dropping system

[MARMITE]

when using the dropping system for secondary fermentation, do you deliberately re-aerate the wort or do you syphon it as quietly as possible to avoid introducing air ?

[Jim]

At that stage you should try to keep air out of your beer - otherwise you risk oxidation. In fact as soon as the initial vigourous fermentation is finished air is undesirable in your brew.

[Graham]

when using the dropping system for secondary fermentation, do you deliberately re-aerate the wort or do you syphon it as quietly as possible to avoid introducing air ?

Haa! You've hit my Achilles heel.

Depends upon when you drop and what you regard as dropping. If you drop early, it is best to aerate, by early I mean around 36 hours after pitching or before the gravity has reached about half of the expected attenuation. If you are dropping late, or your dropping is just into something like demijohns as per Dave Line's teachings, then aeration is best avoided.

It depends upon the yeast strain, but usually, it is best to aerate when dropping, otherwise fermentation can stop dead or slow considerably. However, you do need sufficient active yeast when dropping to use up the oxygen, but if fermentation has proceeded too far, the yeast will not be active enough to scavenge the air, and this can be dangerous.

There are some people that swear by dropping and have had no problems with it, myself included, but others have experienced fermentation simply stopping dead. The problematic drops in my view are do with too little yeast being carried across and too little air in solution to encourage more growth.

However, don't aerate if fermentation is close to finishing.

[Jim]

Yeah, I was thinking more of the practice of racking off into closed containers under airlock. Apparently that's quite popular with some homebrewers.

[Graham]

Yeah, I was thinking more of the practice of racking off into closed containers under airlock. Apparently that's quite popular with some homebrewers.

Yes, as per the teachings of Ken Shales and then Dave Line. Probably a hangover from the early teachings of winemakers turned brewers. Some people keep their beer under airlock for weeks in demijohns, like in winemaking. I'm not sure that I approve, but I've never done it, so I don't really have a say. Lots of people are okay with it though.

[oblivious]

Yeah, I was thinking more of the practice of racking off into closed containers under airlock. Apparently that's quite popular with some homebrewers.

and it keep out the creepy crawlies

[oblivious]

I reckon the problems occur with modern bottom fermenting, flocculant ale yeasts. I'm tempted to drop next time I use get some Ringwood yeast but I don't think once would be enough and i'd still need to aerate.

I would have though during active fermentation there would be yeast through out the wort?

[Graham]

I reckon the problems occur with modern bottom fermenting, flocculant ale yeasts. I'm tempted to drop next time I use get some Ringwood yeast but I don't think once would be enough and i'd still need to aerate.

Yes, there are several pitfalls.

A major one is that our fermenters are much shallower than the ideal, commercial ones, which by convention is six feet. It means that the majority of the yeast is either sitting on the top, or the bottom and not in suspension. The yeast is carried up in the wort when it produces a bubble of carbon dioxide, and falls back down again when it releases it. This critical distance is six feet. By the time it has risen five or six feet it releases the bubble and sinks, and by the time it has sunk five or six feet it has generated another bubble and starts to rise again. This keeps a lot of yeast in suspension, whereas in our case, with only about 18 inches of depth, it doesn't get this opportunity, and consequently a lot of our yeast is sitting on the bottom, waiting to produce another bubble. So it is a possibility that an inadequate amount of yeast is carried across.

Another point is sterol and fatty acid synthesis. Yeast needs sterols and fatty acids for effective operation and it usually builds lipid and sterol reserves during the aerobic phase of its life cycle. Some yeasts are better at synthesising sterols than others; northern yeasts (Ringwood) are not capable of building enough reserves to see it through fermentation so needs to be aerated frequently to encourage synthesis of the necessary bits and bobs. However, in poorly aerated worts the yeast can utilise fatty acids in the trub, and not bother to synthesise everything it needs. Rack it off this trub and its source is taken away, and fermentation stops.

Then there is yeast type. I too am not sure if these bottom yeasts, that are allegedly in our packages, are suitable. They may sit on the bottom come what may and never really get into suspension in any great amount.

I have always had access to commercial yeast. Originally it was yeast taken from a Guinness bottle, but even so, when we had a local home brew shop come real-ale off-licence, they supplied real live Morland's yeast (who did drop) straight from the brewery.

I will say that although I have never had a problem with dropping, I have had more letters on this particular subject than any other. I think that I was probably OTT on my recommendation of keeping air out of contact with beer after initial aeration. It caused a certain amount of paranoia, to the point that some worts are probably under aerated.

I would suggest Daab, that if you are going to drop with Ringwood yeast, you'll certainly need to aerate. Ringwood type yeasts need frequent aeration even when they don't drop - that's what the fishtails are for.

[MARMITE]

Just got back from the pub and amazed I have stimulated so much interest. The story so far is as follows:

I am trying to brew an authentic pedigree but substituting flaked maize for maltose syrup as Daab suggested because the later is unavailable. The brew was designed at 80% mash efficiency but as I had 2 different pedigree yeast cultures from 2 different pubs I increased the ingredients by 50% and also achieved 94% mash efficiency. The upshot was I ended up at 9 1/4 gallons of wort at 1045. I pitched 5 1/2 gallons with saffale 04, 3 gallons with 1 pedi culture and the other 3/4 gallons with the second pedi sample. The wort was very well aerated.

Wort 1 with saffale 4 was a little sluggish and had only 1/2" head at most. After 48hrs gravity had dropped to 1030. I transferred this to demis after
re-aerating and has been going well for the last 24 hrs.(foaming out of the demi without an air lock).

Wort 2 (Pedi Yeast) After 72 hrs still with minimal cover, still at 1030, transferred into demis, well aerated and seems to be picking up.

Wort 3 (Pedi yeast) After 72 hrs down to 1022, well aerated and seems to be picking up.

I obtained a further sample of Pedi yeast. A small mash using a thermos flask, dropped the gravity from 1045 to 1015 in 72 hrs.

Re-aeration seems to be doing the trick but I am concerned about the risks.

[Maltloaf]

I always drop the beer, even though I only use dry yeasts. This is mainly so that I can pick and choose when to bottle - I'm not always able to run my life to the yeast's schedule!

This applies, in my experience, to S23, T58 & MPG.

I syphon the beer from primary into an airlocked fermenter once the yeast head has begun to recede, anytime between 24 & 48 hours from pitching*. At this point there is still plenty of yeast in suspension and it gets on with clearing the headspace of air immediately - the airlock starts bubbling straight away.
It does leave a lot of trub behind, the sediment that is left when I bottle (i.e. what was carried over in the syphon + whatever the yeast has done in the meantime) is a lot cleaner than that in the primary. I can then either pitch the yeast straight into some fresh wort or bottle it and use it later.

I appreciate that this goes against some of the advice given on this (and other) forums, but it works for me.

*If you're late dropping then the yeast will be quite sluggish, but I've never had it have a problem finishing the job off.

Cheers,
ML.

[MARMITE]

[quote]If you are using S04, don't bother with dropping and in both cases don't use demis[/quote]

Thanks for the replies. The reason I dropped the SO4 at 30 was because the yeast cake was very thin and almost exposing the surface of the beer. Isn't this better than risking oxidisation - or am I missing something?

Also why do you advise against using demis Daab and what else would you use to maintain sterility? (Perhaps another 5gallon vessel with a fermentation lock?)