Whats wrong with this idea?

[Hawks]

Interesting conversation....

my local micro top crops and re-pitches for each brew. He uses a strain from another brewery ( he guards which one it is ). He does this with each brew and has no lab facilities etc, if he gets a problem with his yeast he goes back to source for more. When I lost spoke to him about it he hadn't been back for at least a couple of years... Also in talking to him he did share that each brewery was different, he used to be a senior brewer at Gales ( before Fullers bought them and the brewery is now houses :twisted: ) having worked up from the labs. The yeast they used was very prone to mutation ( I think it may have been a multi-strain ).

 

[Hoppy]

Hi All

Callum, yes bottom cropping does happen, it is hard to top crop in a sealed FV. Sorry if I miss-read.

Yeast can only perform mitosis/budding around 26 times max, as the yeast cell wall is finite in its area (around 49-300micrometres for a 5-10micrometre cell) and because it has budding scars after mitosis, were it cannot bud from again.
You are correct, cropping early, we want these cells that have replicated less, less scars and have higher viability.

In reality, in the presence of oxygen (6-20ppm depending on strain or if air or pure O2 is used) you (commercially) only really yield 5-10 times the original volume of yeast, because once the oxygen is utilised (12-16 hours) it will almost fully cease to multiply and then ferment.

In home brew, where pitching rates are much lower, cell/ml and O2 levels with air reaches max 5-6ppm, it will replicate at the roughly the same number of times as a commercial brew (perhaps less even), but as the pitching rates were lower initially, more fermentation is expected from fewer cells (hence the longer fermentation), leading to cells that are larger, and therefore settle easily (in the presence of enough Calcium), ideal for home brew and smaller commercial brewers.

Dried yeast (and indeed starters made from these), when produced is propagated in the presence of very high levels of O2 and malt extract, plus extra nutrition, therefore is harder to propagate in breweries and home brew kits, for reasons mentioned above, this could be the reason you get 'drift' when using it in home brew as conditions are markedly different and the yeast cell are larger and older, therefore perform more sluggishly. They also want you to buy more yeast from them, as a one-hit. This also explains the reason your commercial brewer needs quite a high pitching rate and the trub nutrition for their fermentations. These yeasts also need very high levels of zinc for cell wall growth, much higher than in wet brewery yeasts. They also have a very low level of wild yeasts, that can propagate if yeast is re-used to a level where fermentation performance drifts, (stuck fermentations) and is non-flocculant.

Regards

Hoppy

 

[Titch]

i have to admit i didnt grasp all of what i have just read
but well done fellas
this type of conversation from basic grasps to real knowledge is what makes this a great place

think i need to read it again to understand all that is relevant to me

thanks again

G

 

[calumscott]

think i need to read it again to understand all that is relevant to me

I think all protagonists in the thread can agree on the most important bit:

For great beer, look after your yeasts as they were your own children.

Drown the buggers in sugary liquid...

*ahem*

I mean, show them love and care, feed them and nurture them, take care of them and protect them from the nasties out there in the big bad world...




...and get them to make your beer for you. :whistle:

 

[Hoppy]

Agreed Callum.

If we all did the same thing every time, we would all be drinking homogenised, bland & insipid dishwater (not that I have ever produced one of those ).

 

[brewtim]

Does creating a starter count as a generation in homebrew? If pitching up to around 4-10 generations is acceptable then each single starter and brew could potentially count as 2 generations, thereby reducing the number of brews that a single yeast could be used for?