abv lower than stated on kits

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sloth

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Following my musings on the St Peters ruby red review thread, why do so many, myself included fail to achieve the stated abv on a kit? I generally seem to have plenty of action for up to 5 days, then the gravity just won't change. Even after a gentle stir and another week or two.
Temps are always in the 18-21ºC range.
I've read some say dry pitching the yeast kills some off, but surely if the sugar is there to feed on, what yeast there is will multiply.

*In my mind the kits have x amount of sugar, which will produce x amount of alcohol. Surely if made up to the given volume with water the abv should be pretty damn close. Unless for some reason the yeast can't feed on all the sugar, but then if the yeast has stopped doing its thing how does the brew undergo secondary fermentation?

Thoughts, experiences and opinions please...
 
sloth said:
Following my musings on the St Peters ruby red review thread, why do so many, myself included fail to achieve the stated abv on a kit? I generally seem to have plenty of action for up to 5 days, then the gravity just won't change. Even after a gentle stir and another week or two.
Temps are always in the 18-21ºC range.
I've read some say dry pitching the yeast kills some off, but surely if the sugar is there to feed on, what yeast there is will multiply.

*In my mind the kits have x amount of sugar, which will produce x amount of alcohol. Surely if made up to the given volume with water the abv should be pretty damn close. Unless for some reason the yeast can't feed on all the sugar, but then if the yeast has stopped doing its thing how does the brew undergo secondary fermentation?

Thoughts, experiences and opinions please...
Click to expand...

How much yeast is in the kit?

Lots of kits only give you 5g-7g to save money. For a 23L brew you need 10g-11g ( depending on OG)
 
If this is the case why do they not just put a*little*extra in - it cannot be much more cost. And wouldn't the yeast, whether 7g or 11g multiply until the food source (sugar) is used up anyway?
 
sloth said:
If this is the case why do they not just put a*little*extra in - it cannot be much more cost. And wouldn't the yeast, whether 7g or 11g multiply until the food source (sugar) is used up anyway?
Click to expand...

I imagine that extra 4g-7g multiplied over thousands of of kits getting churned out comes to quite a chunk of change.

I'm not knowledgeable enough in the biology of yeast to give you a definative answer but I guess the yeast can only multiply a finite amount, no matter how much sugars are there before it starts to produce alcohol. Otherwise it would replicate infinately till it took over the world :lol:
 
MyQul said:
I imagine that extra 4g-7g multiplied over thousands of of kits getting churned out comes to quite a chunk of change.

I'm not knowledgeable enough in the biology of yeast to give you a definative answer but I guess the yeast can only multiply a finite amount, no matter how much sugars are there before it starts to produce alcohol. Otherwise it would replicate infinately till it took over the world :lol:
Click to expand...

Having thought about it and had a quick read of the relevant section in GW's book, one thing that restricts yeast growth is oxygen, that's why you need to aerate your wort to get the yeast growing. Once the oxygen in the wort has been depleted the yeast starts to produce alcohol in an anaerobic environment
 
Hmm, interesting. ...
I was not aware yeast needed anaerobic conditions to produce alcohol - I thought it was a simple byproduct of 'eating' the sugars.
Next question: aerating the wort is easy enough by pouring the water from a height into the fv, but should the yeast be simply sprinkled on top where (presumably) the most oxygen is, or stirred into the mix?
 
sloth said:
Hmm, interesting. ...
I was not aware yeast needed anaerobic conditions to produce alcohol - I thought it was a simple byproduct of 'eating' the sugars.
Next question: aerating the wort is easy enough by pouring the water from a height into the fv, but should the yeast be simply sprinkled on top where (presumably) the most oxygen is, or stirred into the mix?
Click to expand...

Wasn't something I was aware of till I got recently got GW's book for my birthday. Seems the sugars are used to reproduce rather than create alcohol.

Doesn't matter about sprinkling or mixing, i've found (although some people advocate one or tother), the (dry) yeast will drop to the bottom of the FV. The yeast will eventually finds it's way to the sugars in the wort wherever it is
 
It is extremely hard to over pitch and very easy to under pitch. I would recommend making a starter at least 4 hours if not the night before. Also, yeast needs to go through a aerobic fermentation to multiply, after all of the oxygen is used, up it will then start the anaerobic fermentation. If you can, oxygenate your wort with pure O2 for 10-20 seconds with a carbonation stone. Cheers and happy brewing!
 
hpg972591 said:
It is extremely hard to over pitch and very easy to under pitch. I would recommend making a starter at least 4 hours if not the night before. Also, yeast needs to go through a aerobic fermentation to multiply, after all of the oxygen is used, up it will then start the anaerobic fermentation. If you can, oxygenate your wort with pure O2 for 10-20 seconds with a carbonation stone. Cheers and happy brewing!
Click to expand...
And how do you propose to oxygenate your wort with O2 ?
 
First and foremost I hope you understand O2 is the short hand version for oxygen. Secondly, if you look at my previous post I said to use a carbonation stone. If you're not sure where to get one check with your local homebrew shop. As for the oxygen you can get a tank at a welding supply store.
 
I really don't follow a lot of this - I pitch in the little pack of yeast and whatever the FG of the brew there's something like half an inch layer of yeast on the bottom of the FV. So multiplication of yeast hardly seems to be a problem. I always get a really good krausen, usually within hours of pitching as well, but occasionally the FG is a bit on the high side. I can only assume the malt has a bigger percentage of unfermentable sugars, but hey, what do I know: I just chuck stuff in a bucket and a few weeks later I drink it. :lol:
 
Cwrw666 said:
I really don't follow a lot of this - I pitch in the little pack of yeast and whatever the FG of the brew there's something like half an inch layer of yeast on the bottom of the FV. So multiplication of yeast hardly seems to be a problem. I always get a really good krausen, usually within hours of pitching as well, but occasionally the FG is a bit on the high side. I can only assume the malt has a bigger percentage of unfermentable sugars, but hey, what do I know: I just chuck stuff in a bucket and a few weeks later I drink it. :lol:
Click to expand...

I regularly get a lower FG than expected. Its all to do with yeast attenuation. I always use nottingham yeast ((Wilko's ale yeast) cuz it's cheap which is a high attenuating yeast

"Attenuation percentage is the percentage of sugars that yeast consume. Attenuation varies between different strains. The fermentation conditions and gravity of a particular beer will cause the attenuation to vary, hence each strain of brewers yeast has a characteristic attenuation range. The range for brewers yeast is typically between 65-85%."

http://www.whitelabs.com/beer/homebrew/beginners-attenuation-and-flocculation-definitions
 
MyQul said:
"Attenuation percentage is the percentage of sugars that yeast consume. Attenuation varies between different strains. The fermentation conditions and gravity of a particular beer will cause the attenuation to vary, hence each strain of brewers yeast has a characteristic attenuation range. The range for brewers yeast is typically between 65-85%."

http://www.whitelabs.com/beer/homebrew/beginners-attenuation-and-flocculation-definitions
Click to expand...

Ah, so presumably brewers who know what they're doing choose a yeast that will stop fermenting at the desired point for the sweetness of the ale they want to produce? I'm afraid I only do kit beers, and they're not exactly forthcoming with what yeast they provide, hence my previous post, but presumably this would be quite important to AG homebrewers.
 
MyQul: "I regularly get a lower FG than expected. Its all to do with yeast attenuation. I always use nottingham yeast ((Wilko's ale yeast) cuz it's cheap which is a high attenuating yeast"
So a lower FG depends not on the amount of yeast pitched but on the strain? Just adding extra won't make a difference?
And if one were to augment the kit yeast (perhaps to be sure it coped with extra fermentables for a higher ABV) would it need to be the same strain as the kit sachet? Or could one add any decent ale yeast an the two strains would work happily together?

Cwrw666, Have you ever had an issue with a supplied kit yeast?
 
Cwrw666 said:
Ah, so presumably brewers who know what they're doing choose a yeast that will stop fermenting at the desired point for the sweetness of the ale they want to produce? I'm afraid I only do kit beers, and they're not exactly forthcoming with what yeast they provide, hence my previous post, but presumably this would be quite important to AG homebrewers.
Click to expand...

Your right. With AG you can choose a liquid yeast (I believe there are even things such as yeast catalogues) that is appropriate to the style of beer your brewing eg if you were to brew a dry stout, an appropriate yeast would be a irish ale yeast or if you were to brew a bitter an english ale yeast would be appropriate. But you don't have to follow the most appropriate yeast. You can just use a generic dry ale yeast like I do, as liquid yeasts cost about £6, which I cant afford. But if your going for authenticity an appropriate liquid yeast is the way to go.

Having said all that about cost, it's possible to harvest the yeast from commercial bottles of beer that have been bottle conditioned and not pasteurized
 
BruinTuns said:
MyQul: "I regularly get a lower FG than expected. Its all to do with yeast attenuation. I always use nottingham yeast ((Wilko's ale yeast) cuz it's cheap which is a high attenuating yeast"
1. So a lower FG depends not on the amount of yeast pitched but on the strain? Just adding extra won't make a difference?


2. And if one were to augment the kit yeast (perhaps to be sure it coped with extra fermentables for a higher ABV) would it need to be the same strain as the kit sachet? Or could one add any decent ale yeast an the two strains would work happily together?

Cwrw666, Have you ever had an issue with a supplied kit yeast?
Click to expand...


1. As per the quote, getting a lower attenuation depend on factors like fermentation conditions and gravity and the strain of yeast you use so I don't think simply adding more will get you a lower FG. I always try to pitch the correct amount of yeast using a yeast calculator but always seem you get a lower FG because I use Wilko's Gervin Ale (Nottingham) yeast which is has a low attenuation, not because my fermentation conditions are perfect (Far from it as I don't have a brew fridge)

2. Don't know the answer to this but my gut instinct would be not to mix different strains of yeast one brew. If your planning adding extra fermentables and need extra yeast I would get a 11g pack from somewhere and use that and keep the kit provided yeast for another brew
 
MyQul said:
Your right. With AG you can choose a liquid yeast (I believe there are even things such as yeast catalogues) that is appropriate to the style of beer your brewing eg if you were to brew a dry stout, an appropriate yeast would be a irish ale yeast or if you were to brew a bitter an english ale yeast would be appropriate. But you don't have to follow the most appropriate yeast. You can just use a generic dry ale yeast like I do, as liquid yeasts cost about £6, which I cant afford. But if your going for authenticity an appropriate liquid yeast is the way to go.

Having said all that about cost, it's possible to harvest the yeast from commercial bottles of beer that have been bottle conditioned and not pasteurized
Click to expand...

And presumably although you've spent that much on yeast you can save money by saving some yeast from the bottom of your FV if your hygiene is good. In the past, to speed up the brewing process I've done this. I found 2 brews from a sachet of yeast to be fine, but a third one was a bit dodgy. But there again my sanitation process is at best a bit sloppy :lol:
 

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