10 replies to this topic

[Sthembiso]

Hello Everyone, i am an inspector in a Domestic Quality Monitoring scheme and i have noticed that 80% of the results obtained (after sampling for certification purposes) for locally manufactured bottled water fail on aerobic plate count. The Zambian Standard requires that aerobic plate count is 10 maximum and i would normally get readings in the thousands. It is not accepted practice to give advice to establishments but i have had inquiries on how to control aerobic plate count (Feacal Coliforms and total Coliforms would in most cases not be detected) and would want to help in my personal capacity.

Is the 10 maximum too stringent and what exactly does aerobic plate count represent? Is it a critical food safety parameter?

Thanking everyone in advance

[Dr Ajay Shah]

For bottled water you should be testing for:

Heterotrophic colony count (HCC) which is the same as Aerobic Plate Counts(APC) or Standard Plate Counts and the maximum of 10 is reasonable. This comprises of dead and alive microrganims.

E.coli < 1 CFU/100ml
Coliforms < 1 CFU /100ml

If the Zambian standard says that it should be 10 then the commercial sectors should aim to follow that. The standard can only be changed by the Standards Commitee and this is can only be done by providing scientific evidence.

For water the critical parameters should be :

E. coli
Coliforms

I have already given the levels for which they should conform to.

I hope the above helps you. Other members may have different opinions.

Regards

Ajay

[DAVE84]

Usualy microbial content of water is controlled with the help of ozonization. Most of the bottled water company have a big ozonizer where they flush water with ozone gas. After water is exposed to ozone they hold water for 1 day (Do not know exact time) so that ozone in water gets disolved.

Hope this helps

Dave

[Sthembiso]

For bottled water you should be testing for:

Heterotrophic colony count (HCC) which is the same as Aerobic Plate Counts(APC) or Standard Plate Counts and the maximum of 10 is reasonable. This comprises of dead and alive microrganims.

E.coli < 1 CFU/100ml
Coliforms < 1 CFU /100ml

If the Zambian standard says that it should be 10 then the commercial sectors should aim to follow that. The standard can only be changed by the Standards Commitee and this is can only be done by providing scientific evidence.

For water the critical parameters should be :

E. coli
Coliforms



I have already given the levels for which they should conform to.

I hope the above helps you. Other members may have different opinions.

Regards

Ajay

Ajay,
Thanks for your comments. In my post i mentioned that Feacal Coliforms and Total would be according to the standard (as you have laid down) but the aerobic plate count would be in its thousand. So one thing i have gathered here is that the reading could be as a result of dead microorganisms and this being the case it means the water would still be fit for human consumption or am i assuming too much. Furthermore the critical parameters are feacal and total coliforms so for as long as the water meets the requirements of the two then it should be safe for drinking (and obviously it would have met all the chemical requirements such as minerals).

I think the way to go is to revise the standard and emphasise the need to have an Ozonator on the list of equipment. Thanks once again.

Stanley

[Carlos Leoncini]

Hi, TPC is an indicator that should be evaluated with other parameters including microbiology and physical and chemical analysis. Having TPC of thousands of cfu/ml is not a good sign. In my country 500 cfu/ml is required as maximum for bottling water. But regulations could change; you will have to meet your local regulation. It is important to find the source of the contamination. I don’t know Zambia but in S. Africa some domestic facilities do not use reservoir tanks. They process water come directly from municipality through pipes. That adds a degree of uncertainty and is difficult to control if you receive water out of spec. If you had a reservoir tank and TPC is the only out of spec parameter you could chlorinate and use carbon filtration to remove free chlorine and others. But be sure first about the source of contamination, the root cause. What are NO3 and NO2 values? What’s happening with E. coli and total coliforms values?

[Charles.C]

Dear Sthembiso,

The practical measurement of plate count is often expressed as “total viable count” in the context of the given growth media. Many “experts” also consider that use of the “fecal” terminology is now obsolete and preferably avoided (although it is still found in many locations).

There are whole books on the interpretation of water analytical data, including the items you mention, since many different approaches / analytical procedures exist. For example one standard text is “Standard Methods - For the Examination of Water and Wastewater”

Normally yr local standard will contain a reference to an appropriate sampling / measurement procedure and perhaps appropriate corrective actions based on non-compliance with the stated limits.

My initial comment on yr “thousands” would be that yr process (?) is faulty (eg contamination somewhere). The usual investigative route is to start from the source and follow the process steps.

Rgds / Charles.C

[Dinh key]

For control water

1. Control and check Origin water

2. Control the pipe piping and tank content: swabtest period, if contamination you must sterilizing by steam, or Oxonian, or chlorine,..

3. Water: can install UV lamp or ozonizer or micro filter,..

4. Control the empty bottle

Regards,
Dinh

[earthworminmysoup]

Generally water supplied to manufacturing plants is provided by local authorities or by springs. Local authority control the quality of water as prescribed in legislation, as all water has to be potable (wholesome).

I think I'm right in stating that bottled water regulations state that for TVC (TPC) the count should be less than 100 per ml on agar plated at 22 degrees and less than 20 per ml plated on agar at 37. So the first question is which temperature are you stating?

What is critical is that the water sampled has to be tested within 12 hours of bottling and kept refigerated if possible. If not then the natural microflora will obviousley multiply.

So any testing after this period really has no value on determining the quality of the water coming into the plant.

I think that 10cfu per ml is extremely tight for a specification, but it would be nice if all water could reach this level.

[siju]

Why the TPC is incubating at two different temperatures such as 22 and 37 degree celcius? Which method is better for getting satisfactory result whether membrane filtration or pour plate method? Whhether dead bacteria can form a colony like living bacteria on agar plates?
Is spread plate can be used for TPC test?



Sijo joseph
INDIA

Generally water supplied to manufacturing plants is provided by local authorities or by springs. Local authority control the quality of water as prescribed in legislation, as all water has to be potable (wholesome).

I think I'm right in stating that bottled water regulations state that for TVC (TPC) the count should be less than 100 per ml on agar plated at 22 degrees and less than 20 per ml plated on agar at 37. So the first question is which temperature are you stating?

What is critical is that the water sampled has to be tested within 12 hours of bottling and kept refigerated if possible. If not then the natural microflora will obviousley multiply.

So any testing after this period really has no value on determining the quality of the water coming into the plant.

I think that 10cfu per ml is extremely tight for a specification, but it would be nice if all water could reach this level.

[KTD]

Dear Siju -

Incubating at 22C gives an indication of total counts, while incubating at 37C gives an indication of the bacterial load potentially associated with animal contamination (entier, fecal, whatever you want to call it).
As far as monitoring procesures, consult AOAC for approved methodologies. Spread and pour plates are not normally accepted mentodologies due to the low counts you are trying to detect. There are several relatively easy to use membrane filtration kits out there.

[Charles.C]

Dear KTD,

Incubating at 22C gives an indication of total counts, while incubating at 37C gives an indication of the bacterial load potentially associated with animal contamination (entier, fecal, whatever you want to call it).

"Total" would seem to assume that water flora are dominated by psychrophilic species. Is this generally true ? (No idea since I hv never had the luxury of a cooled incubator so as to be able to run at 22 degC. )

Sufficient appplied chlorine (or a correct alternative process) will presumably give a near-zero result in both scenarios.

Rgds / Charles.C