as well. I don't think i've heard it mentioned as a method of getting rid of wild yeast but i've read a few times to not allow yeast that you've bottled/harvest to get to freezing point. Apparently it kills the yeast by rupturing the cell membrane.

Is there any truth to what i've said and if so if it a good idea?


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## chappo1970 (31/5/09)

Personally I wouldn't rely on it as a method of killing things effectively. I would think it would be too hit and miss. I don't see laboratories employing freezing as a safe and effective means to destroy bacteria's and other nasty bugs. Heat is their weapon of choice, yeah?

Cheers

Chappo


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## Fourstar (31/5/09)

freezing doesnt kill bacteria.

App the thing todo is to add sodium met (campden tablet) to your apple juice. Some say it makes their juice sulfery.. others dont notice a thing. its widely used in making wine to kill bacteria and inhibit oxidisation. I think you also add more than 1 tablet per brew. I think its like 1 tablet per 4-5l. i dont know the ratio per L if you have it in powder form but i do know there is a ratio to it by weight. Do some research or maybe someone else has the correct info.

Cheers.


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## manticle (31/5/09)

Fourstar said:


> freezing doesnt kill bacteria.
> 
> App the thing todo is to add sodium met (campden tablet) to your apple juice. Some say it makes their juice sulfery.. others dont notice a thing. its widely used in making wine to kill bacteria and inhibit oxidisation. I think you also add more than 1 tablet per brew. I think its like 1 tablet per 4-5l. i dont know the ratio per L if you have it in powder form but i do know there is a ratio to it by weight. Do some research or maybe someone else has the correct info.
> 
> Cheers.



In my experience it's horrible during ferment and takes ages to clear once bottled. I can taste it in commercial ciders as well (the 'sulphuriness' lessens but an element of the sodium remains).

You can pasteurise your apples by putting them in water at 70-75 deg for a short time. Brewer Pete is probably the best person to ask about this and how it's done. There is a debate between people for and against pasteurised juice and how it can affect flavour and storage too but I reckon sulphur has no place near my apples.

Personally I'm an advocate for not worrying. If you make a starter then the chosen yeast should dominate and bacteria won't grow in the alcoholic environment as far as my small amount of reading suggests. I recently made a cider this way (clarified without yeast in a clean fermenter for 48 hours too) and it turned out fine. Any improvements needed had nothing to do with micro-organism spoilage.


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## pdilley (31/5/09)

Verbyla said:


> Is there any truth to what i've said and if so if it a good idea?



You need hydrated cells full of water to get some of them to start rupturing when frozen. What are you going to do for dried out yeast cells and wild spores?

Freezing is used for preserving in most cases.

Sterilisation is done in multiples of atmospheric pressures and lots of heat, steam is a good heat medium for an extended period of time... I just described a pressure cooker or its larger built brother, the autoclave. But then in brewing we do not aim for sterilisation we aim for sanitisation. 80/20 rule do the easy stuff 20% effort that gets rid of more than 80% of the problems and you let nature fend for itself. :icon_chickcheers: 

Freezing under controlled conditions is an alternative way how we preserve live yeast inside of frozen libraries for future use.

Cheers,
Brewer Pete

Work with nature :icon_cheers: not against it.


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