Yeast Starters

[adams81]

I liked it and appreciate the scientific approach. Too many things in brewing seem to be tradition that has evolved into 'fact'. It's nice see these questioned. Keep up the good work G rock!

[AllanMar]

I don't know what the point of this experiment was, oxygenated beer tastes bad.... I thought that was a well known fact.

Do you want to know what the "point" was or are you just wanting to put my efforts down.

The "point" was to find out how much the beer would become oxidised on the stir plate in 24 hours. I was hoping it wouldn't be enough to be of concern, and that I would be happy to pitch 3L at high krausen. It was a check before I did that, and I was disappointed to find that it was very oxidized. It was an experiment to help me decide whether to pitch a stir plate starter at high krausen, or chill and decant.

If it seems a stupid thing, and is of no use to anyone, let me know and I'll delete the post.

The point of the stir plate is to oxidize the wort, so that's a good thing.

This is a discussion forum and you don't have to delete it based on what anyone (especially me) says, you should be prepared for people to disagree/criticize in a discussion though.

[GuingesRock]

The point of the stir plate is to oxidize the wort, so that's a good thing.

The point or a stir plate is to oxygenate and not oxidize wort. There must be a compromise somewhere between providing enough oxygen for the yeast to grow at a good rate, and oxidizing the hell out of the starter wort/beer.

[Ladd]

I think you have the right idea there Mark and you are accomplishing exactly what you set out to do: take a finished beer and oxidize it to see what it tastes like (SHIT! ). The difference is, you're not thinking of pitching oxidized beer into your wort, you're thinking of pitching a fermenting starter which is going to have a totally different composition than that of your oxidized beer.

I am sure you know this but to reiterate, the point of the stir plate is to enhance the growth phase by continuously mixing oxygen into the wort for the yeast to use during growth rather than actually fermenting the wort, granted fermentation is also taking place to some extent. Again the composition of the starter is totally different than that of a finished beer and at high krausen there will not be any oxygen left in the wort.

Also needing to be considered is the fact that the oxygen that is being put into the finished beer in your experiment is reacting with the different compounds (oxidizing them) of the finished beer; components which will not yet be present in the starter. Oxygen being put into the starter is being consumed by the yeast during growth and normal aerobic respiration.

I think a more appropriate experimental design to test your parameters would be if you made a 3L starter, pitch your yeast, put it on the stir plate and taste it at high krausen/when you would be ready to pitch it. This will give you the most accurate idea of the flavor profile of the exact thing you are thinking of pitching into your wort.

One other thing to note is that yeast on a stir plate may not show signs of fermentation or it may happen so quickly once the yeast population is established that you may not notice.

Loving your enthusiasm and ideas, keep it coming!

Edits for spelling and grammar mistakes

[GuingesRock]

Thanks very much. That all makes sense. So there’s hope yet for pitching my whole 3L starter at high krausen.

After your post, I think what I’ll try next, is with my first starter, I’ll grow it on the stir plate for 36 hours and then chill overnight. The next day I’ll decant the liquid off the top of the yeast and taste it. If it isn’t too bad, then I’ll be good to go next time without chilling and decanting.

I expect everyone who uses a stir plate has tasted that decanted liquid and knows the answer …just, I don’t.

Thanks for the help.

ps. The experiment was useful for learning what oxidized beer tastes like. It's something I won't forget that easily now.

[Ladd]

Thanks very much. That all makes sense. So there’s hope yet for pitching my whole 3L starter at high krausen.

After your post, I think what I’ll try next, is with my first starter, I’ll grow it on the stir plate for 36 hours and then chill overnight. The next day I’ll decant the liquid off the top of the yeast and taste it. If it isn’t too bad, then I’ll be good to go next time without chilling and decanting.

I expect everyone who uses a stir plate has tasted that decanted liquid and knows the answer …just, I don’t.

Thanks for the help.

ps. The experiment was useful for learning what oxidized beer tastes like. It's something I won't forget that easily now.

Sounds like a solid plan! Keep us posted!

[GuingesRock]

Thanks, will do. Thanks also Geoff for the encouragement.

Being the persistent bugger that I am ...I have some more beer on the stir plate spinning at a slower rate with just a dimple on the surface. There has to be a way of oxygenating adequately without oxidizing too much.

Here's a great article on oxidation of beer: http://www.homebrewersassociation.org/z ... -gone-bad/" onclick="window.open(this.href);return false;

[RubberToe]

Mark, I think the key to not over oxidizing a starter my be to stop the stir plate once the yeast are done. Even so, It might not matter - not because of the "dilution theory", which I don't buy.

The question is, do the yeast clean up this oxidation?
Do yeast that are finished the growth phase, and finished fermentation, clean up oxidation?
Is beer oxidation a reversible process or is it permanently chemically altered?

Even if the finished yeast in the starter don't clean up the oxidation, once they're pitched into the fresh wort they very well may.

Has anyone consulted the yeast book on this? I doubt this is a topic overlooked by generations of scientists.

[mr x]

The stirring should be shut off once the starter is done. I slow mine down as it looks to be finishing. That's advice from wyeast.

Sent from my Nexus 4 using Tapatalk 4

[adams81]

This is why I decant - it simplifies things. There's no need to plan a starter so that it is at high krausen on brew day and there is very little concern about adding unwanted flavours. Although my lag times may be a little longer than others as long as my sanitation is up to snuff I don't see any drawback. Thoughts?

[GuingesRock]

This is why I decant - it simplifies things. There's no need to plan a starter so that it is at high krausen on brew day and there is very little concern about adding unwanted flavours. Although my lag times may be a little longer than others as long as my sanitation is up to snuff I don't see any drawback. Thoughts?

My thoughts, for what it's worth, is you are right about everything you said there so succinctly. I put some beer on the stir plate at low speed with just a dimple and it tasted just as bad. I still have to make my first starter on a stir plate, chill, and taste the decanted liquid as a final test.

Some flavour compounds can spoil your beer at incredible dilutions, (one pancake in a stack of pancakes high enough to reach the moon sort of territory). For example amyl mercaptin (produced by yeast) has a flavour threshold of 0.00000007 mg/l (Principals of Brewing Science page 35), and that's enough to fail your beer at a comp. I'm not saying the stir plate produces more amyl mercaptin, it may do, I don't know.

I'm doing some more reading trying to find out the answer to Rob's question about whether yeast can clean up products of oxidation. I don't think they can, but I don't know.

My impression so far is if you use a stir plate, you should chill the starter and discard the liquid. From what people have said though on this thread ...If you don't use a stir plate, that may not be necessary, as it's "just a small batch of plain beer." I think the way to test that would be to chill and decant a small portion of the starter and taste the decanted liquid. Amartin already did that, and I'm quite happy to take his word on that.

More or less. I used to decant off, and then drink it, because why not?

The instructions that arrived with my stir plate say emphatically that there is no need to chill and decant. I don't think they are right. The manufacturer should get on with importing stir plates from China, and not tell people how to brew.

[GuingesRock]

Mark, I think the key to not over oxidizing a starter my be to stop the stir plate once the yeast are done. Even so, It might not matter - not because of the "dilution theory", which I don't buy.

The question is, do the yeast clean up this oxidation?
Do yeast that are finished the growth phase, and finished fermentation, clean up oxidation?
Is beer oxidation a reversible process or is it permanently chemically altered?

Even if the finished yeast in the starter don't clean up the oxidation, once they're pitched into the fresh wort they very well may.

Has anyone consulted the yeast book on this? I doubt this is a topic overlooked by generations of scientists.

Rob, I just read an incredible, detailed chapter, on oxidation, in the Principals of Brewing Science (I'm loving that book). Iso-alpha acids from hops are powerful antioxidants and will help to prevent staling (oxidation), but there is no mention of them being able to reverse oxidation. No mention of yeast cleaning up oxidative products. Also discussed with my biochemist wife, and she thought it was unlikely.

Also of interest: One of the major offenders, trans-2-nonenal, which produces the papery/cardboard off-flavours, has a flavour threshold of 0.0001 mg/L

[RubberToe]

Good find. I still haven't gotten around to looking for this in the Yeast book.

[NASH]

Rob, I just read an incredible, detailed chapter, on oxidation, in the Principals of Brewing Science (I'm loving that book).

I thought that book was too rich for your blood??







Transmitted from the Hop-phone.

[GuingesRock]

Rob, I just read an incredible, detailed chapter, on oxidation, in the Principals of Brewing Science (I'm loving that book).

I thought that book was too rich for your blood??







Transmitted from the Hop-phone.

No, it's what Guinges likes. I always liked chemistry (knew the periodic table by heart at 16) I keep reading it over and over. Those isocohumulones however are too rich for my blood. Seems I've been brewing to minimize them without knowing it. What's his big book like? is it worth $250, or does the little book have the crux of it all?

[NASH]

Ohh, that's what happened to you!

I was thinking about the other book! It's not big though, just expensive

It's good, I like it though an entirely different sort of book, more on the practical side of things

[GuingesRock]

Ohh, that's what happened to you!

I was thinking about the other book! It's not big though, just expensive

It's good, I like it though an entirely different sort of book, more on the practical side of things

Thanks Nash. Can't stop. Have to get back to my book again.

[GuingesRock]

Well, Who would have thought it! I had my starter on the stir plate going for 48 hours, then chilled and just decanted and tasted the decanted liquid and …….

It tastes awesome! I drank a wine glass full and I feel like having another. It’s full of peachy flavours from the yeast (conan). I’d have no worries about pitching this starter whole. Yet the beer that I put on the stir plate for just 24 hours tasted really foul (see above).

I wonder what went on there. Any thoughts? I think I had the whirlpool going at proper speed (about ½” dimple on the surface). I think the yeast prevented oxidization. Maybe the absence of hops had something to do with it.

I’m interested to know if anyone else has tasted their decanted liquid from stir plate starter and if it tastes good, or badly oxidized.

[Tony L]

[ If a seagull flew over and shat in my soup, I wouldn’t stir it in and carry on eating, no matter how many thousand times it was diluted. .

I guess you won't be eating Bird's nest soup very soon then

I haven't made a starter in years using all dry yeast like I do, but when I did make them I decanted the spent liquid especially as I did 1 gallon starters for lagers.
I really should shake the cob webs off my stir plate and do a liquid yeast to compare results between dry and liquid strains of American Ale yeast.

[GuingesRock]

FG of chilled and decanted starter liquid from the conan starter that spent 48 hrs on stir plate is 1.006. It really is beautiful stuff. I want that in my beer, and I'm probably going to be a high krausen dump it all in person. Pale as anything and no dark colour from oxidation. Not a hint of flavour of oxidation either, just peach and alcohol with a hint of yeast.

[GuingesRock]

I think the wort in the erlenmeyer on the stir plate is initially oxidated. As the yeast starts to use up the oxygen it produces carbon dioxide. The CO2 which is heavier than air, is held in the erlenmeyer with its narrow neck and foil cover, and blankets the surface of the starter, protecting the surface of the starter from exposure to air and further oxygenation of the wort. The yeast then uses up the rest of the dissolved O2 and no oxidation occurs. This may only apply to a starter that has been on the stir plate for less than 48 hours as eventually the CO2 would stop being produced and would diffuse out of the flask to be replaced/diluted with oxygen carrying air.

[RubberToe]

Bingo, my thoughts as well.

Sent from the brew timer.

[adams81]

Mmmm, fresh starter.

I like to drink it and see what flavours the yeast are contributing, especially since my starters are all the same recipe!

[GuingesRock]

Mmmm, fresh starter.

I like to drink it and see what flavours the yeast are contributing, especially since my starters are all the same recipe!

That's smart.

Do you use a stir plate? Does it never taste oxidized?

My wife brought six different stir bars home from work just for me to try them and see what kind would work as the ones I bought didn't work. Three of them are useless, don't start or get thrown right away and three work great even at max speed, including one really huge one and one small one and one med size (5l water in erlenmeyer).

[Celiacbrew]

I'm a newbie to brewing, so take this with a grain of salt, but it seems to me there might be something different between the yeast starter and the beer in your keg that you worry about becoming oxidized. Alcohol would be the big one but I suspect that there are probably a few other chemicals too. If some of them are involved in the oxidation reactions then that might explain why people can use 2l starters without getting off tastes.

This article mentions alcohol as being an important piece of oxidation in beer.
http://beersensoryscience.wordpress.com ... eer-aging/" onclick="window.open(this.href);return false;