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Can acidic environment kill beneficial bacteria?

Answered on August 19, 2014
Created December 12, 2011 at 8:32 AM

I know that heating does, but what I would like to know is if adding lemon juice to my kefir/yogurt will cause similar effect?
Protein becomes denatured by both heating and adding some acid to it and that made me wonder.

7b11ed525ffa23bc7257684e27488a6a

(366)

on December 13, 2011
at 02:09 PM

Too bad Helicobacter pylori aren't killed off by gastric acid.

32f5749fa6cf7adbeb0b0b031ba82b46

(41747)

on December 12, 2011
at 03:59 PM

True enough that it's not acidic denaturation of proteins that cause microbe death, but gastric acid does kill quite a few bugs.

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3 Answers

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4
7b11ed525ffa23bc7257684e27488a6a

(366)

on December 12, 2011
at 01:14 PM

Lactobacilli produce lactic acid as a result of fermentation. It is the acid (and added salt) that keeps pathogenic molds from forming on the fermenting products. IOW, they like an acidic environment. Only some strains can survive the stomach acid to reside in the colon, though. Here is a bit more on that.

http://www.ncbi.nlm.nih.gov/pubmed/3106442

I don't think adding lemon, vinegar or any other such substance will make any difference. It's the stronger gastric acid that will be the bigger issue.

2
Cf32992bfa1907147c7cdc451bba9c63

on December 12, 2011
at 03:05 PM

There's this organ called the stomach. It too is acidic.

And acidic denaturing of protein != killing of microorganisms.

32f5749fa6cf7adbeb0b0b031ba82b46

(41747)

on December 12, 2011
at 03:59 PM

True enough that it's not acidic denaturation of proteins that cause microbe death, but gastric acid does kill quite a few bugs.

7b11ed525ffa23bc7257684e27488a6a

(366)

on December 13, 2011
at 02:09 PM

Too bad Helicobacter pylori aren't killed off by gastric acid.

1
96bf58d8c6bd492dc5b8ae46203fe247

(37227)

on December 13, 2011
at 01:34 AM

I make both water kefir and yogurt at home.

My understanding is that many of the probiotic microbes do make it through the stomach. In many cases, you don't have a stomach full of food at the time you ingest them so they pretty much go straight through without lengthy exposure to stomach acid. I eat my yogurt in the morning before I've eaten a meal and I drink the water kefir in mid-afternoon a while after I eat.

I've also read that the microbes in the yogurt are beneficial but don't necessarily colonize your gut while the water kefir may actually lead to some colonization by good microbes which then crowd out bad types.

The latter must be true, because when I started drinking it (in small daily doses) I could definitely feel something going on although I was fortunate not to have any "die-off flu." And after the transition, I found I could tolerate yogurt for the first time in my life although the richer, high-fat stuff I make at home has caused me to scale back my daily amount from what I had eaten of the commercial "live culture" stuff.

EDIT: With regard to your question about lemon, I brew the water kefir twice--once with the "grains" which are microbe colonies, and once after straining out the grains (but of course leaving a ga-zillion free-floating microbes.) During the first brew, I put in a chunk of lemon but don't squeeze it. This encourages rather than impedes the fermentation. For the second round, I squeeze the lemon chunk and add fruit juice then seal it so carbonation builds while the bugs eat the sugars in the brew. Since it becomes ever less sweet and more bubbly, I consider that proof that the lemon has no negative effect.

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