[George Howlett]

I’ve noticed in many of the forum threads the recurring theme of risk assessment. Questions such as how best to identify hazards, determine whether hazards are important or significant and where to find information on hazards? In particular microbiological hazards present the most difficulty since many of us who are charged with the responsibility of hazard analysis and HACCP planning are not microbiologists and when we find information on the subject we may not always be in the position to interpret it correctly.

The evolution of risk based food safety systems such as HACCP have played a major role in protecting public health and underpinning our efforts in a structured and scientific way. However the practical impact on those in our industry who are required to develop these systems is significant and often characterised by what we don’t know rather than what we do.

There is a well-documented Salmonella case were a food business producing salami products decided to develop a snack version which was smaller and had a higher mass to surface area ratio. The product dried out faster, water activity fell faster and acidity was incomplete. This gave rise to favourable conditions for Salmonella and a recall was required.

The above account highlights the difficulty with microbiological risk assessment (MRA) as part of HACCP. The simple act of producing a smaller version of the same product led to a microbiological hazard that previously did not exist. It also indicates the knowledge required to conduct proper hazard identification.
Much has been written on the subject by experts trying to understand why HACCP plans fail and lead to recalls. Research reviewed by Kane, Mayes & Mortimore identified poor hazard identification and hazard analysis as a significant reason. So how do we conduct microbiological risk assessment in food processing plants? How do we ensure that our risk assessments are robust enough to support our HACCP plans and reduce the chance of product failures?

In the next series of threads I will provide some practical support and resources for conducting MRA. It is not an easy topic to address yet it is an essential part of what we do as people responsible for food safety. Please contribute to the thread and add your own insight and advice.

There are 4 main steps in conducting a Microbiological Risk Assessment:

• Hazard Identification
• Hazard Characterisation
• Exposure Assessment
• Risk Characterisation

These steps have been defined by bodies such as the WHO/FAO and bearing in mind that no food processing plant has the massive resources of these bodies, we can use simple tools to conduct a good quality MRA depending the complexity of your products and processes. In the next thread we will look at the first step, Hazard Identification.

[George Howlett]

STEP 1 - Hazard Identification

This is the first step in conducting microbiological risk assessment and perhaps the most important since if you don’t identify the hazards correctly no amount of subsequent HACCP planning will make your product safe.

The purpose of hazard identification is to identify the microorganism(s) of concern that may be present in the food you manufacture.
While on the face of it this may appear to be straight forward it can often prove to be difficult without expertise. Assuming you do not have a massive budget to employ the services of a microbiologist you will need to undertake this process yourself. Nor should you depend solely on the senior microbiologist in your external testing laboratory who may not be fully knowledgeable on all aspects of your product and processes.

The hazards of concern may come from a variety of sources including:

• Raw materials
• Methods of production
• Use of the food

In short you are looking to generate a list of potential microorganism that may have adverse impacts on human health should they be present in the food. And to do this you need Information. Remember this takes time but the effort will stand you in good stead and your HACCP will be all the better for it. There is a wealth of information available on food hazards and much of it is available free from quality sources on the internet. I have put together a list of some of the main sources for you in this excel workbook – just click the links and start your research.

 Risk Assessment Data Sources.xls (33.5K)
Number of downloads: 301

For example the Bag Bug Book provides excellent information of specific pathogens including details on associated food products and outbreaks.
Foodrisk.org contains a good database of food hazards organised according to commodities. The database can be easily searched.

Once you have compiled your list of potential microorganisms you now need to decide whether they are significant and require more detailed analysis (Step 2: Hazard Characterisation). To do this you will need to apply a series of logical questions which can come in the form of a decision tree not unlike that found in HACCP. However these questions are very specific for microorganisms and more robust than the generic ones found in the 4 question HACCP decision tree. I have attached a template of this decision tree which I have adapted from P. Vosey et al.

 Hazard Identification Decision Tree.doc (75.5K)
Number of downloads: 203

Work your way through the questions until you have developed your final list of pathogens. Don’t forget to keep a copy of all your work and reference sources for the auditor when he/she arrives.

Just one final point. The key to Hazard Identification is to review as much information and data as possible. You can do this over time and build up you own data bank of information. The more you know the better your risk assessment and resulting HACCP system will be. None of this time will be wasted.

In the next thread we will look at STEP 2 – Hazard Characterisation.

George.

[Charles.C]

Hi and Warm Welcome George,

Thks for the links and this interesting template, and particularly the series of "how to's".

Certainly not an easy challenge to analyse/segregate pathogenic micro-organisms in a template way.

Not trying to nitpick but a few comments came to mind –

(1) The (2nd) No. 5 is presumably No.6
(2) I deduce the template assumes that the process environment is not a contamination factor ?
(3) The template seems to assume that the raw material does not contain a toxinogenic pathogen at a level such that the relevant toxin may have already been produced prior to processsing. Such a situation would relate to the use of Qu6 perhaps.
(4) Qu.2 might perhaps hv acknowledged some common nasties, eg “vegetative phgs / spore formers / toxins”. (I appreciate that the intention is to offer a minimalist structure.)
(5) Qu.3 – I’m slightly confused. Surely the product is already “contaminated” by definition or perhaps the question is to a specific meaning of “contamination”, eg actual level, legislatory ?

Some of the above may hv been scheduled to be addressed in subsequent articles in which case my apologies for jumping in too quick.

“Unfectious” sounds suspiciously Irish even though Google gives a Scottish example from the 1800’s.

Best Rgds / Charles.C

[Peter Snopko]

Great discussion item. I like the simple approach and resource referencecs for a Packaging person like myself.

Is there any chance you can also make references to packaging manufacture, as this is my core focus. I have been looking for a nice Idiots guide to "Pathogen Management Risk Assessment".

Looking forward to the next installment
Cheers
Peter

[George Howlett]

Charles.C, on 11 May 2011 - 07:14 AM, said:

Hi and Warm Welcome George,

Thks for the links and this interesting template, and particularly the series of "how to's".

Certainly not an easy challenge to analyse/segregate pathogenic micro-organisms in a template way.

Not trying to nitpick but a few comments came to mind –

(1) The (2nd) No. 5 is presumably No.6
(2) I deduce the template assumes that the process environment is not a contamination factor ?
(3) The template seems to assume that the raw material does not contain a toxinogenic pathogen at a level such that the relevant toxin may have already been produced prior to processsing. Such a situation would relate to the use of Qu6 perhaps.
(4) Qu.2 might perhaps hv acknowledged some common nasties, eg “vegetative phgs / spore formers / toxins”. (I appreciate that the intention is to offer a minimalist structure.)
(5) Qu.3 – I’m slightly confused. Surely the product is already “contaminated” by definition or perhaps the question is to a specific meaning of “contamination”, eg actual level, legislatory ?

Some of the above may hv been scheduled to be addressed in subsequent articles in which case my apologies for jumping in too quick.

“Unfectious” sounds suspiciously Irish even though Google gives a Scottish example from the 1800’s.

Best Rgds / Charles.C

Thanks Charles,

You are of course correct. The model is not intended to be an exhaustive risk assessment but rather a simple filter of the main pathogens with a view to conducting a more detailed assessment on the main suspects. Factors such as exposure and other routes of contamination are addressed in later steps. Question 3 for example is addressing the potential of contamination after processing i.e. a lethal control step as opposed to the raw material as a source.

Feel free to adapt the model further and improve upon it. It would be great to produce a collaborative guide for members when the post is complete?

Cheers!

[George Howlett]

Peter Snopko, on 11 May 2011 - 09:57 PM, said:

Great discussion item. I like the simple approach and resource referencecs for a Packaging person like myself.

Is there any chance you can also make references to packaging manufacture, as this is my core focus. I have been looking for a nice Idiots guide to "Pathogen Management Risk Assessment".

Looking forward to the next installment
Cheers
Peter

Hi Peter

Thanks. The discussion is currently focused around the assessment of pathogenic risks in a food matrix. But I can identify with your requested. In a previous life I was responsible for quality and hazard management in a PET moulding company and always struggled to find good source data on this area. I suppose because the risks may be less or somewhat unknown this area gets less attention.

I'll do my best be make reference to packaging if possible or maybe we can come back to this as a discussion topic at a later date. I'm working on STEP 2 at the moment and hope to post it later this evening.

George

[George Howlett]

STEP 2 – HAZARD CHARACTERISATION

Once you have identified the specific pathogens of concern the next step is hazard characterisation. This should be conducted for each pathogen identified.

In its simplest terms, hazard characterisation is an assessment of the pathogen and the nature of the problems it can cause. We are trying to answer a number of questions in order to develop the character of the hazard. These questions include;

• What is the disease caused by the pathogen?
• What are the symptoms and how long before their onset?
• What are the range and likelihood of adverse outcomes e.g. death?
• What is the minimum dose required to produce symptoms?
• Who are the main 'at risk' groups in the population?

To answer these questions you will need good sources of information. Remember, this data may not always be available so there will likely be a degree of uncertainty with your answers. This is unavoidable, however what is important is that you identify this uncertainty.

The New Zealand Food Safety Authority has produced some excellent datasheets on the main food pathogens where you will find much of the information required for hazard characterisation. The image below is part of the datasheet for E.Coli O157. By way of an example, I have highlighted some sections relevant to hazard characterisation.

 E Coli Datasheet.JPG (247.6K)
Number of downloads: 73


You can view the full list of datasheets here: New Zealand Food Safety Authority - Microbiological Data Sheets


An important concept of hazard characterisation is ‘Dose-response’. This is the minimum level of the pathogen required to be ingested to cause an adverse response e.g. 10 cells. Again, this information can be found in the above mentioned data sheets.

I have prepared a MRA model using Excel. It is based on a variety of sources and tools that I have referenced. It can be used to capture and score the required questions. The model contains all the steps required for good quality risk assessment with the final total score providing a measure of the risk. The model is easy enough to work with but any questions let me know. I will address the remaining steps of MRA in the coming days.

 MRA Profiling.xlsx (70.68K)
Number of downloads: 127
 MRA Profiling (Excel 97-2003).xls (109K)
Number of downloads: 48


George

[George Howlett]

STEP 3 - EXPOSURE ASSESSMENT

In the previous two steps we a) identified the likely hazards of concern and b) characterised these hazards in terms of the dose and response. When conducting a microbiological risk assessment the next step is exposure assessment.

The aim of exposure assessment is to determine the level of the microorganism (or toxin) likely to present in the food at the time of consumption. Here we must take into account a number of potenital paths or routes of contamination and the impact of various processing steps on microbiologcal levels. The following are important:

• The microbiology of the raw material e.g. raw meat will have certain pathogens associated with it.
• Initial contamination levels of raw materials.
• The effects of production, processing, handling etc on the levels of pathogens in the final product.
• Sanitation standards in your processing plant.
• Potential for re-contamination after a specific control point e.g. cooking.
• Characteristics of the food being produced.
• Product usage and instructions.

Data required to conduct Exposure Assessment may be found from the following:

• Pathogen data sheets (see previous posts for references)
• In house micro testing reports and history.
• Outbreak data.
• Complaints data.
• Guides, standards and codes of practices.
• Micro modelling, challenge testing etc.

The Hazard Identification Decision Tree provided in the previous post gives you a structured approach to the above and ensures you cover all the exposure paths. You use a scoring system to reflect your assessment and the sum of your score provides you with an assessment of risk.

While a score is applied to your answer this does not mean your MRA is quantitative. It is in reality a qualitative risk assessment since only large agencies and research centres have the resources to conduct full quantitative MRA's. Also be aware that uncertainty in risk assessments is as important as what you know. Don't be scared to document any uncertainty and be open about it i.e. 'there is not enough available data to conduct a clear assessment...' Understanding the uncertainty allows you to be more cautious on certain aspects of the process.

STEP 4 - RISK CHARACTERISATION

This is the final step and is basically the total score produced at the bottom of the Excel model. It is the measure or character of the risk as assessed by you.

Microbiological Risk Assessment like HACCP and food safety management in general requires good quality data. I am currently working on a more comprehensive database of hazard reference sources from the web which I will post before the end of the week.

Please come back to the forum with any questions or clarifications you might have.

George.