Odin wrote:I like the testing that's going on. But - for myself - there are a few things I'd like to take into consideration before pitching so much yeast:
1. The amount of foam up would mean you can only use a small part of your fermenting vessel;
4. Stirring won't help, since it will add new oxygen and affect total reachable ABV;
You can have a stirring paddle inside the fermenter. Or a pump. Beer guys use them. Both will remove the foam to a non problem. As will a pressurized system. I have seen some talk about pressure systems being able to reduce toxins.
Odin wrote:
2. Bigger ferments create more heat, yet have less side cooling, so the faster the ferment, the hotter it will get when you increase total ferment batch size;
3. Above 37C the yeast will start to die, giving off flavours;
Yeah good point. It's relatively cold where I am so this is not as big a problem, heating is. But for a lot of people it would be.
Odin wrote:5. Product versus sediment ratio is low;
Why? The yeast will reproduce to hit the same density , if not more, if they can. 50g dried yeast per litre is not the speed limit. I got linear increases in production from 5 to 10 to 20g per 400ml. If 20g was near the limit it wouldn't have been so linear. What I mean by that is reproduction will likely occur to hit or exceed the same cell density in the solution regardless of start pitch. Only if the starting pitch of yeast contains enough live cells to overwhelm the desired cell density is it overpitching. All other amounts, including the huge amounts I use is not overpitching, it's actually under pitching. The yeast will hit the same density regardless, provided it can (ie enough nutrients), all I'm doing is giving that "base of yeast" a much higher starting count.
Until I hit the point where adding more yeast does nothing to speed you can be sure I am currently underpitching. It seems bizarre especially due to beer/wine guys who can say even small amounts is overpitching, but they are under a different set of rules. They need lag time, they need reproduction, so without it you are under/over pitching to hit a beer/wine ferment of a particular type.
Odin wrote:
6. Add that to the already low fill rate of the fermenter and the short potential fermenting time in a bigger batch (yeast death above 37c) and you even less total output;
7. I wouldn't call your product cleared, by looking at the pictures, Hooch;
8. More yeast & faster ferments means ... more yeast and more CO2 so clearing will be a bitch;
9. Meaning any time advantages you may have found ... will translate in having to distill twice at least to get rid of yeast taste in the low wines;
10. Esterification takes place more in longer ferments, so this procedure (or parts of it) may only work when one wants to reach a more neutral drink. Then again ... see point 9.
I am working on a system to clear a finished ferment within 2 hours. If you had to wait 48 hours to settle a 10 hour 10% wash I would agree, it's ridiculous, who would care about fermenting so quick in such a situation?
My belief is getting the wash separated from the yeast as soon as you can will reduce the toxins, as will lowering reproduction rate. It's not even personally proven to myself yet as I haven't done all the testing I want, but it's where I'm headed to see if it is the case.
Odin wrote:
What I find interesting is the low pH drop. And I am curious to how that comes. Any sugar wash I did immediately crashes to pH 3.0 when fermentation reaches + 30c temperatures.
My experience with rum ferments is that I have to struggle (or temp control fement with double boiler) to keep temp below 35c. That's on a 50 gallon ferment with 0.5 to 0,75 grams of yeast per liter of fermentation. And the amounts of BiCarb I have to use to keep pH above 3.5 are impressive but not to my liking. Think 1 to 1.5 grams per liter of fermentation.
I'm only interested in sugar washes and neutrals so you have to take where I'm going with that in mind. Brown spirits need flavor, ie yeast reproduction, lag times, long settling, etc, to get the flavor they have, just like wines and beers. My experience on that front only relates to beers, wines and cidars, I have little interest in rums, whiskeys, etc so haven't learnt much about that process.
As to low ph drop, once the dried yeast is placed in the wash it starts to "reenergize" itself which lowers the PH. I have done about 5 tests on this for the first 30 minutes of the fermentation. It's pretty interesting. At my reverse osmosis/sugar/yeast start PH of about 6.1 the yeast drop the PH to 4.6.If you start PH higher they don't drop it as low, if you start lower it goes lower, the acidity should be a fixed amount based on number of yeast "rehydrating". However I have seen some contrary evidence to this in my tests, but nothing I can replicate yet. I have a suspicion yeast have some way of prematurely stopping their "building up" for conditions if the acidity hits optimal range. For highest speed fermentation of glucose obviously being in ~4.5ph to 5.0ph is where you want to be due to the enzymes involved operating best in that range.
Some excerpts from Chris White's yeast book.
Upon inoculation into wort, the cells first utilize their glycogen reserves and any available oxygen to revitalize their cell membranes for optimal permeability and transfer of nutrients and sugars. The cells rapidly absorb oxygen and then begin to pick up sugar and nutrients from the wort.
When you pitch yeast into wort, it begins acclimating to the environment. Although you do not see any activity, the cells begin the uptake of oxygen, minerals, and amino acids (nitrogen) from the wort and build proteins from the amino acids. If the yeast cannot get the amino acids they need from the wort, they produce them.
This is why the PH lowers, and it lowers very quick in my tests that have low lag time. My lag time is usually 10 mins at 30C and by 10 mins the ph 6.1 drops to 4.6 and that is when the foaming begins. It takes another 30-45mins to drop the PH again, which I think is caused by carbon dioxide. RO water doesn't have a PH "buffer", but the dried yeast I use does increase PH slightly. Probably not enough to care about, but I always measure with the yeast in and dissolved to be more accurate with it. Usually increases it by .1 or .2 depending upon amount. I thought my 15.35% ABV test would have a PH in the 3.5 to 3.8 range at end but it was 4.1 . This was surprising to me given the length of time compared to others, but it is what it is. PH 4.1 is still in a relatively good range for production.
If you use tap water.... its variable quality could be a reason why you are experiencing low PH issues. Not sure, but I do know with just distilled/RO water, sugar, yeast and/or epsom salts, in the range of 2% to 15.35% ABV the PH is never lower than 3.8 in my testing by end of fermentation. If yours is with same ingredients maybe your dried yeast is different than mine or the water is different. Can't see what else could be causing it unless the fact it's a larger batch is somehow making it more acidic? More toxins produced due to higher temps like you mentioned? Many things to look into for that problem.
I know some dried yeasts have acids in them to "help" with fermentation, turbo yeasts have a bunch of rubbish too.