Staphylococcus and pH

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StefanS
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Staphylococcus and pH

Post by StefanS » Sun Dec 30, 2018 03:39

so I get confuse - dipper I dig then more confuse I got.. usually during our conversations we are taking that staphylococcus genome bacteria ( CNC - coagulase negative cocci)are very sensitive to pH. I have read that they are start to stop doing their work at pH 5.5, at pH 5.0 it is border line for their live... and with articles in "Meat Science" and example with Toldra statement (and other researchers) that LAB and Staphylococci are predominant bacterial flora in fermented salamis after fermentation (in some cases pH dropped to bellow 5.0) - is very confusing...
What are you think??
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redzed
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Post by redzed » Mon Dec 31, 2018 09:35

Stefan, where in Toldra's works does it state that the Staphylococcus bacteria continues to grow at a pH of <5? There are statements that S. Carnosus is can survive in a low acid environment, but that low acid environment is 5.2. And S. Xylosus is probably gone at 5.5. I've got a large number of articles on the subject and when I get some time I'll share my findings. But there are also other factors that are just as important. One study that tested 37 strains of Staphylococcus bacteria determined that all grew very well at temperatures between 20 and 30, but very little growth occurred at 10.
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Post by StefanS » Tue Jan 15, 2019 02:36

redzed wrote:Stefan, where in Toldra's works does it state that the Staphylococcus bacteria continues to grow at a pH of <5?
Chris - it can be misunderstanding - I do not stated that Staphylococcus grow below pH 5 - I stated that that bacteria is dominant (with LAB) in most of fermented sausages. (example - F. Toldra - Second edition of Handbook of fermented meat (chapter12.4.2 - p. 103). or example - Technological activities of Staphylococcus carnosus and Staphylococcus simulans strains isolated from fermented sausages
Meat Science, Volume 71, Issue 4, December 2005, Pages 643-650 (stating that they can grow at pH 5.0 but at that level do not produce histamine)
or example - Characterization of Micrococcaceae isolated from Iberian dry-cured sausages
Meat Science, Volume 75, Issue 4, April 2007, Pages 696-708 - stating - All the investigated strains (Staphylococcus ) -were able to grow at pH and aw greater than 5.0 and 0.85, respectively, the values usually found in Iberian dry-cured.
above are some of examples -
So I know that there are a few more factors but also some of these factors having affect that we should consider that Staphylococci can produce lactic acid as well other acids too. (it is suicide?? )
Any way - IMO - it is different environmental in salami mince affecting grow of bacteria (some of them aren't known yet) and laboratory environmental on agar plate. I will keep my mind open that GNC cannot survive pH below 5.0 but with question mark.
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Post by redzed » Mon Jan 28, 2019 03:10

Stefan, I won't be home for another week, and unable to access my digital library. I'll look at your references when I return home and have some time. Regarding your question about Staphylococcus bacteria producing lactic acid, I'll look into it, but from what I remember reading somewhere is that this bacteria does lower the pH, however slightly, but through a different process and not fermentation.

And Staph. bacteria will survive below 5, but just will not grow and will therefore be quite useless. These are really good questions for someone from the starter culture industry. Specific bacteria can greatly differ by strain, so it may be incorrect to make a blanket statement that they do dor't survive at a pH of 5.
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