Yeast harvesting SNAFU

[bbslaw]

So for my last kit (St Peter's Golden Ale), I bought some S-04 yeast as I wanted a good floculator - sick of wasting beer due to floaty yeast packs. At £2.50 a pop, I wanted to try to get more than one use out of it, so having read a few threads on here, I 'dirty' harvested the trub by swirling it with a bit of remaining green beer and splitting between two sterilised jars. I've kept it in the fridge and my aim is to do a starter in the new year (to check it's viable) and then pitch in a cheap kit I've got (not taking the risk with a toucan at the moment). Being conscious of sterility I kept the lids tightened on the jars and occasionally let gas out when the tops looked swollen. However, last night I vented one of them and a few minutes later the yeast had rushed to the top of the jar leaving the beer below it - it almost looked like it was carbonated. Once I opened the lid again, there was no way to keep it in, and that jar had to go down the sink. So I have one jar left and my questions are, why did this happen? and should I keep the lid loose on the other jar?

 

[rpt]

I've always rinsed my yeast before storing it in the fridge so this would have got rid of any fermentable sugars and so I've not had a problem. I'd keep the lid loose, but you need to use the saved yeast soonish.

 

[bbslaw]

Thanks. So there might have been some fermentables left in the green beer then. The lid's loose now. What's the longest anybody's left yeast harvested in this way before successful use, and is a starter essential? Should I use yeast nutrient?

 

[graysalchemy]

I once kept some trub in a 2l pet for 2 -3 months in my naivety I thought the yeats would be keeped sterile as it was. The problem was trying to get the lid off. Even venting it resulted in brown yeasty whippy cream everywhere. Eventually I just opened upside down in an FV. The beer went off like a rocket (we have all seen the pictures). :whistle: :whistle:

 

[bbslaw]

Not sure I understand - was it successful or infected? It sounds like I had the same thing with my yeast cappuccino though. Just hoping I can save it until the new year

 

[graysalchemy]

No it is that the yeast continue to produce some co2 plus the fact the green beer has co2 in it.

 

[rpt]

Alistair, am I right in thinking you didn't rinse the yeast before storing it? I've always rinsed it and so this would also get rid of any CO2.

 

[bbslaw]

Just an update. I used the remaining yeast in a young's harvest bitter the other day. Poured the green beer off the reserved jar, mixed the sludge up with some of the new wort and pitched it all in. It went off within a couple of hours and is bubbling away well a couple of days later. So there was definitely plenty of viable yeast in the unwashed cake. Will have to wait to see if there is any infection - not planning to open the FV until it's had 2 weeks, but all seems to be good so far!