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How do bacteria in sauerkraut stay alive?

  1. Feb 15, 2017 #1
    When I make sauerkraut after adding salt I pound the cabbage with a wooden mallet to release its juice. Then I press it hard into the jar. I was wondering how the lactobacillus that ferment the cabbage survive the pounding and pressing. Thanks.
  2. jcsd
  3. Feb 16, 2017 #2

    Andy Resnick

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    Bacteria will barely 'feel' the mechanical forces- maybe a tickle :) What is more disruptive is the pH, but even so, bacteria are fairly hardy. Remember, all your gut bacteria had to first survive a trip through your pH 0 stomach and then time in your duodenum- an environment that completely destroys fats, proteins, and carbohydrates.
  4. Feb 16, 2017 #3
    As a layman I wonder why. If I slam my fist down hard on a counter, the bacteria between my fist and the counter most likely is still there right? Why does it not get smashed? :)
  5. Feb 16, 2017 #4

    Andy Resnick

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    Bacteria (and plant cells) have a rigid cell wall- granted, there are many different flavors of bacterial cell walls, but let's keep it simple for now. The bacterial cell wall can support a pressure difference of about 20 atm (http://www.textbookofbacteriology.net/structure_5.html), which translates to about 300 pounds /in^2. So, if you want to mechanically crush a bacterium, you will need to apply about 40 atm positive pressure (since the inside of the bacterium is osmotically pressurized with respect to the outside), or 600 lb/in^2: think John Goodman stomping down with stiletto heels... or maybe don't think about that :(

    The cognitive dissonance here stems from the small size of bacteria- we aren't used to thinking in terms of the microscale.
  6. Feb 16, 2017 #5
    Ok, thanks. This answers my question.

    Let me ask a different question:

    Are these bacteria --lacto-bacillus species-- sensitive to light? Does it matter if I leave the jar out in the light or in the dark?
  7. Feb 21, 2017 #6

    jim mcnamara

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    Hmm. Light will not penetrate far into fermenting cabbage. Photoinhibition does occur in Lactobacillus spp. for some enzymatic processes. Answer: probably not very much. Use plastic or ceramic vessels if you are worried about it. You do not have to hide it away somewhere.

    Example showing photoinhibition of the manganese catalase enzyme:
  8. Feb 21, 2017 #7
    I have some 3 or 4 years old saurkraut in a gallon jar in the fridge. It has accumulated a lot of white stuff at the top and about 1/3 downwards. It still smells OK and I have heated and cooked it and it tastes good. Is the white just lots of the lactobacillus probably now dead.?? How long does it actually live? Its not mold. I like to experiment with fermented foods. If it smells OK, then its usually is. The nose seems to really analyze edibility very quickly. Tho certain things like limburger cheese are strange, my nose still said OK , you can eat it!
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