Accidental alcohol?

[Fizzycist]

TL : DR My ginger ale might be boozy?

After homebrewing for a few years, I decided on a whim to try making some (non-alcoholic) ginger ale. Without doing any sort of research, I boiled up some syrup, steeped some flavorings, cooled a bit but not much, added some salvaged yeast, and bottled, more or less following my normal sanitary procedures.
I bottled part of it in a 20 oz coke bottled. This was at about 10 am. I squeezed the bottle throughout the day. By 5 pm it was quite stiff with some bubbles around the surface. I popped the top and there was a nice fizz to it. So, I pasteurized the remaining glass bottles.
I proceeding to pour out the coke bottle and drink the contents. It tasted pretty good, not overly fizzy. However, towards the end I actually started to feel like I was getting drunk. WTF?
I had thought that with well aerated soda and a really short growing time the yeast would never get to anaerobic respiration and make some booze. What do you guys think?

 

[Yooper]

Oh, yes, when it carbonates it does produce some alcohol. However, it should be a minute amount, and safe for children- less than .25% and not enough to get drunk.

I suppose you could use a hydrometer and check it before and after, to make sure that it would be safe for children if that is a concern.

 

[Fizzycist]

Well, I mean I knew there could be a teeny amount, but I felt like I was drinking one of my 7% ABV brews! Was it all in my head?
And, not so much for children cuz it's quite spicy, but I've got some teetotaler friends I wanted to share with.

 

[aruzinsky]

I had thought that with well aerated soda and a really short growing time the yeast would never get to anaerobic respiration and make some booze. What do you guys think?

Where did you get the idea that oxygen matters in yeast fermentation? According to http://en.wikipedia.org/wiki/Ethanol_fermentation, alcohol is produced by the chemical reaction:

C6H12O6 + Zymase → 2 C2H5OH + 2 CO2

and there is no O2 here. The ratio of alcohol to carbon dioxide in the brew is fixed, provided that no carbon dioxide escapes the brew.

Molecular weights:

C2H5OH - 46
CO2 - 44

Mass ratio of alcohol to carbon dioxide = 46/44 = 1.05 .

According to According to http://www.manualslib.com/manual/383616/Eutech-Instruments-Carbon-Dioxide-Gas.html?page=13 ,
the maximum carbon dioxide concentration in carbonated beverages is 880 ppm or 0.00088. From this, the maximum concentration of alcohol in a brew, provided no carbon dioxide escapes, is

1.05* 0.00088 = 0.00092 = 0.092%

An obvious question is, "Does 880 ppm of carbon dioxide stop the fermentation process by killing the yeast?" I don't know the answer. But, incidentally, 12%-18% alcohol stops the fermentation process by killing the yeast.

Maybe, by "aerating" your soda, you allowed carbon dioxide to escape the bottle and that is why you had more than 0.092% alcohol.

 

[Fizzycist]

Well, if I remember from high school micro-bio yeast produces ethanol during anaerobic respiration. But, to paraphrase Dr. Hanson in Brew Chem 101, aerobic respiration consumes oxygen and sugar and produces a large amount of CO2 for each sugar consumed and produces no ethanol. He goes on to say that anaerobic, that is, after all the oxygen is consumed, respiration produces ethanol and much less CO2.

So thats why I figured so long as my soda started with a decent amount of oxygen, I could get decent carbonation before the yeast started to make any ethanol.

 

[Fizzycist]

And by aerated I just mean I splashed it around a bit before bottling. I didn't uncap it or something. There was no CO2 to escape.

 

[Yooper]

And by aerated I just mean I splashed it around a bit before bottling. I didn't uncap it or something. There was no CO2 to escape.

Yes, that's fine. You don't have to aerate the soda, but it won't hurt that you did. there is very little yeast reproduction needed to carb up a small batch of soda, so aerating vs not aerating is immaterial. But you don't get measurable c02 from yeast reproduction (the aerobic phase). Fermentation starts, and c02 is produced as a byproduct- carbing the soda.

 

[aruzinsky]

However, towards the end I actually started to feel like I was getting drunk. WTF?

The most likely explanation is that you were hallucinating. Maybe, your brew contained a psychoactive substance other than alcohol. Nutmeg comes to mind.

Before Lifeway Company changed ownership, I used to get a mild buzz from drinking Lifeway Cherry Kefir. I suspect that it had something to do with tryptophan.

 

[aruzinsky]

Where did you get the idea that oxygen matters in yeast fermentation? According to http://en.wikipedia.org/wiki/Ethanol_fermentation, alcohol is produced by the chemical reaction:

C6H12O6 + Zymase → 2 C2H5OH + 2 CO2

and there is no O2 here. The ratio of alcohol to carbon dioxide in the brew is fixed, provided that no carbon dioxide escapes the brew.

Molecular weights:

C2H5OH - 46
CO2 - 44

Mass ratio of alcohol to carbon dioxide = 46/44 = 1.05 .

According to According to http://www.manualslib.com/manual/383616/Eutech-Instruments-Carbon-Dioxide-Gas.html?page=13 ,
the maximum carbon dioxide concentration in carbonated beverages is 880 ppm or 0.00088. From this, the maximum concentration of alcohol in a brew, provided no carbon dioxide escapes, is

1.05* 0.00088 = 0.00092 = 0.092%

An obvious question is, "Does 880 ppm of carbon dioxide stop the fermentation process by killing the yeast?" I don't know the answer. But, incidentally, 12%-18% alcohol stops the fermentation process by killing the yeast.

Maybe, by "aerating" your soda, you allowed carbon dioxide to escape the bottle and that is why you had more than 0.092% alcohol.

CORRECTION:

I misread my reference. "880 ppm" is not the maximum carbon dioxide concentration. From http://chemistry.stackexchange.com/...arbon-dioxide-content-of-a-soda-can-or-bottle , the maximum concentration is approximately 10,000 ppm.

1.05* 0.010000 = 0.0105 = 1.05%

So, I suppose it is possible to be buzzed.