Slightly continuous fermentation

[PeteB]

My fermenter holds more than twice the volume of wort produced from one mashing. (RYE)

Recently I mashed then pitched yeast. The next day I did another mash and added the wort to the fermenter that had now been going for 24 hours.

I added no extra yeast because I assumed the original yeast had multiplied and there would be enough for the next lot of wort.

All appeared to work well. Yield was satisfactory and spirit flavor was similar to past fermentations.

Are there any negatives to this technique?

[JohnD]

None at all. If your mashing technique is good, the yeast will build some biomass at first and begin fermentation. Then when you push the second mash into it you'll get a bit more biomass produced and right back to fermentation. The only drawback I can think of is it might slow down your total fermentation time a bit. It's a great way to maximize the use of your equipment capacity.

[ViolentBlue]

My fermenter holds more than twice the volume of wort produced from one mashing. (RYE)

Recently I mashed then pitched yeast. The next day I did another mash and added the wort to the fermenter that had now been going for 24 hours.

I added no extra yeast because I assumed the original yeast had multiplied and there would be enough for the next lot of wort.

All appeared to work well. Yield was satisfactory and spirit flavor was similar to past fermentations.

Are there any negatives to this technique?

You can keep your yeast going like that for a number of generations. you may find that eventually it will peter out and you'll need to repitch.

not sure about the reason for the yeast slowing down, but it can happen.

[Beauport Bob]

I think some that know more than I would recommend doing the two mash ins then add the yeast. But,

I imagine if you are top loading (splashing) into the fermentation tank you may happily introduce some additional oxygen. Keep an eye on the temperature and ph difference between the two.

[WI Distiller]

I know many breweries (including my former employers) who used a similar technique, even getting triple sized fermenters and adding a third batch of wort. If your fermentation takes off quickly and finishes in the amount of time you are looking for, there is no down side at all.

[Denver Distiller]

This is a common technique used in German brewhouses in particular. There it is called Drauflassen, and for the most part, you want to "top up" the fermenter when the 1st wort you put in the fermenter is at, or approaching, high krausen. IMHO, you would need to be sure to aerate the incoming wort.

So long as you are consistent with your approach, this could give a nice note characteristic of your distillery. Most yeast strains I've worked with tend to produce more esters when using this technique. It's a good way to make Kolsch, IMHO, because you get nice esters and a drier attenuation.

[PeteB]

Thanks for the positive comments. The first time I did this it was by necessity. I had started the next mash and discovered I had run out of dry yeast. I had spare room in the active fermenter so I tossed the wort in there instead of wasting it, and hoped for the best.

The wort is pumped in at quite a reasonable pressure so I am getting a fair amount of aeration.

I doubt it would be a good idea to wait until I have 2 mashes in the fermenter before adding yeast because the first one may get an infection while waiting, I can't cool it. Also I would need twice the amount of yeast.

I read somewhere on this forum (i think) that fermentation should be allowed to progress without interruption or it could produce off-flavours, hence part of the reason for starting this thread.

Denver D, what do you menan by "approaching, high krausen" and how do I know when that is?

[Denver Distiller]

It simply means when your fermentation is at its most aggressive. An easy visual cue is when the rye foam is at its highest point on the side of your fermenter.

[PeteB]

Thanks D.D, I will try to adjust my mashing to deliver wort at "high krausen" although I can only adjust timing be a whole day or a few hours. I am over working in distillery through the night. Could use a holding tank but that means more equipment and more chance of infection.

[Denver Distiller]

Well, if you're mashing the next day, you should be ok. So long as that yeast is close to high krausen, you should be ok. Generally, you just want to be sure that it's as active as possible, and that it's not starting to go into lag phase again.

There are some potential drawbacks to this method, like potentially oxidizing positive congeners formed in that 1st batch, but give it a go, and see if you're happy with the result. You also want to think about not shocking that yeast with colder temps with the second batch.

Cheers

[Brian]

There is a fair amount of research out there on Simultaneous Saccarification and Fermentation (SSF) as an energy saving method during on of the last oil crisis....worth a look.

[PeteB]

Thanks Brian, I will have a search for it, but in the meantime, do you think the technique could be used in my situation where I lauter?