what is the role of Enterococcus as cheese starter |
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Milkman
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Posted: 23 Mar 2010 at 10:03pm |
Some enterococci are quite heat resistant e.g to pasteurisation temperatures. This is the type of heat treatment used in the production of wpc powder. Hence if levels were high in the concentrate it would be reasonable to expect survivors in the powder.
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MrCage
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As I review the selective media for enterococcus it seems that enterococcus is more salt tolerent than typical coccus bugs. Often we think the the temperatures seen during final product drying is the final kill step. Now I wonder if the dry powder enviroment is the final kill step. But if enterococcus is salt tolerent would it have a better "survivability" compared to typical micro flora?
So if a hygiene problem and a heat tolerent/salt tolerent bug makes a nest this could result in elevated powder counts? |
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michael
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BTW I have updated the pages at http://www.dairyscience.info/probiotics.html and http://www.dairyscience.info/cheese-starters.html to reflect our discussions on enterococci. I have also added what I consider to be a very useful biochemical key for identifying enterococci, this is at http://www.dairyscience.info/entero-key.htm .
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Mike Mullan
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Sorry for delay in responding to your recent posts. Hopefully the responses from the other forum users have been helpful.
Riker2 has made a key point re microbial specification which I see you accept. Leading on from this you have to find where the enterococci are coming from and to control their levels. There are a range of options for doing this. You seem to be engaged in a testing process that will in time provide this information. I presume that this will also yield information on the effectiveness of UF plant cleaning. UF will concentrate any microorganisms present in whey and unless you have modified the UF process they will also probably grow during UF! Moving to enumeration. Enterococci typically grow in 6.5% NaCl, 40% bile salts and at pH 9.6. They grow at 10° and 45°C and can resist 30 min at 60°C . They are resistant to a range of chemicals some of which e.g. sodium azide can be used to produce selective media e.g. Slanetz and Bartley's medium. The use of 35° C for incubation will decrease the selectivity of this medium and give higher counts but I guess you know this? I personally would not focus on a particular Enterococcus species and would concentrate in reducing your enterococcus count. While some enterococci are used as starters and as probiotics their use in these applications is controversial; however, strain effects are very important in microbiology. The pathogens in this group are particularly 'nasty' causing a range of conditions including endocarditis and bacteremia. This is why high enterococcus counts are likely to be viewed with suspicion. I wish you well in your investigations and will keep this topic open. |
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MrCage
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This is the method our culture houses uses to test for enterococci.
Here is some info on the medium. It is called Slanetz and Bartley. We buy the already prepared plates. http://www.oxoid.com/UK/blue/prod_detail/prod_detail.asp?pr=CM0377&c=UK&lang=EN Our procedure is to plate 1 ml of chosen dilution over 5 plates (0.2ml per plate). Incubate at 35C for 48 hours. Count all colonies that are rust in color. Then perform an agglutination test to confirm Enterococci. The agglutination test for confirming enterococi is called the "PathoDx Strep D Kit" from Remel. |
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shark1
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I alos been followoing these posts. Hoping site owner will aslo reply to recent posts. What sort cheese r u making? Reading the materil from this site I see interesting things that i did not know before. How you know bugs not come from starter?
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MrCage
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Can't disagree with your opinion. Any thoughts on if Enterococcus is part of the natural milk flora of most dairy farms? Is it possible that only a few farms could deliver enough Enterococcus that could survive pasteurization(both milk and whey) and find a home in membranes on a daily basis and ultiamlty in product?
Or would it be more likely that a small number on Enterococcos found a home and over time multiplied in because of insuccient cleaning or foulent of membrane material? Thoughts? |
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riker2
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Interesting series of posts. You need to produce WPC to spec. High bug count needs to come down. You have a hygiene problem IMHO
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MrCage
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Thank you, great information. As I researched this bug I am seeing most concern with E. faecalis. Would you agree that this is the bug that I should look to identify if it is in our population in product?
Appears much work is being done on E. faecalis as an emerging pathgen. On the opposite end of the sprectrum Enterococcus ssp. are using for fermentations in meat and cheese....inteesting. |
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michael
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Enterococci are of concern for several reasons e.g.
human diseases, their resistance to many antibiotics, their ability to transfer antibiotic resistance genes and as indicators of fecal contamination. In microbiology it is always important to know what you are working with. For example fecal streptococci, also called Group D streptococci can sometimes be confused with enterococci. Enterococci are frequently isolated using a selective medium such as M-enterococcus agar or KF streptococcus agar. Agar containing bile-esculin-azide are often used for confirmation. Note some fecal streptococci may also grow on these media hence the need for confirmatory testing. Many entercococci and fecal streptococci are also fairly resistant to high temperatures. You might find some more useful information on tests by using Google Scholar. I regret I cannot recommend commercial ID tests-however there are definitely reliability issues with some! Your first approach should be to use a good selective agar media and follow up with simple confirmatory testing. This should give you a fair idea of concentrations. I noted that you mentioned MRS in your initial posting. Unless this has been supplemented with selective agents it would not be suitable for the selective isolation of enterococci. You might wish to consider contacting a dairy microbiologist from college/university/research institute for further advice. |
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MrCage
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We sent our powders out for "typing" by silikier. I am not sure of there method. What type of problems could enterococcus present? Thanks in advance.
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MrCage
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I see that VRW and Merck both have a host of Enterococci ID tests. Do you recommend any? Essentially we are looking to identify if a particular farm SPC population has more Enterococci than "normal".(although we don't know what normal is yet).
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michael
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Firstly a simple question, how do you know that they are enterococci?
If they are truly enterococci and are at high concentration then you may have a potential problem, not least if this is identified by any 'switched on' regulatory person or technical person from one of your buyers. |
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MrCage
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First timer to this site...impressive. As we "type" our SPC population in finsihed WPC we often find Enterococcus as the dominent bug on the SPC or MRS plate. I am certain that it is not starter but an enviromentmental survivor. Any other detail would be great.
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michael
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Enterococci are interesting. I do not have much more to add than your
excerpts from the cheese starter article on this site. They have been found in natural starters, artisanal starters and it can be argued that they should not be used as starters because some of them are pathogens and the antibiotic gene transfer problem. additionally they tend to produce high concentrations of amines. These can cause migraines- severe headaches often with visual disturbances. Others may have different views! |
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childream
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enterococcus have ability to exchange antibiotic resistance genes.
If they are more resistant to phage than lactococci? |
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childream
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It is the first time I hear about Enterococcus as cheese starter.
"Apart from their ability to grow at 45°C, at pH 9.6 and in the presence of high concentrations of salt they are similar to lactococci." but there is not DVI Entercoccus culture,and it is said that "they are present in some artisanal cultures and therefore, in practice, starters" so , I want to know what is the role of Enterococcus in cheesemking? If it is similar with lactococci, why add enterococcus? |
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