Yeast starters and use of glucose

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DocAnna

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There's something rather satisfying about a yeast starter, the flask quietly whirring away in the corner of my home office turning from a dark brown, to foamy cloudy amber then lastly light gold with settled yeast. This one is the Omega OYL-107 for another batch of the red festbier which I'm vacillating between discouraging upset and determination to improve, after the LAB feedback. Anyway, this was a comment about yeast starters I thought would be helpful to share, as I'd wondered whether I could economise by using a blend of dextrose and malt extract, or even increase the OG with dextrose to improve the yeast cell count yield.

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So I've read these two papers which really helped
How Glucose additions to yeast with maltose rapidly suppresses the genes to allow maltose digestion, within half an hour. It's not clear though how quickly the ability to digest maltose can recover though.

This shows how even small additions of glucose to starter wort depresses yeast growth and attenuation. Though annoyingly the data charts shown aren't complete and don't fully explain the text narrative.

All of which is consistent with John Palmers' statement in How to Brew that
"Yeast that has been eating a lot of sucrose, glucose, and fructose will quit making the enzyme that allows it to eat maltose—the main sugar of brewer’s wort."

Long way of saying don't add glucose to your starter, and it's really making me think that using brewing sugar to increase gravity is not a great idea either - not that I've done so for a long time but it is a thought.

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Brew_DD2

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I think if you're planning on harvesting the yeast from a batch, then you've made a good point. It's likely not a good idea if you've used a good dose of simple sugars (such as in a Tripel or Golden Strong).
 

DocAnna

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I think if you're planning on harvesting the yeast from a batch, then you've made a good point. It's likely not a good idea if you've used a good dose of simple sugars (such as in a Tripel or Golden Strong).
That's a really good point! I was thinking that if you do want to add dextrose to increase ABV then it should be added at secondary once the maltose has been consumed as otherwise attenuation will be reduced and fermentation take longer.
 

Brew_DD2

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That's a really good point! I was thinking that if you do want to add dextrose to increase ABV then it should be added at secondary once the maltose has been consumed as otherwise attenuation will be reduced and fermentation take longer.

I suppose it depends to what extent glucose suppresses the genes that allow for maltose digestion. Anecdotally, I can't say I've ever noted any issues with fermentation lag or reduced attenuation with sugar additions. Quite the opposite tbh. Though that could be due to sufficient cell count and health at the time of pitching.

I definitely keep sugar away from my starters though, for all the reasons you've stated.
 
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That's a really good point! I was thinking that if you do want to add dextrose to increase ABV then it should be added at secondary once the maltose has been consumed as otherwise attenuation will be reduced and fermentation take longer.

Doesn't have to be in secondary, it can be as primary approaches FG, although the yeast will probably want a rouse as (to simplify) the flocculation mechanism gets turned on by low sugar levels. But it's no bad thing to not add sugar before the start of fermentation, although it's convenient to get it to dissolve in boiling wort, at high gravities (which is when it's normally used) it is putting more osmotic stress on the yeast.

But in the real world, the convenience and reliable dissolution of adding it in the boil tends to outweigh other factors unless you're doing stupid-big beers.
 
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I'm vacillating between discouraging upset and determination to improve, after the LAB feedback.
Pay no heed to the what the LAB people said: it’s ruddy great! Beer is for enjoyable drinking not ticking boxes against some arbitrary style guidelines :-)
 

JockyBrewer

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Pay no heed to the what the LAB people said: it’s ruddy great! Beer is for enjoyable drinking not ticking boxes against some arbitrary style guidelines :-)

As one of the 'LAB people' - I do agree! A one off style competition judging doesn't mean your beer is bad, so please don't be discouraged.

For one thing, if you're confident in the beer and want to win a competition then enter it into another competition and see whether you get similar feedback.

But beyond that, just enjoy your beer.
 

St00

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I've had great results just repitching slurry with my recent lager ventures. I dump the initial trub after a week and when fermentation has finished I just rinse the remaining trub with cooled boiled water and pop it in a big flask. Pour off the excess liquid after 24 hours in a fridge and I'm good to go for the next batch.

Obviously there's a minor risk involved, but lagers are so easy to make (at least the brewday) and a lot of issues arise through sup par yeast health/pitch rates, that this seems to tick all the boxes. I've been brewing near enough 1 a week using this method.
 

Clarence

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So I've read these two papers which really helped
How Glucose additions to yeast with maltose rapidly suppresses the genes to allow maltose digestion, within half an hour. It's not clear though how quickly the ability to digest maltose can recover though.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC215083/pdf/jbacter00239-0311.pdf
This shows how even small additions of glucose to starter wort depresses yeast growth and attenuation. Though annoyingly the data charts shown aren't complete and don't fully explain the text narrative.
http://braukaiser.com/blog/blog/2013/07/07/yeast-growth-on-malt-and-sugar/
You say that, and I've always believed it and I never make a starter with glucose. But. Isn't glucose present in the wort anyway, together with maltose and maltotriose, in varying proportions? And what about when I add a significant amount of table or candi sugar to a strong Belgian, or invert sugar to a heritage recipe? There's going to be a significant amount of monosaccharides in the wort before the yeast even hits it and yet the yeast doesn't seem to stall when there are only maltose and/or sucrose left to ferment.
 
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You say that, and I've always believed it and I never make a starter with glucose. But. Isn't glucose present in the wort anyway, together with maltose and maltotriose, in varying proportions? And what about when I add a significant amount of table or candi sugar to a strong Belgian, or invert sugar to a heritage recipe? There's going to be a significant amount of monosaccharides in the wort before the yeast even hits it and yet the yeast doesn't seem to stall when there are only maltose and/or sucrose left to ferment.

All these things are shades of grey, but there's only 7-10% glucose in typical wort, if the yeast wants to get anywhere, it needs to get its maltose-munching enzymes going.

And yes, anecdotally, Belgian beers do seem to be the ones that stall most often for homebrewers, although some yeast like WLP530 are far worse than others.
 

DocAnna

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You say that, and I've always believed it and I never make a starter with glucose. But. Isn't glucose present in the wort anyway, together with maltose and maltotriose, in varying proportions? And what about when I add a significant amount of table or candi sugar to a strong Belgian, or invert sugar to a heritage recipe? There's going to be a significant amount of monosaccharides in the wort before the yeast even hits it and yet the yeast doesn't seem to stall when there are only maltose and/or sucrose left to ferment.
The braukaiser article suggests that small amounts of glucose does depress attenuation and slows utilisation of maltose, so it is possible that adding simple sugars in these beers is a contribution to overall sweetness and residual sugars. I do though think you have a point in that most yeast would be expected to be able to recover maltose utilisation over time, but over what time and to what detriment in terms of yeast stress and esters is not clear.
 

Clarence

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The braukaiser article suggests that small amounts of glucose does depress attenuation and slows utilisation of maltose, so it is possible that adding simple sugars in these beers is a contribution to overall sweetness and residual sugars. I do though think you have a point in that most yeast would be expected to be able to recover maltose utilisation over time, but over what time and to what detriment in terms of yeast stress and esters is not clear.
Maybe there are other variables at play. I know that my Whitbread Pale uses 10% invert sugar in wort of OG 1045 and is down to 1008 around 48 hours using S-04. What I haven't tried, though, is using successive generations of yeast harvested from this brew in subsequent batches of the same beer (and I'm not going to either). Even the Ancients knew about this and Dave Line warns against making yeast starters with glucose as it would change the character of the yeast "over a few generations, causing the cells to elongate"!
NB, above mentions anecdotal evidence that home brewers often experience difficulty getting some Belgian beers to attenuate properly and I wonder if this isn't more a character of the yeast than the composition of the wort. I understand yeasts like Dupont Saison are known to stall whatever the composition of the wort.
Working with another forum member, who makes a Belgian Trippel with nearly 20% added sucrose, I observe that this ferments out like a dream, dropping from 1080 to around 1006 in a couple of weeks. He does use successive generations off the same yeast in the same recipe. I suppose the wort temperature and acidity isn't sufficient to hydrolise much of the sucrose in the last 10 minutes of the boil, so that doesn't really count as evidence. Interesting topic, though, and I don't think we've got quite to the bottom of it yet.
 
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