Setting up a microbiological testing program for your food products - Part 2

By Shane Rimmel of Food Consulting Services on 11 June 2019

In many cases detecting the presence or confirming the absence of a microorganisms is not enough. Some microorganisms require relatively high numbers to make you sick while others only require a few to result in the symptoms if ingested.

When testing your food for microorganisms it is important to understand what microorganisms you should be testing for; what the specifications for these microorganisms should be, and finally, how frequently one should be performing the various tests. Only once all of this is known, can you successfully design and set up an effective microbiological testing program.


In Part 1 of this series we discussed what microorganisms you should consider testing for, the reasons for this and then we touched on the reasons for why these microorganisms should be considered.


In many cases detecting the presence or confirming the absence of a microorganisms I not enough. Some microorganisms require relatively high numbers to make you sick while others only require a few to result in the symptoms if ingested.


What are the limits or specifications for the micro-organisms you are testing for?

Different foods will have different guidelines or specifications for the limits of microorganisms. It is important that you find out the correct specifications for the type of product you are producing. You can check for any legislated guidelines or do research to determine the limits. As previously discussed, you can also speak to your clients and accredited food testing laboratories.

  • In terms of food spoilage bacteria, the limits will depend on the type of food. Pasteurised fresh milk may be allowed up to 50 000 cfu/ml of total general bacteria, whereas canned vegetables or UHT milk need to be sterile and any bacteria are not acceptable.
  • With regards to pathogenic bacteria, most ready to eat foods will have zero tolerance for pathogens. Raw foods however, especially raw meat and chicken, may allow limits of certain pathogens. Raw red meat may have up to 1000cfu/g of coli and up to 100cfu/g of S.aureus.

Now that you know which micro-organisms you will be testing for, and what their limits in the food are, we need to decide how frequently we will perform the testing.

Food Consulting Services

Setting up the testing schedule frequency – how often should you be testing for which bacteria?

You need to determine the frequency of testing based on various risks within your manufacturing process. If you test all the food produced, there will be nothing left to sell!

The frequency of testing will largely depend on a combination of the following risk factors:

  • The ease of bacterial growth in the food being produced – bacteria find it difficult to grow in dry foods such as rice, maize meal etc. due to their low moisture levels, and these foods would thus generally be tested less frequently than moist perishable foods, such as ready to eat chicken sandwiches, in which bacteria can easily grow. Microorganisms generally find it difficult to grow in foods which are very dry, very salty, very oily, very sugary or very acidic.

  • Raw versus ready-to-eat food – Raw foods that still need to be cooked may require less frequent testing as they will still be cooked, which will kill many of the bacteria. Ready-to-eat foods, such prepared salads, will not be cooked and whatever bacteria are in the salad, will end up affecting the customer. These foods may require more frequent testing.

  • Food safety assurance of raw materials suppliers – if your raw material suppliers all have food safety systems in place and provide COA’s with each batch of raw material, testing can be less frequent than if suppliers with no, or unknown food safety systems in place, are used. The safer the raw materials of your food the less frequent the testing can be.

  • Requirements of your clients - Your clients purchasing your food may require a certain testing frequency, and as such, you will need to comply to your client’s requirements, whatever they may be. If you are marketing food to any vulnerable population groups (e.g. baby milk formula), your testing frequency will increase and should ultimately be each batch.

  • Batch release testing versus testing to prove compliance: Some foods, usually with long shelf lives (e.g. canned food) can be tested first, and only after microbiological results prove they comply, are they released into trade. Foods with short shelf lives, e.g. prepared fruit salad, cannot wait for test results before they are released into trade as they may expire before the results are even available! For foods with very short shelf lives, one cannot do batch release testing, and the testing records will serve to prove historical compliance to food safety standards.

  • Availability of historical food test results – If you are just starting off a food company, or are releasing a new food line, more frequent testing of the food would be required, as there are no prior results to prove compliance. The test results would serve to detect and correct any initial problems. Once testing has been conducted for a few months and all the results prove compliance, the frequency of testing could be reduced. The more your tests prove your food is compliant, the less your frequency of testing can be. The more problems you pick up with your foods, the more frequent your testing should be.

  • Detection of microbiological problems - If a problem is detected during routine testing, then testing may need to become more frequent until such time that it can be proved that the problem has been resolved. If a general food industry microbiological problem is being detected in the food category you operate in (such as the Listeria monocytogenes outbreak in the processed meat sector in 2018) you will need to increase the frequency of testing to ensure that you are not part of the problem.

  • Your food safety management program – if your food factory has a very effective and well managed food safety management program in place, your testing frequency may reduced.

  • Food testing budget allocation - in the ideal world money would not matter, however budgetary constraints are a reality of any business. Testing a sample of each batch would be the ideal situation, but may not be possible based on budget, nor even necessary, based on risk. Based on all the information above, a testing schedule should be developed and then the budget developed around this testing schedule.



Developing an effective microbiological testing program for your foods does require research to determine which bacteria you should be testing for, and what specifications you should be using.


Understanding how often you should be testing your food requires that you take the various unique risk factors for your factory and food into account. The higher your overall risk of microbiological growth and contamination, the more frequent your testing should be and visa versa.


Once you have all the above relevant information, you will be able to develop an effective microbiological testing program that will ensure that you are able to provide a safe food to your customer.



About the Author:

Shane Rimmel is Director at Food Consulting Services.

To view the services they offer, visit: 


Related Articles

Setting up a microbiological testing program for your food products

By Shane Rimmel of Food Consulting Services on 26 May 2019
We get many requests for information on “What microorganisms should I test for?” and “What are the allowable levels of microorganisms in the product a...

Read more