pH Safe-Zone to Kill Enteric Bacteria

[TAK]

After a spontaneous inoculation, how low should the pH be to ensure that any enteric bacteria has died off?

Similarly, how much calculated ABV to achieve the end?

Of course, the drop in pH goes along side the drop in gravity. I will be testing both and want to know what results should make me fell safe tasting it.

 

[ColoHox]

The Enterobacter only contributes character for the first few days of fermentation. Once the Saccharomyces gets going, the drop in pH (below ~4.4) and the presence of ethanol deactivate/kill it.

Calculating the exact ABV from a mixed fermentation is tricky. Turns out, using the change in gravity is a decent estimate. The drop in pH doesn't always correspond with a drop in specific gravity.

 

[TAK]

Thanks for the input. I remember reading that post from TMF a while ago. I'll take a gravity sample, if it's dropped, and the pH is around <4.4, and it doesn't smell foul, I'll give it a sip.

 

[dantheman13]

Thanks for the input. I remember reading that post from TMF a while ago. I'll take a gravity sample, if it's dropped, and the pH is around <4.4, and it doesn't smell foul, I'll give it a sip.

From what I understand, Botulism is the highest threat of death. If the wort does not lower it's pH to < 4.5 within 5 days, there is an extremely small chance that Botulism spores can produce their toxin (http://beerandwinejournal.com/botulism/)

I've read that 7-8% of poisoning from E. coli O157:H7 cases cause death. I know that E. coli lives in lambic for a couple of days before pH and alcohol kill it off (http://suigenerisbrewing.blogspot.com/2014/02/fact-or-fiction-can-pathogens-survive.html). I don't know how long it takes for E. coli to produce it's toxin (Shiga-toxin), and whether the toxin can survive fermentation if it was produced beforehand, therefore I don't know what the fermentation time frame is where you should worry about Shiga-toxin being in the wort.

The other food poisoning viruses/bacterias/molds give you vomiting or diarrhea, but can't kill you:
http://www.foodsafety.gov/poisoning/causes/bacteriaviruses/
http://www.fsis.usda.gov/wps/portal...d-handling/molds-on-food-are-they-dangerous_/

 

[TAK]

Thanks for the links.

Although I suspect that my spontaneous inoculation went well and is safe, now I'm leaning towards 'but is it worth it?' In my case, I took about 3/4 gallon of extra wort, boiled it separately and left it out to inoculate. Maybe I'll try another spontaneous inoculation, but less whimsically, and in a more prepared way. I think for ease of mind, it's worth it to reduce the pH of the wort before setting it out for inoculation.

 

[Oldsock]

From what I understand, Botulism is the highest threat of death. If the wort does not lower it's pH to < 4.5 within 5 days, there is an extremely small chance that Botulism spores can produce their toxin (http://beerandwinejournal.com/botulism/)

The bacteria that causes botulism really only thrives in an anaerobic environment (usually created by the canning process). As far as I am aware the risk of creating botulism toxin during a standard spontaneous fermentation is essentially zero.

Like botulism (where it is the toxin not the bacteria itself causes issues) other entric bacteria can produce biogenic amines that some people have an allergic reaction to. This will persist after the pH is lowered below 4.4. If you want to be extra safe, you can add acid to achieve that lower pH pre-fermentation. It would only account for about 10% of the acidity of the final beer (assuming a final pH of 3.4).

 

[dantheman13]

The bacteria that causes botulism really only thrives in an anaerobic environment (usually created by the canning process). As far as I am aware the risk of creating botulism toxin during a standard spontaneous fermentation is essentially zero.

That's a good point. Thanks for pointing that out to me.

 

[TAK]

Hmmm? I boiled the wort in a 4 qt pot, and then I took the boil pot outside, covered with cheesecloth, to cool. 12 hours later I pored it through a funnel into a 1 gal carboy, no additional aeration.

After boiling, the wort would be a pretty anaerobic medium. Since I didn't provide any agitation for 12 hours, could that be enough if an anaerobic environment to pose a risk?

 

[dantheman13]

Hmmm? I boiled the wort in a 4 qt pot, and then I took the boil pot outside, covered with cheesecloth, to cool. 12 hours later I pored it through a funnel into a 1 gal carboy, no additional aeration.

After boiling, the wort would be a pretty anaerobic medium. Since I didn't provide any agitation for 12 hours, could that be enough if an anaerobic environment to pose a risk?

Chris Colby indicates here that it is a possibility, but I am not sure how much he considered the aerobic/anaerobic nature of boiled wort during open air inoculation: http://beerandwinejournal.com/q-a-botulism/

 

[ColoHox]

Hmmm? I boiled the wort in a 4 qt pot, and then I took the boil pot outside, covered with cheesecloth, to cool. 12 hours later I pored it through a funnel into a 1 gal carboy, no additional aeration.

After boiling, the wort would be a pretty anaerobic medium. Since I didn't provide any agitation for 12 hours, could that be enough if an anaerobic environment to pose a risk?

Your wort was not anaerobic, especially after pouring through a strainer. As oldsock mentioned, canning is a problem because of the sealed environment. Anaerobic means the bacterium can ONLY grow when oxygen is absent. Also, Clostridium does not grow below pH 4.5, and the growing, toxin producing cells are what one would worry about.

 

[TAK]

Your wort was not anaerobic, especially after pouring through a strainer. As oldsock mentioned, canning is a problem because of the sealed environment. Anaerobic means the bacterium can ONLY grow when oxygen is absent. Also, Clostridium does not grow below pH 4.5, and the growing, toxin producing cells are what one would worry about.

What I was saying is that after boiling my wort, I let it cool outside in the same pot. I didn't pour it through a strainer; it sat undisturbed in the boil pot for 12 hours before transfer to the carboy. It's always been my understanding that boiling degasses wort (which is why we always add O2 back). Also, I did not adjust my wort pH down to <4.5.

 

[ColoHox]

What I was saying is that after boiling my wort, I let it cool outside in the same pot. I didn't pour it through a strainer; it sat undisturbed in the boil pot for 12 hours before transfer to the carboy. It's always been my understanding that boiling degasses wort (which is why we always add O2 back). Also, I did not adjust my wort pH down to <4.5.

Right. By strainer I meant funnel. Yes, your wort was degassed. However, you did not remove the oxygen in the headspace and seal the container. Your wort was not anaerobic.

People have been making mixed culture lambics for a thousand years. Wort itself, in most cases, and the finished beer, do not provide appropriate growth conditions for Clostridium, especially when combined with a mixed culture of other bacteria which can grow in the wort and use the available nutrients.

 

[TAK]

Thanks for all the feedback. There was some good info here. I keep in going back tho the position: I'm sure it's fine, but given how easy it would be to replicate again with the added measure of adjusting my wort pH, is it really worth the risk. I think I'll probably err on the side of abundant caution and dump this batch. Maybe in the spring I'll give it another shot.