Article by Dr Roy Betts, Head of Microbiology, Campden BRI

Although food safety assurance is now most often achieved through risk assessment and risk management via well designed HACCP procedures, testing still forms a key part of any food production system. Test results give indications of on-going raw material quality, of food production environment hygiene, act as verification within HACCP systems, and are a key part of any manufacturers due diligence system.

The time it takes to obtain results is a one of the major issues associated with microbiological testing. Traditional microbiological test methods, such as those specified in most national and international standards, require microorganisms to be grown in broths or agars before detection or enumeration can be carried out. As growth takes many hours, it’s not unusual for a microbiological test to take from one to seven days to give a result. Decisions can ride on test results so speed is important.

A range of research and commercial organisations have been looking into the provision of rapid microbiological tests for foods for decades. The ideal solution will provide results for some key microbiological analytes much more quickly than traditional tests.

Numerous rapid tests are available for a range of microbial types. There are systems that simply make a test easier to perform in the laboratory by producing pre-prepared count plates. Some systems are highly automated to allow a greater sample throughput for laboratories handling large numbers of samples per day, and there are methods that use the latest biochemical and molecular systems which considerably reduce incubation times and therefore deliver results much faster. Rather than go through a long list of the various tests that are available, in this article I’d like to concentrate on how to make a more general decision on which test is right for your laboratory.

To choose a method that is right for you, the first step is to carefully analyse what you do now and how you’d like to improve it. Then anticipate what sort of tests in what quantities you will be doing in one to five years time. This forms the basis of the decision making process. You then need to answer some fundamental questions:

1) What do you need to test for? Pathogens, indicators, spoilage organisms? Do you need a rapid method for them all? This will indicate if you can use one method for everything or if you need a range of methods to cover all the analyses that you want to do.

2) How many tests will you do per day? How many samples will you handle? Do you have any constraints on staff numbers or laboratory space? This will help you decide what type of test automation you may require. Is a fully manual test suitable for you, or do you need full automation that can handle tens or hundreds of samples to be tested per day with minimal staff input?

3) How fast do you want results? You may need to speak with your clients to see what their need is. But remember, faster results usually come at a cost. Will your client be willing to pay more for a faster result?

4) What skill level is required for a new test? Are you prepared to use highly skilled staff to carry out a test or interpret a result? Or do you need a “black box” type test where samples are entered at one end and a final result is issued from the other?

5) What are you willing to spend on specialist equipment in order to do a new test? Some methods require a very large outlay on capital equipment - others may require very little.

6) What consumable cost are you (and your clients) willing to accept? Some of the more technical methods require relatively expensive consumables that drive up the cost per test. However, these costs may be acceptable if it reduces product quarantine periods and reduces the need for warehousing.

7) What are the servicing/calibration costs for the new method? This can be a hidden cost that is often never considered until a method is in use. Most methods based on equipment will require that equipment to be serviced and calibrated at least annually, particularly if the method is part of an accredited test. Service costs can be expensive. Also check that the method supplier is able to provide servicing and backup to you, should the method give you problems.

8) Will the method work? Will it give you accurate results? The best way to consider this is to look at whether the method is validated and certified by an independent third party. There is an International Standard that covers the validation of microbiological methods. ISO 16140-2 provides a system for the independent validation of microbiological test methods, giving potential users confidence that methods do give equivalent results to standard methods. Check whether the method has been validated and certified to that ISO standard. Organisations such as MicroVal will organise such validations and certifications, and expert validation laboratories such as Campden BRI will do the independent testing. Following this, laboratories will have to do their own internal method verification tests to ensure any method works in their hands.

9) Acceptability of the method. Perhaps this should be first on the list because it is critical that any method is acceptable to those who use the results. Is the method allowed within legislation? Does it meet your client specifications? A laboratory must take into account if legislation or specifications only allow a particular named method to be used or if a method is not permitted.

These nine points are a starting point if you are considering implementing potential new methods. But before trying to implement anything, you must do considerable work to establish if a method will do what you want it to do. By taking a careful, structured approach, your laboratory can develop excellent new methods that help you to deliver high quality and fast test results to your clients.

About the author: As Head of Microbiology at Campden BRI, Dr. Roy Betts currently manages a large team of scientists and technicians and is a recognised expert in food microbiology and related issues having developed the research area of rapid methods, giving Campden BRI an international reputation as a scientific centre of excellence within the microbiological field.