06 Oct Reasons for Microbiological Testing
There are three types of microbiological criteria applied to testing:
Standards- A microbiological standard is a microbiological criterion that is a part of a law, ordinance, or administrative regulation. A standard is a mandatory criterion. Failure to comply with it constitutes violation of the regulation.
Guidelines- A microbiological guideline is a criterion that often is used by the food industry or a regulatory agency to monitor a manufacturing process. Guidelines function as alert mechanisms to signal whether microbiological conditions prevailing at critical control points or in the finished product are within the normal range.
Specifications- A microbiological specification is a microbiological criterion that is used as a purchase requirement whereby conformance with it becomes a condition of purchase between buyer and vendor of a food or ingredient. A microbiological specification can be either mandatory or advisory.
The acceptable range of microorganisms in food products depends on the food type. Results received need to be compared to the acceptable levels for your specific product dependent on which level of microbiological criteria you would adhere to (as per above).
To aid in this comparison it is advised that a product guideline of acceptable criteria is set up by the manufacturer for each product type. Clients that buy products from manufacturers may also provide guidelines for their suppliers. These guidelines must, at minimum, conform to legislation to ensure food safety.
The laboratory can give guidance on acceptable criteria. As each product differs with regards to acceptable criteria, it is advised to contact the laboratory with a specific query.
How are Samples Evaluated Using Dilutions?
Microchem’s testing policy and tariff permits for the analysis of only one dilution range, therefore it is essential to provide us with your product guidelines and criteria to which your sample should be analysed against. In this way we are able to provide you with results that are useful to you as a client. Additional dilutions can be accommodated with prior notification and will incur an added test cost.
Illustrated below is a dilution chart used to establish the most appropriate dilution to be prepared and plated in order to achieve the desired result range, as per the client’s microbiological criteria.
Table 1: Dilutions Ranges Applied To Enable Reporting Counts within Specified Ranges
*Note: Counts reported outside of the recommended countable range will be indicated as ‘estimated’ (E)
What does ‘<‘ and ‘>’ mean on a Report?
Below Lower Limit Count- ‘<’ will be used to indicate where no growth is detected at a dilution plated.
Where no growth is detected at a dilution of 1: 10 the result is <10 CFUs/g.
Where no growth is detected at a dilution of 1: 100 the result is <100 CFUs/g.
Where no growth is detected at a dilution of 1: 1 000 the result is <1 000 CFUs/g.
Above Upper Limit Count- ‘>’ will be used to indicate results which are too numerous to count (TNTC) at a dilution plated.
Where TNTC growth is detected at a dilution of 1: 10 the result is >3 000 CFUs/g.
Where TNTC growth is detected at a dilution of 1: 100 the result is >30 000 CFUs/g.
Where TNTC growth is detected at a dilution of 1: 1 000 the result is >300 000 CFUs/g.
In some cases a result might have an “E” next to the reported count. This essentially means the method advises that only counts within a recommended range be reported. If counts outside this recommended range are reported, this needs to be indicated. Microchem uses the ‘E’ to indicate when counts outside the recommended countable range are reported.
The countable range for TVC (Total Viable Count) is between 30 and 300 CFUs per dilution.
The results on the COA will read as follows for the following counts:
Average CFU count = 120 CFUs/g *120 is within countable range
COA Result = 120 CFUs/g
Average CFU count = 14 CFUs/g *14 is outside the countable range
COA Result = 14 E CFUs/g
Improvements on Reporting Results
Microchem has embarked to simplify and make our reports more user-friendly. In line with this we have removed the reporting of all presumptive tests and will only furnish the client with a final confirmed result on the report.
Other services by Microchem
- Routine Food Microbiology Analyses
- Food-borne Pathogen Analyses
- Water Microbiological Analyses
- Product Shelf-Life Analyses
- Hygiene Inspections and Reports
- Microbiological Swabbing
- Foreign Object Inspections
- Food Chemistry
- Nutritional Analyses
- Trace Elemental and Heavy Metal Analyses
- Food Colourants (Azo Dyes)
- Vitamin Analyses
- Water Chemical Analyses
- Melamine Analyses
- Pharmaceutical Analyses
Cape Town (Head Office)
1st Floor Fairweather House,
176 Sir Lowry Road
Woodstock, Cape Town, South Africa, 8001
Tel: +27 (21) 465-6996 or 061 394 1913
Micro Lab Cape Town:
Ilse Liedemann, email@example.com
Hannes Esterhuizen, firstname.lastname@example.org
Willem van Dalen, email@example.com
Gauteng Micro Laboratory
41 Golden Drive,
Morehill, Benoni, South Africa, 1501
Tel: +27 (11) 425-3775 or 061 393 5354
Hussein Ebrahim, firstname.lastname@example.org
Brendan Moore, email@example.com
Anna Tshwene, firstname.lastname@example.org
Please visit our website for additional information: www.microchem.co.za
We appreciate your understanding and are on hand for any assistance you may need.