Spent Yeast experiment

[Oaty]

We all know the routine. Clean & sterlize the carboys. Add the wash, nutrients and pitch the yeast. In a particularly lazy frame of mind an idea struck me. I'm adding dead yeast - in the form of nutrients- to my wash. Why not try just using the old spent yeast instead. Concept. Instead of cleaning & sterlizing each time let's try just pouring the wash directly over the spent yeast save a couple steps and save the old yeast as nutrients. I realize that you can't continue this ad infinitum, but the concept is interesting.

Experiment: 2 normal sugar washes with all nutrients added
2 sugar washes with spent yeast plus nutrients added
2 sugar washes with spent yeast with only minimal nutrients DAP, Epson, 1/2 normal B vitamin complex

Comparison of Abv

Concerns: Bacterial problems from old batch


At this point I'm probably using way too much B complex & nutrients. So, in order for the experiment to have validity I need to decide on a minimum viable base line of B-complex & nutrients. What do ya'll use and how much? Don't respond with tablespoons of nutrients as that is useless. I would need to be able to quantify this in constitiuent parts.- DAP, Epson, dead yeast, vitamins- B, B complex , Folic Acid , C etc.

I've already started the 6 batches, but they will not really have any validity this time around as I need the forementioned minimum baseline control/

So, what do you use?

[CoopsOz]

I only make UJSM these days, it's easy and produces good results with minimum effort. I do as you describe, I never wash or sterilise my fermenter. Once a finished wash is racked in to my boiler, i put fresh water over the old lees, this is so they don't die. I then do my run, once finished I tap some hot backset into a bucket and dissolve my sugar. Once it has cooled I then pour straight back in the fermenter.....there is no yeast/nutrients or anything else added. If the ferment starts to slow down I skip the use of backset for a couple of runs.

[HookLine]

Don't respond with tablespoons of nutrients as that is useless.

Is that a request or an order?

[Oaty]

Hardly an order It's just that 'Yeast Nutirent' is a bag of something...yeast, hulls, vitamins, citric acid it's a collage of nutrients. I just wanted specific ingredients such as DAP, B-complex, Folic Acid, Epsons, etc. That way it might be compared.

[Oaty]

After re-reading your post I should say that I was refering to a sugar wash so the nutrients are a necessary evil. When brewing I did the same as you.

[wineo]

I sometimes reuse yeast on sugar washes with no problems.If you use enough yeast,and keep the gravity below 1080SG,the only thing you really need is some acid{citric} to lower the PH,and some DAP.The dead yeast provides most of the other neutrents.You have to use alot of yeast for it to work,and make sure to kill some of it.The more stuff you add to a sugar wash,the more it will make flavors so I take a less is more approch.

[Oaty]

Well, I'm new to this and just followed the home site. I've been using DAP, Epson, Acid , Vit B complex, Folic Acid Vit C and for a little overkill a bit of Yeast nutrient. However, you have the experience. I'd be glad to cut all the extraneous out. It's complicated & it's not cheap. My experience is in Brewing where none of this is necessary. So, I was just following directions.

[wineo]

I still use DAP,epsom salts,gypsum,and citric acid in my sugar washes.I dont add the vitimans,and use alot more yeast in there place which makes a cleaner product because the vitimans add a little flavors.I have been monkeying around with these washes trying to get less flavors using a potstill.Im always still learning also.

[muckanic]

Experiment: 2 normal sugar washes with all nutrients added
2 sugar washes with spent yeast plus nutrients added
2 sugar washes with spent yeast with only minimal nutrients DAP, Epson, 1/2 normal B vitamin complex

Comparison of Abv

Concerns: Bacterial problems from old batch

With this experiment, you're manipulating yeast pitching rates as much as nutrients. More active yeast pitched means less initial aerobic growth, which generally means less cogeners like esters and fusel oil. So ABV may not be the only criterion for comparison; you could also look at proportion of heads/tails, and neutrality of the hearts. Are you planning to treat a stripping run with alkali? (coz that would reduce some of these differences). Amount of yeast that makes it into the boiler should also be a consideration, ie, how soon is the run after the ferment? I somehow doubt whether common nutrients are actually volatile enough to make it into the distillate, but they can certainly impact yeast metabolism and the formation of byproducts.

Personally, I would be more concerned about build-up of wild and mutated yeast than of bacteria, particularly if the ferment is closed. Spontaneous acetic ferments are actually quite rare; sub-threshold lactic ferments are a bit more common.

[Oaty]

I'm using a reflux so the taste is really not a factor. I could throw in anything & it's not likely to make it past the condenser. I've even managed to get rid of the 'Tasty Turbos'. Yeast pitching rates would not be a factor. Although that my be an interesting variable in future, I am effectively killing all used yeast by pouring the hot wash over them and adding cold water to cool & adjust brix by volume. The old yeast are just another nutrient. I just thought it might be interesting to find out what the nutrient effectiveness of the old yeast might be.

I've started the trial by using the parameters listed above. However, it would be more valid if I used a minimal value standard of nutrients. That is the smallest value of nutrients able to get the job done. From there I could see the true effect the old yeast had.

As it is my standard witches brew is probably overkill on nutrients and thus the nutrient value of the yeast could well be negligible. A base line needs to be established. What do you use ? And how much? I probably need to run several runs of the established minimum base line. Confirm that it works then try varying amounts of nutrients in the old yeast to have any validity.

Also, the old yeast is in the sludge of the old batch there might be carry over from old batches. There has to be a standard for the base line as it's sludge is the testing medium.

[rumbaba]

I have my greatest results by syphoning the finished wort off fruit washes ala tater and just adding water and sugar to the lees. Goes off like a cracker and gives a great product. Made over 50 bottles of plum brandy and well on the way to exceeding that with pear brandy with this method. Still havn't moved on to the 3 bushells of peaches frozen down in Jan. Next I think I will try Coops method and disolve the sugar with hot backset from a run. Always striving to improve I think the point of the addition of citric acid is an important one, I always add a tsp and thus far have had no complaints.

[Oaty]

It seems a consensus on this subject is going to be impossible to obtain. I went back to the home site and re-read several stickies on the subject, read several threads in the forum. MNbody seems to agree.I seem to be getting answers from a little dap all the way to all of the above. The basic list is Dap,Epson,Citric Acid, Vitamins...

Some use only dap and acid others even go so far as to use a full spectrum vitamin. Some say 3 vitamins others none. For the test to be valid a minimum has to set. If I am overdosing then any effect could be left over nutrients in the sludge or could show no effect at all due to the fact that all needs are be met already from the over-abundance of nutrients.

So far the above batches are showing results. I'm not sure as to the meaning as I am using a yeast strain that I've no personal experience with. The control had the usual dosing of all the above. It took off slow very slow in my experience must be the yeast. Control 2 spent yeast & nutrients took of slowly but was bubbling happily within 24 hours. Experiment spent yeast only dap, acid & 1/2 B complex took of almost upon contact. Not sure if this means anything as I haven't really established the control. But at least the yeast seems to like the spent yeast.

[nutmg1]

Oat,
The best example of a simple sugar wash that I've seen along the guidelines of less is best is Birdwatchers Sugar Wash. Bakers Yeast, Lemon Juice and Sugar, Tomato Paste. That's it.

I'm no expert but I've made several gallons of this wash and its very clean. Almost seems to easy when your making it.

[muckanic]

If I am overdosing then any effect could be left over nutrients in the sludge or could show no effect at all due to the fact that all needs are be met already from the over-abundance of nutrients.

I'll repeat it, ABV might not be the best criterion. Yeast are versatile critters, and can find alternative biochemical pathways in order to grow, making different byproducts in the process. Your column won't necessarily separate all byproducts from the EtOH. Lack of nutrition is the obvious concern with the baselining, but excess nutrition could also have an effect in principle. I am thinking particularly of all the lipids contained in the spent yeast cake, and what their eventual biochemical fate might be.

[partonken]

i use spent yeast all the time in my 23 litre sugar washes. i add a small tsp of distillers yeast just for safety, and they take off every time! I also use 100% backset for my SW which means there is alot of dead yeast in the backset when i start a new batch.

When you re-use backset all the time you have to raise the ph , using potassium bi-carbonate or another alternative.

After about 4 or 5 batches you start to accumulate too much yeast and you have to throw it out or split it in too and start 2 batches of SW> Cheers!

[muckanic]

When you re-use backset all the time you have to raise the ph , using potassium bi-carbonate or another alternative.

So exactly how acidic does your backset get? A crisp white wine must has a pH of 3.5, and yeast seem to ferment that OK.

[partonken]

my sugar washes get as low as 3.6 and i add 4 tbsp of potassium bi-carbonate which brings it up to 4.6.

You have brought up a good point! how low would the backset go if i didnt adjust the ph?

And how low does the ph have to go before the yeast give up the ghost?

you say your must gets to 3.5 ph , i think the lowest my backset has ever got was 3.4

i will have to do an experiment and see how low i get after a few runs and see how the yeast react. let you know when i get my results.

[wineo]

I think at 3.0 or lower,things come to a crawl,or stop completely depending on the yeast strain.Ive ran some white wine ferments at 3.5-3.7 Ph but usually run the rest of my wines at 4.5.If you go too low on wine,it will give you heartburn.Im not so picky on sugar washes,as long as its 5 or under,its good to go.

[muckanic]

A FOAF (OK, it was me!) once attempted to ferment Coca Cola @ pH 2.0 for reasons which are now obscure. No go there.

[belialNZ]

A FOAF (OK, it was me!) once attempted to ferment Coca Cola @ pH 2.0 for reasons which are now obscure. No go there.

I did that once, as an experiment. Some friends drink a lot of Coke and were really fussy about it being flat, so I asked them to keep all the half bottles they usually wash down the sink.

I went for the simple idea of diluting it to reduce pH, added a lot of yeast, and waited.

It fermented exceedingly slowly, but it fermented. The 12 litre batch only distilled to 1 litre (at 50%), and there was a very large amount of dead yeast sludge.

It had a recognisable coke taste, very chemically, and when mixed with coke, tasted... as you would expect... like coke.

Other than an initial tasting I never drank the stuff, but took it to a party to show a bunch of friends and they finished it off happily.

Not an experiment I plan to repeat.