We get many requests for information on “What microorganisms should I test for?” And even more for “What are the allowable levels of microorganisms in the product and in my facility?”. 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 programme.
In this first part of our two part series, we look at the what microorganisms should I test for and who says so. Part 2 will cover the maximum levels of microorganisms in your product and how often you should test for them.
What types of microorganisms should you test for?
There are 2 main ‘categories’ of microorganisms you will be testing for:
1. Food spoilage microorganisms. These are general microorganisms that do not cause classic food poisoning but do cause food to spoil or go off when present in too high a number. These tests will mainly consist of total bacterial counts also known as TVC (total viable count) and SPC (standard plate count). Yeast and Mould (Y&M) counts are also part of this group. Yeasts and moulds often result in food spoiling. These tests are important for the shelf life of the food. The lower the total number of bacteria, yeasts and moulds your food starts off with, the longer the shelf life will be, the fresher the food will taste, and the safer the food will be to eat.
2. Food poisoning bacteria – these are the bacteria which, if present in the food, may result in classic food poisoning such as vomiting, diarrhoea, fever etc., and in extreme cases, even death. These microorganisms are called pathogens or pathogenic micro-organisms. The most common food pathogens are:
- Salmonella spp.
- Staphylococcus aureus
- coli 0157:H7
- Bacillus cereus
- Listeria monocytogenes
- Pseudomonas aeruginosa
- Campylobacter spp.
- Vibrio spp.
- Clostridium perfringens
Where will you be able to find information on which microorganisms to test for?
- Firstly, you have to check if there are any legislated microbiological standards for the foods that you are producing. If there are any legislated standards, then you will need to make sure that, at the very least, you test against these standards. Please visit https://www.gov.za/search?search_query=Microbiological+standards+for+foodstuffs+and+related+matters for a view of the majority of legislated South African microbiological standards.
- If there are no legislated microbiological specifications for your food, you will need to do research on any recommended microorganisms to test for and what the limits are. This will depend on the type of food you are producing. Some foods are more prone to certain types of bacterial growth than others; for example Listeria monocytogenes outbreaks are not associated with dry maize meal and as such, would not routinely be tested for in dry maize meal; BUT, when it comes to processed meats, Listeria monocytogenes regularly causes food poisoning outbreaks, and would thus be tested with high frequency in processed meat. The following are possible sources for finding out what types of bacteria you should be testing for, as well as host of other food microbiology information:
- Your clients, whether another food company, or a retailer, may have specific microbiological testing requirements which you will need to comply to. Speak to your clients and determine if they have any specific requirements. Often large retailers or food manufacturers have entire food safety departments and may be a valuable source of information.
- Accredited food testing laboratories are another source of information. Speak to your food testing laboratory, who have qualified microbiologists working for them, and ask them for their advice.
Now that you know what micro-organisms you are going to test for, you need to decide what the limits of these micro-organisms should be in the food. The above references will also serve as a wealth of information on the microbiological specifications for your food.
Look out for part 2 where we will discuss the maximum allowable limits of
microorganisms in your product and how often you should be testing for them.
© Shane Rimmel of Food Consulting Services via Food Focus