Microbiology and food safety
According to the World Health Organisation, the contamination of food by microbial agents is a worldwide public health concern.
Most countries have recorded significant increases in the incidence of diseases caused by microorganisms in food over the past few decades.
Diarrhoeal diseases are the most common illnesses resulting from the consumption of contaminated food, causing 550 million people to fall ill and 230 000 deaths globally every year. In addition, diarrhoeal diseases may cause malnutrition and stunting, adding to the amount of Disability-Adjusted Life Years (DALYs) resulting from the consumption of contaminated food.
This is all preventable by implementing better food safety practices, both in food production and in home preparation and consumption.
The regulatory requirements for microbiological testing of food in Australia and New Zealand are laid out in the Food Standards Code, in Standard 1.6.1 (Microbiological limits in food) and in Schedule 27 (Microbiological limits in food)
Additional information and requirements for testing of ready to eat foods are provided in the FSANZ “Compendium of microbiological criteria for food”
It is important to note that food safety cannot be guaranteed by end product testing alone – therefore, the regulations are outcome based and require food producers to implement food safety plans based on HACCP principles to control identified food safety hazards in their processes (including microbiological hazards).
In addition to end product testing (as verification that HACCP controls are effective), food producers will also need to implement a systematic environmental monitoring (EM) plan.
The purpose of the EM plan is to provide advance warning that food safety controls are not working as required. Air quality and equipment swabbing can work together to identify possible areas of the facility that require additional attention during routine cleaning and sanitisation.
Some foods are higher risk for carrying pathogens than others and are termed ‘high risk’ or ‘potentially hazardous’ foods. They generally require a kill step or to be kept under temperature controlled conditions in order to be rendered safe for consumption.
The following list provides some key pathogens present in specific types of food and will help when establishing which pathogens to add to your routine testing program.
- Bacillus cereus: rice dishes (incl sushi); potato and pasta dishes; meat, vegetable and fish dishes (stews, curries etc)
- Campylobacter: undercooked poultry; raw meat; unpasteurised milk
- Clostridium perfringens: cooked meats (rolled or large joints); stews, gravies, curries and pies containing meat or vegetables
- Listeria monocytogenes: many foods support growth, including soft cheeses; deli meats; cooked chicken; smoked seafood; salads and rockmelon
- Salmonella: animal products (eggs, poultry, raw meat, dairy products; fresh produce (seed sprouts, melons, salads); low moisture foods (spices, peanut butter, chocolate and flour
- STEC (Shiga-toxin producing Escherichia coli): improperly cooked burgers; salamis; milk/cheese; fresh produce (leafy greens, sprouted seeds)
- Staphylococcus aureus: high protein, manually handled foods: meat/products; poultry/egg products; dairy products/milk; cream/custard filled bakery products; sandwich fillings
- Vibrio parahaemolyticus: fish, shellfish and crustaceans
HACCP and microbiology
The HACCP approach is a preventive approach to microbiological quality control and is intended to prevent problems before they occur rather than finding them in the finished product.
Hazard Analysis identifies the microbiological hazards and potential entry points of these hazards in the food production process. Critical Control Points to control the identified microbiological hazards include quality of raw ingredients, time/temperature relationships, sanitation and packaging control and the incorporation of additional barriers where required – such as pH and water activity management.
HACCP offers a more comprehensive and science-based alternative for controlling food safety hazards compared with traditional sanitation programs based upon good manufacturing practices. Controlling hazards under an HACCP program requires a systematic collection and interpretation of reliable data relating to the occurrence, elimination, prevention, and reduction of hazards.
These data need to be developed in a transparent environment that will ensure that the best scientific methodologies have been employed in developing the needed data. The two mechanisms used in HACCP to assess the adequacy of the database are validation studies and the verification assessments.
Microbiological testing is an important mechanism for collecting data used in developing and implementing an HACCP plan. Microbial sample data can help establish standard operating procedures (SOPs) for sanitation, assess the likelihood of the occurrence of hazards, establish critical limits, and assess the validity of the HACCP plan.
The use of a performance standard to assess whether microbiological hazards have been reduced to an acceptable level creates an especially important use for microbial analysis. Microbial testing is also useful in implementing an HACCP plan by helping to monitor the effectiveness of sanitation SOPs, the compliance of incoming ingredients with safety criteria, the safety of product being held for corrective action, and the safety of the finished product.
The verification audits demonstrate that all control measures have been applied as designed in the HACCP plan. Although auditing HACCP records is the primary means of verification, microbial sampling can play an important role as well.