Testing my Homebrew

[aj47]

I recently rediscovered my brewing kit and decided i'd have a go at making some good ol' home brew, however I forgot when it was meant to be bottled and it was left fermenting for about two weeks too long.

 

Hopeing for the best, me and a few friends drank a pint each today at lunch to find that I have created some kind of super brew which i'm still feeling te effects of four hours later.

 

I'm guessing it's roughly 7-8% but i'd really like to know exactly. Do any of you know of a way I can test my brew to see how alcoholic it really is?

[gcol]

I bet you are wishing you had used a brewing hydrometer at the appropriate stages.

 

If you remembered how much sugar you put in, and if your tastebuds tell you that all the sugar has been converted, A chemist (not me) should be able to tell you the conversion rate for sugar into alcohol. Sounds good. Drink it quick and make some more, just for the sake of science, of course!

[YT2095]

a Hydrometer is what I use, but you really should have known OSG before you started brewing it in order to get an exact calculation with the FSG.

 

the use of a Hydrometer now would only give you a Rough guide, and be in now way 100% as to the Alc%

[aj47]

hmm I didn't follow any recipe but off the top of my head it was roughly 1.5Kg for each demijohn, which is about 8 pints I think.

[YT2095]

well if you used proper Beer yeast, then it`s VERY unlikely that it`s going to be 7 or 8% after 2 weeks extra

I`ll tell ya that for nothin`!

 

and what were you doing brewing Beer in demijohns for crying out loud!????

[aj47]

What's OSG and FSG. I have little to no experience with brewing so I am very much at the amateur/experimental stage.

[aj47]

well if you used proper Beer yeast' date=' then it`s VERY unlikely that it`s going to be 7 or 8% after 2 weeks extra

I`ll tell ya that for nothin`!

 

and what were you doing brewing Beer in demijohns for crying out loud!????[/quote']

 

I was just judging by how drunk I got and demijohns were the suggestion of my aunt but I think she knows as little as I do on brewing.

[YT2095]

you`re looking at Barley Wine type strengths there, and beer yeast will die long before that stage.

it requires (surprisingly) a Wine yeast for that

 

also the use of a demijohn unless it`s a brown glass type is Not Good for beer at all!, in the dark and roughly 15c to 18c Max is all you need and tops 2 weeks before bottling it, and longer and you risk it tasting oxidised and "Mousey" (not at all nice).

 

did you rack the beer before drinking it?

[gcol]

What's OSG and FSG. I have little to no experience with brewing so I am very much at the amateur/experimental stage.

 

OSG is original specific gravity, FSG is final specific gravity.

 

Measure SG of brew just before adding yeast, which because of added sugar will be greater than 1 (pure water). When fully fermented, finished, the SG will be less. The reduction will show % alcohol. Brewing hydrometers are specially marked to change SG drop into % alcohol.

[YT2095]

oh yeah!, sorry about that, the OSG and FSG are exactly as Gcol pointed out, I didn`t see you post above your other post.

 

but in effect and for the future, if you take the OSG - the FSG and divide the difference by 7.36 (I think) that will give your % in alc.

 

double check this though as I tend to do stuff like this in my head without thinking when I look at a Hydrometer, but I`m fairly sure it 7.36

[gcol]

I still reckon that ideal conversion rate by yeast from sugar to ethyl alcohol must be calculable. Perhaps known by Woelen?

 

Think of it as a simple chemistry question and apply the result to the know initial quantities of water and sugar. Beyond me, though.....

[gcol]

Further thoughts on beer in demijohns: (corrections invited)

 

Beer requires a fast aerobic fermentation, which produces few volatiles and "off" flavours. Drink or bottle before the dreaded vinegar-fly gets it.

 

Fermenting in demijohns (closed fermentatiom) causes anaerobic fermentation, and more volatiles, suitable for very strong beers like barley wine (delicious) which are really wines made without grapes.

[aj47]

Aha thanks guys, great info.

 

I realised the main mishap from my previous brew is that I mixed and matched equipment from a wine fementing and beer brewing kit and didn't realise the importance of steralizing the equipment, which led to a few odd tasting pints.

Anyway this time i'm feeling slightly more motivated and i'm actually going to do some researh and attempt to create something that tastes half decent.

 

One thing though, from what i've read most home brewers use chemicals i.e sodium metabisulphite for steralising. Are these really neccessary or would a simple bleach solution be enough to kill any bacteria etc present?

 

Also I had an idea about calculating the alcohol content today. If I were to titrate a known amount of the alcohol with an oxiding agent such as acidified potassium dichromate or permangante, you could work out how much ethanol was oxidised to ethanoic acid and therefore the alcohol content. Although this would only work if the ethanol was the only thing being oxidised which I doubt it would be.

[YT2095]

you can use plain bleach, but try and buy the cheap stuff without the gells and scent and other agents in it, plain old Chlorox will work, as will hydrogen peroxide, it`s usualy a good idea to store you glass ware in a soln of these when not in use also, even the sterilising tablets for baby bottles is fine too, but don`t mix them with anything else.

with regards to the Sucrose, yeast won`t use that directly, it must 1`st break it down into glucose, which is why adding ordinary sugar takes longer to ferment out, it Does work, but you can add a few days to the process, and this might not be a good thing for a beer as that`s usualy done quickly.

a Crude way you could possibly work out the alc content would be to carefully distill a fixed quantity of it, say 100ml, and then work out the volume difference (taking the azeotrope into account).

it`s not Ideal, but will give a Rough indication.

the otherway would be to use a breathaliser and bubble air through the beer and take a reading from that, I`de like to see the results from such a test myself

but don`t blame me if it goes off the scale and breaks it!

 

 

edit: this now has a daughter thread if you`re interested: http://www.scienceforums.net/forums/showthread.php?t=19583