6 replies to this topic

[Simon]

I've posted this topic for new member Lalith Gunatillake. He would like to know the best methods for detection of E. Coli in food additives (A powder).

Can anybody help?

Regards,
Simon

[cazyncymru]

I've posted this topic for new member Lalith Gunatillake. He would like to know the best methods for detection of E. Coli in food additives (A powder).

Can anybody help?

Regards,
Simon

i'm not sure where you are Lalith and how much money you'd like to spend, but here are some pointers

you could reconstitute powder and plate onto vrbga. confirm any counts onto tbx agar. you'd need to work out your dilution but i'd suggest a 1/10 reconstitution in mrd or ringers.

or you can look at e coli petrifilm, a bit more costly, but no need to make up agar and no petri dishes.

or if you have loads of bucks you could look at a microfoss (which we're going to buy if i get my way!)

if you need further details, like contact details or the test method for traditional plating let me know and ill post on here for you

[Charles.C]

Dear Lalith,

Did you mean E.coli in general or more specific such as the pathogenic O157.. variety ?
As Caz states, money (and speed) can sometimes be relevant.
Never worked with food additives however I agree Caz that petrifilm is nice and easy (but not cheap) however IMEX it will also depend on yr spec. / levels which are presumably low (eg ), Lalith is here - http://www.ifsqn.com...amp;#entry15934

[Lalith Gunatillake]

Dear Charles and Caz,First thanks for your comments. Yes I need E.coli in general. I think if E.coli is absent in general in our product that much confirmation is enough for customer. Anyway I am not a Microbiologist so tel me somthing about this pathogenic O157.. variety. Is it important to look separatly?

Thaugh Thaumatin is a powder it is highly soluble in water and is a sweet tasting protein (Freeze Dried). So we can make it to a solution for testing. Redymade petriplates that you mentioned, is it same as in VWR Nutrient pads (Cat no 54505 1N). I have alredy ordered this. I need some more details about a plating method which is accepted internationally for detection of E. coli.
Thanks
Lalith Gunatillake

[Charles.C]

Dear Lalith,
The options will depend somewhat on whether you wish to measure E.coli levels or only get a presence/absence result. The following assumes the former.
Petrifilm E.coli plates (AOAC validated technique [but not sure for food additives]) are described here –
http://solutions.3m....s/e-coli-count/
and here http://www.carolina......coli Coli.pdf
(The detailed procedures are in AOAC manual amongst others)
The usual plate limitation is that the minimum result is 1 colony which corresponds to 10/g if dilution starts at 10exp(-1). So if yr spec. or objective is more strict than that, you need to use MPN techniques (or use multiplate methods which gets expensive). Personally I prefer conventional MPN liquid media systems based on BAM so as to get lower detection level than above but these are usually slower and require more equipment, eg -
http://www.cfsan.fda...ebam/bam-4.html
The pathogenic varieties of E.coil are discussed here –
http://www.cfsan.fda...bam/bam-4a.html
and here
http://www.cfsan.fda...mow/chap15.html
Sorry, no experience vwr nutrient pads, is this a validated technique?
Rgds / Charles.C

[cazyncymru]

Dear Lalith,

Did you mean E.coli in general or more specific such as the pathogenic O157.. variety ?
As Caz states, money (and speed) can sometimes be relevant.
Never worked with food additives however I agree Caz that petrifilm is nice and easy (but not cheap) however IMEX it will also depend on yr spec. / levels which are presumably low (eg ), Lalith is here - http://www.ifsqn.com...amp;#entry15934

in the food industry (Dairy) we have used VRBGA and confirmed any positives on TBX.
It is time consuming and is ok if you have a long shelf life product ( by time consuming i mean a couple of days!)

we've moved over to 3m's petrifilm as we can get results quicker ( i think 24 hours)

we're now looking at purchasing a MicroFoss which will give us results in 15 hours, which is what we need for a short shelf life product.

Both the VRBGA and TBX methods are British Standard methods

c x

ps i'm in wales on a secondment looking at BRC for a factory we've bought, and doing my day job too!!

[Lalith Gunatillake]

Dear Charles and Caz, Thanks for comments. Sorry I also don't have exp in nutrient pads. Ones I receive I will let you know how it is.