Oxegenating wort

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Permalink Reply by Hillman on May 25, 2012 at 11:36pm

The Yeast book mentioned above says that you can aerate again after a few days. However I'm not sure if shaking the fermenter at the point would actually add any oxygen, as presumably the CO2 produced during fermentation has pushed the O2 out of the airlock. Shaking would definitely rouse the yeast, which would help with a stuck fermentation, but maybe not aerate the wort. 

How much aeration are you giving it before pitching? Maybe shaking it for longer at the start will solve the problem.

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Permalink Reply by Flanagan on May 26, 2012 at 11:48am

Point taken about the CO2, I think my aeration before pitching is pretty good.

Smiffy I think you may be onto the source of the problem as my mash efficiency is terrible - 55%. I do a BIAB on the stove and flick on and off the heat to keep it as close to 67C as I can. So despite checking the temps & stirring it around every 5 mins or so I can't assure myself I have it right on. I'm also thinking of asking for my grain to be milled twice and doing a slightly thinner mash than my usual 3L to 1kg ratio.

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Permalink Reply by Scarrfie on June 1, 2012 at 10:05pm

I put my bag in a chilli bin as with the mass of water it hold the temperature steady enough for an hour. Of course I went the next step and made my own bag from voile. I can get 80% efficiency using all the water in the mash at a 6:1 ratio. If I go 50/50 mash to sparge I can get 85 if I give it a really good stir with the sparge water.

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Permalink Reply by MrC on May 26, 2012 at 1:25pm

re. Irish Moss

Irish moss is a kettle fining agent and causes proteins to coagulate in during the boil.  Leaving the trub in the kettle help make the beer clear.  By the time fermentation is underway the Irish Moss's job is done.  Shaking the fermenter will re-cloud the beer but it will soon settle again.  

Irish Moss (or other kettle fining) added to the kettle will help remove protein haze.

Gelatine or Isinglass added to the fermenter will help clear the yeast.

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Permalink Reply by Hutch on May 27, 2012 at 1:24pm

You can also use olive oil to provide the oxygen to the yeast - read this thesis for more info: http://www.brewcrazy.com/hull-olive-oil-thesis.pdf

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Permalink Reply by Aidan Curran on May 27, 2012 at 11:01pm

Rock-a-by-baby is the way I do it - sit down on sturdy chair with fermenter horizontal across my knee, finger plugging the airlock hole and rock it back and forth. Turns it into froth in no time and minimum effort.

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Permalink Reply by martin w on June 2, 2012 at 5:26pm

i've been doing a bit of reading of the yeast book,here are some or the main points

yeast need oxygen to reproduce, low oxygen levels result in poor fermentaion performance and poor viability-more of a  problem if you repitch slurry.

lack of adequate oxygen can be resposible for stuck fermentations.long fermentation times,underattenuation,yeast stress and off flavours,it also lowers viability in yeast reuse

8-10 ppm is optimal for average worts but you should oxygenate based on yeast population- higher gravity=higher pitching rate=more 02 required

8ppm is the upper limit with air,trying to achieve higher rates with excessive times can be detrimental to head formation and retention

over oxygenation is rarely a problem unless is becomes very excessive,flavour problems can result such as increased fusel alcohols,increased acetaldehyde and others.

unless you are willing to buy measuring equipment the exact level of 02 is unimportant,should increase the level with each brew until you feel your beers are no longer improving and stick with that procedure

white labs did an experiment with 20 litres of 1077 wort-

shaking for 5 minutes    2.71ppm

pue 02 30 seconds       5.12 ppm

pure 02 60 seconds      9.2 ppm

pure 02 120 seconds    14.08 ppm

these worts were then pitched

the higher levels of 02 resulted in a faster by 2 days and more complete fermentation  by 1.004

also mentioned is a forced ferment test to do along side your brew which will normally finish between 1.001 and 1.002 lower than your beer,this will allow you to see if you have  a stuck fermentation.

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