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Good Manufacturing Practices Will Prevent Meat Species Contamination

16 June 2014

Food authenticity failures and food fraud can be driven by pressures on food production and the current climate of financial constraint

The horse meat incident which emerged in early 2013 impacted on confidence in the UK food supply chain and showed that the presence of undeclared species in meat products is of concern to consumers, including those consumers, who choose to avoid certain species from their diets on the basis of faith.

However a study carried out by the Laboratory of the Government Chemist for the Food Standards Agency and the Department of Environment, Food and Rural Affairs found that when raw minced beef is produced according to good manufacturing practices, either a deep chemical clean or a high pressure water wash between species is effective in preventing the carry-over of contaminant m3eats in to the final product.

The incident with the presence of horse and pork meat in processed beef products in 2013 raised a number of questions including whether carry-over, i.e. adventitious contamination of meat species occurs during industrial production of meat products prepared according to good manufacturing practice (GMP).

A review of scientific literature showed that information on the carry-over of meat species during commercial processing was not available.

As a consequence, the Food Standards Agency (FSA) and the Department for Environment, Food and Rural Affairs (Defra) commissioned a research project to assess whether carry-over of meat species occurs during the industrial production of minced meat according to GMP in the UK and, if it does, at what concentrations it occurs.

The project plan was devised by LGC with input from statisticians and was widely consulted on with industry groups and Defra’s Authenticity Methods Working Group (AMWG) (Expert advisory group).

Although it was acknowledged that there are many points during the meat processing process that could give rise to the carry-over of meat species, it was agreed by experts that the mincing stage was the step that had the greatest potential risk for gross contamination.

The project therefore focussed on the mincing process.

Two commercial quantitative real time PCR kits were selected for use in this project; one for the analysis of carry-over of raw pork in raw beef meat samples and the other for the analysis of swab samples to test for the presence of pork.

Before any samples were processed, the analytical procedures were validated at LGC using gravimetrically prepared, on a weight: weight basis, quality control materials.

A reporting limit of 0.1 per cent raw pork in raw beef was established and further work indicated that a LOD of 0.03 per cent raw pork meat in raw beef was achievable.

It was also established that there was no statistical difference between the results reported as a percentage of pork DNA and the actual percentage pork present determined by mass, but a consistent positive bias was observed. Evaluation of the results obtained for the 0.1 per cent raw pork in raw beef quality control standard estimated a reported pork content of 0.04 to 0.27 per cent; this variation is in line with expectations when working at the reporting limit of a method.

The results for this project are reported on a quantitative weight: weight basis and represent the ‘best case scenario’ in that the standards and samples were made from the same authentic lean meats.

The project was conducted in two phases; phase 1 was carried out in a commercial pilot plant under controlled conditions and phase 2 trials were carried out in three working UK commercial plants.

Both phases focussed on raw pork carry-over into raw beef mince.

Input meat for phase 1 was sourced from single species abattoirs after an audit of the process by LGC staff. Input meat for phase 2 was provided by the plants from their intake meat used for production.

All mincing and cleaning operations were conducted by plant staff and all meat samples were taken by LGC staff. A total of 1032 beef samples and 390 swab samples were analysed.

The results from phase 1 showed that both deep chemical cleaning and cleaning with high pressure water of industrial mincing equipment and conveyor belts in line with GMP were effective in preventing carry-over of pork meat into beef (down to 0.1 per cent raw pork in raw beef on a weight for weight (w/w) basis).

These results were confirmed in the phase 2 when the work was replicated in commercial plants using their input meats and processes.

When no cleaning was carried out between species processing, both the phase 1 and phase 2 studies showed that significant carry-over of pork meat into beef meat does occur.

The level of carry-over in each was, however, different. In the pilot plant study carry-over of pork into beef was most significant in the first 0.75 kg of meat where the concentrations ranged from 99 per cent to 54 per cent pork.

The estimated pork carry-over in the 100 kg of beef processed in the pilot plant trial was 653 g (0.65 per cent), whilst the estimated pork carry-over for experiments carried out in a commercial plant was 11.2 kg in 200 kg (5.6 per cent).

The difference in the estimated pork carry-over between pilot plant and commercial plant studies is thought to be due primarily to the differences in the mincing equipment used, e.g. size, age, complexity, potential traps points etc….

This indicates that the amount of carry-over will vary from plant to plant based on the equipment and processes used. This report provides clear evidence that detectable levels of carry-over does occur when no cleaning is undertaken between species which needs to be considered by manufacturers when presenting information to consumers about the composition of meat products so the contents are accurately described.

To check the effectiveness of the cleaning regimes used in commercial meat plants (deep chemical and water wash), three types of swabs were taken; adenosine triphosphate (ATP)(ATP is present in all organic material and a positive reading is an indication of the presence of contamination, for example food residue, allergens and/or bacteria), protein and DNA swabs.

Following a deep chemical clean, all three swabs gave equivalent negative results demonstrating that any one of the three swab methods may be used to check the effectiveness of cleaning. However, although the majority of swabs taken after the water wash also gave negative results, there were some notable differences:
• One positive protein swab result was obtained (negative after re-cleaning)
• Several very high ATP results were obtained (reduced after re-cleaning).

The results indicate that from a practical perspective, of the two cleaning methods used, the deep chemical clean is the most effective cleaning method as all swabs taken by all three swabbing methods gave negative results in both Phase 1 and 2. In addition, no carry-over was observed in any of the beef samples taken after a deep chemical clean.

The water wash method did give rise to one protein failure and a number of ATP failures (in both phase 1 & 2) demonstrating that greater care is required to ensure cleaning is effective in removing all traces of organic matter. However, no carry-over was observed in any of the beef samples taken after a water wash demonstrating that it is an effective cleaning method, with regards to preventing carry-over, for equipment which is readily accessible and can be easily dismantled.

Unless it is important to monitor the effectiveness of cleaning with respect to proteins, e.g. in plants producing allergen-free food or with respect to individual meat species, e.g. Kosher / Halal plants, then the protein and DNA swabs offer no further advantage to the ATP and cost more to undertake.

Thus, of the three types of swabs taken, ATP appears to be an appropriate cost-effective way to monitor the cleanliness of equipment with regards to generic traces of residue provided each plant undertakes the validation required to establish its own control limits.

The project has fulfilled its objectives and generated data that previously did not exist in the scientific literature.

It has been established that when raw minced beef is produced according to GMP, either a deep chemical clean or a high pressure water wash between species is effective in preventing the carry-over of raw pork into raw beef with an associated limit of detection (LOD) of less than 0.1 per cent on a w/w basis. The project has also shown that when no cleaning is performed between species, carry-over does occur which needs to be considered by manufacturers when presenting information to consumers about the composition of meat products so the contents are accurately described.

Stakeholders now have the evidence to differentiate between adventitious contamination of raw pork mince in raw beef mince and deliberate fraud.

There should not be an expectation of adventitious contamination and the presence of low concentrations of undeclared species in relevant meat products, as this project has shown that it is possible to clean to <0.1 per cent pork w/w using GMP employed in UK meat processing plants.

The outcomes of this project are based on the determination of raw pork in raw beef only.
Whilst it would not be unreasonable to assume the outcomes would be similar for other species of meat, the work needed to confirm this assumption was not within the scope of this project.

Further Reading

You can view the full report by clicking here.

June 2014


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