Product and Ingredient testing

Northern Hygiene Laboratories Ltd is UKAS accredited for the testing of foods for bacteria across a wide range of products and liquids. These include finished products, ingredients and work in progress.

Microbiological tests basically fall into three categories, these are:

• Indicators of overall quality and spoilage.
• Faecal indicators.
• Specific food poisoning

Normally a testing regime is based on these three categories of bacteria. When it comes to faecal indicators and food poisoning bacteria the specific ones tested for will depend on the type of products you produce. For example, the bacteria tested for in meat samples vary significantly from those tested for in fruit juices.

Testing procedures and the time taken for the test vary and, in the case of the latter, times range from 24 hours for coliforms to five days for yeasts and moulds. Thus, defining your testing needs is not simple but we are here to help you.

Total Aerobic Colony Count

All the bacteria present in a sample give an overall indication of the conditions of production and keeping quality. This is known as the Total Viable Count.

Coliforms & enterobacteriaceae

These are important faecal indicators that indicate faecal contamination and the potential presence of other faecal organisms such as salmonella.

B Glucuronidase Positive E. coli

The main faecal indicator that reflects the presence of mammalian faecal contamination.

Coagulase Positive Staphylococcus

An important food poisoning micro-organism that is commonly found in infected sores and cuts on staff.

Clostridium perfringens

A spore-forming food poisoning organism that is classically associated with reheated meat dishes.

Salmonella spp

The well known food poisoning organism that is associated with many different types of food, including meat, dairy products and vegetables.

Listeria spp

Another important food poisoning organism that has been associated with pàté, coleslaw, sandwich fillings, soft cheeses and other specific foods.

Bacillus cereus

A classic food poisoning bacterium that primarily was associated with rice based dishes and is now being seen more in pasta based products.

Campylobacter

The 'new' food poisoning organism that is often associated with poultry products but is more widely spread and receiving more media coverage.

Vibrio parahaemolyticus (*not UKAS accredited)

Not so commonly found, but this bacterium has been associated with some meats and, more importantly, fish and fish products.

E. coli 0157 (*not UKAS accredited)

The real killer that has been associated with several major food poisoning incidents with mortalities. Detected by specialised tests that we provide.

Yeasts & moulds

Spoilage organisms in a wide range of products including soft fruits, meats and chilled foods.

Lactic Acid Bacteria

This group of organisms could cause spoilage in food, especially in vacuum packaging.

Pseudomonas

Another food spoilage organism often associated with spoilage in fish products but can also be found in meat. They are found in the environment, in soil and water.

Enterococci

A group of organisms found in the faeces of most humans and many animals, they are used as a marker of faecal contamination in food products.

Shelf-life testing of products

Shelf-life testing is a procedure that helps to predict the microbiological status of a product throughout, and at the end of, its shelf-life, that is the time when it is in the hands of the customer and, finally, the consumer.

If the shelf-life evaluation indicates that at its use by date a product is microbiologically acceptable then we can say for future products that, if they have a similar bacterial burden at the time of production and are handled in a similar way throughout their lives, they should have a similar status to the tested product at the end of their shelf-life.

This then gives you, and your customers, more confidence in the product and can also be an important part of any due diligence defence should a problem arise. Shelf-life testing thus involves mimicking the way the product is handled in the real world and determining the effects of this on its bacterial population.

Different products behave in different ways and, for this reason, each time you have a new product or modify an existing one it is prudent to undertake a shelf-life determination.

It should be noted that the word product should be taken in the broadest sense. So, a product changes if its recipe or ingredient source(s) change, but it also changes if the type of packing or controlled atmosphere in the pack changes. Shelf-life trials require careful planning and this should take into account the needs of yourself and your customer.

It should also be remembered that a trial product made in the product development stages can vary significantly from the same product when it is produced on a commercial scale.

Obviously, shelf-life evaluations will be undertaken at the product development stage, but it is also prudent to repeat them in commercial production to confirm no significant changes have occurred.

Microbiological testing of water

The important role of a safe drinking water supply in public health has been appreciated since the 19th Century. In the 21st Century it is now just as important, if not more so.

In more recent times the importance of water quality in the processing of foods has become a bigger issue and today legislation actually requires certain food operations to test their water supply to confirm it is of an acceptable microbiological quality.

It is accepted that a single water test can not guarantee the status of a water supply and that regular testing is, therefore, essential. However, this can be done by relatively simple tests at reasonable cost.

Basic water testing

Total coliforms, which are indicative of faecal contamination, should not be present in a treated water supply.

In addition, total viable counts should be undertaken as an indication of the overall microbiological quality of the water supply. Different types of water have different total viable count standards and any significant changes from these, either suddenly or as a trend over a period of time, should be regarded as unacceptable.

Total counts are undertaken at incubation temperatures of 22 and 37°C so that they encompass the full range of bacteria likely to be present.

Typically, water samples should be tested for their total viable count, at 22 and 37°C, and for coliforms and E. coli. In specific situations testing for other bacteria such as faecal streptococci, Clostridium perfringens, pseudomonas and salmonella may be appropriate.

Testing procedures

Testing procedures vary and are often dependent on legislative requirements or industry sector practices. The two main methods used at Northern Hygiene Laboratories Ltd are

• Direct Plating Methods
  These involve plating 1.0ml of water directly on to the appropriate agars and counting the number of resulting colonies. Results are recorded as 'per ml'
• Membrane Filtration Methods
  These involve filtering a predetermined volume of water through a microbiological filter and then determining the number of bacteria on the filter. Results are recorded as 'per 100ml' or relative to the volume of water filtered.

Hygiene Testing

Modern food production relies upon high standards of hygiene at all stages. In processing a key aspect of hygiene is the cleanliness of equipment following terminal and breaktime cleaning procedures.

Unfortunately, the cleaning process can leave an area or a piece of equipment looking visibly clean but bacterially contaminated. The only way to ascertain the bacteriological effectiveness of cleaning is to undertake tests.

Several options are available but swab testing has stood the test of time and is the preferred option of many in the food industry. Swab testing has the benefit that it gives a good indication of the range of bacteria present and, should needs require, any bacteria present can be selected for further tests.

It is important to appreciate that all hygiene testing is a process to identify those areas or pieces of equipment that have been inadequately cleaned. That is, it is a management tool and not a scientific exercise!

Be careful when taking hygiene swabs that your approach is random. If you always test the same areas, staff will quickly appreciate this and focus their cleaning efforts on the areas you test! The results are good, but the status of the areas that were not tested is bad

Scope of testing

Hygiene testing can be used for:

• Give an overall indication of the degree of cleanliness.
• Give an indication if faecal contamination is present by testing for faecal indicators such as enterobacteriaceae.
• Give an indication of contamination from the operators (Staphylococcus aureus).
• Detect the presence (or confirm the absence) of specific bacteria such as salmonella or listeria.

Provision of test kit

Northern Hygiene Laboratories Ltd is able to provide you with all you need to do your regular hygiene tests including swabs, instructions and a submission form.

If enumeration and detection methods are required for the same area, seperate swabs will need to be used for enumeration and each detection method.

Stool Testing

Some high care food companies want to be sure that their staff are not carrying enteric foodborne pathogens.

This can be done by screening stool samples for bacteria such as salmonella and shigella.

We provide the test kit, you collect the sample and post it to us. We than test the sample and send you the result. (not part of UKAS Accredition)