Mechanically separated meat and meat structure

The provision of meat for retail involves removal of prime cuts, such as chicken breast fillets for example, leaving residual meat or flesh on the carcass. Like many industries, the meat industry has become more mechanised in its production, often using machines to butcher meat instead of manual labour. These machines, or the manual workers involved, are required to cut the meat away from the bone to avoid getting bone splinters in the product. This aspect, together with the large volumes involved in meat production, means that there is a considerable amount of good quality muscle meat remaining on carcasses. This valuable resource needs to be carefully removed so that it can be used in meat products to make the most of the animal. Carrying this out is an efficient use of an expensively produced product and helps to keep the cost of meat to the consumer down.

The residual meat remaining on the carcass can be removed using a machine which does not use a cutting action but more of a squeezing or rubbing action. There are different types of machines available from different manufacturers to do this, but they all work on the principle that the flesh is removed from the bones under some pressure, often using a sieve or mesh at some point. Contrary to some opinion, water is not used in the process. The level of pressure used to remove the residual meat can be adjusted to give different yields, and the process often uses two stages: the first stage being the removal of the meat from the bones, and the second stage being a desinewing step that removes sinews from the muscle portion. The resultant product using high pressure is what used to be considered typical MSM and generally has a soft liquid consistency with the appearance of a smooth paste. Legislation concerning MSM is in force under the Hygiene and Transmissible Spongiform Encephalopathies (TSE) regulations but there are also concerns around authenticity that the consumer should be aware that their product contains MSM.

Definition of MSM and the issue

Originally the definition of MSM was a product of mechanical separation of flesh which ran like a purée. The definition of MSM was later altered to one taking account of muscle structure. Regulation (EC) No 853/2004 defines MSM as: “the product obtained by removing meat from flesh-bearing bones after boning or from poultry carcasses, using mechanical means resulting in the loss or modification of muscle fibre structure.” MSM cannot count towards the meat content of products for the purposes of QUID requirements in EU Food Labelling legislation. It is also subject to rigorous handling procedures under the Hygiene and TSE regulations.

Regulation (EC) No 853/2004 also sets down different rules for MSM produced by techniques that do not alter the structure of the bones and those that do. It also takes account of whether the product has a calcium content that is not significantly higher than that of minced meat, for which a limit is set down in Regulation (EC) No 2074/2005.

Modern equipment for mechanical separation allows the operator to use much lower pressures to produce meat pieces from the carcass which are very similar to those removed by a blade or hand. This product is higher in perceived quality than the high pressure MSM in that it consists mostly of intact muscle fibre structure. However, if classified as MSM some consider it has a lower value than if it fell into the meat preparation category.

Regulation (EC) 853/2004 provides a definition for meat preparations as follows: “‘Meat preparations’ means fresh meat, including meat that has been reduced to fragments, which has had foodstuffs, seasonings or additives added to it or which has undergone processes insufficient to modify the internal muscle fibre structure of the meat and thus to eliminate the characteristics of fresh meat.” Therefore, according to the regulation, muscle fibre structure is highly relevant in differentiating between MSM and meat preparations.

There are two aspects to answering the question: ‘Why does it matter?’ The first is that flesh removed from the carcass by low pressure machine conditions is meat-like in appearance and composition, and different from the high pressure product. It therefore should have a higher value and be distinguishable from the high pressure material. The second aspect is that although high pressure MSM has a functional and nutritional value for the consumer and is safe to eat, it is considered that the consumer should be informed that it is present in the product. For efficiency and waste reduction reasons, all useable parts of an animal should be recovered and the benefits and production methods, safety of the product and reasons for using the machine recovery system need to be explained. This message is not being put across strongly enough to the consumer, so that the result is that MSM is perceived as not acceptable by some.

As detailed above, in the current EU definition of MSM the regulations refer to loss or modification of muscle fibre structure as being a main differentiator between MSM and meat. However, the real picture is more complex than this.

Meat structure

Meat is thought by many to be mainly the muscle parts of the animal, with some fat and connective tissue accepted as part of meat. The structure of intact muscle (meat) is highly organised (Figure 1) consisting of many muscle fibres or cells within the muscle. Like a Russian doll, there are several muscle filaments within each muscle fibre (Figure 2) and these in turn are composed of several fine interlocking fibrils of protein (Figure 3). The muscle fibres also have many nuclei within each cell, located at the edges of the fibres under the fibre membrane. Fine connective tissue and also thicker connective tissue is present between the fibres or fibre blocks, and there will also be blood vessels, fatty tissue and other structural elements present. Bone or hyaline cartilage should not be present in meat as these would be hard and unacceptable, although they are of course present in the carcass.

Processing of meat, such as mincing, freezing, salting and curing, all have an effect on the muscle fibre structure, and a meat preparation made using these processes is usually acceptable to the consumer as a form of meat. Research publications have shown that typical brining solutions, such as those used to prepare ham, affect the structure of the muscle fibre¹. Mincing and freezing also cause loss or modification of the muscle fibre structure (Figure 4).

Current position

Following the change in legislation defining MSM in 2006, Leatherhead Food Research carried out research projects for the Food Standards Agency and Defra on samples from machine separation and hand deboning to see whether examination using a light microscope could distinguish the low pressure material from the higher pressure MSM and from the hand deboned meat. Products from chicken, turkey and pork after separation and desinewing were examined and compared with hand deboned and minced meat2. This research was funded with the aim of developing a method for supporting enforcement of the legislation on MSM.

Results showed that the extent of damage to the muscle fibre structure in both the hand deboned minced meat and the low pressure MSM were similar to each other, but very different to the high pressure MSM (Figure 5). Therefore, the quality of the two types of sample (hand deboned meat preparation and low pressure MSM) was similar in terms of muscle fibre structure.

Following this research and on evidence from the literature, the UK position until 2012 was that the low pressure MSM (often called desinewed meat (DSM) or 3mm meat) could be considered as a meat preparation rather than MSM, thus suggesting a higher value in the food supply chain. However, in 2012, in an effort to try to standardise the situation regarding the definition of MSM within the EU, the situation changed due to a stipulation by the European Commission that such residual flesh removed by ‘mechanical separation’ from the carcass was to be declared as MSM. The production of MSM from ruminant animals is banned, so no low pressure material could be produced from the carcasses of lamb or beef.

The EFSA (European Food Safety Authority) produced a report³ summarising the published research on MSM and DSM, concluding that the microscopy method was useful to categorise the two, but was not quantitative and that the only analytical method which showed any form of trend to distinguish MSM and hand deboned meat might be a measure of the calcium content.

The MACSYS project

One of the discussion points in the MSM/DSM debate was whether the extent of damage to the muscle fibre structure could be quantified as the method using microscopy was a subjective one. If it could be quantified then there might be a way to measure or grade the quality of a meat preparation. To try to deliver this aim, a project termed MACSYS was proposed and financed. MACSYS started on 1st January 2014, and is a two year project involving nine partners, including research institutions and companies from six EU countries and Iceland.

Leatherhead Food Research is one of the research partners. The project is financed by the European Union’s Seventh Framework Programme and has received €1,247,404 in funding. It involves research into the development of a software image analysis package based on different microscopy approaches to determine muscle fibre damage. In addition, the MACSYS project is developing a fast track method which can automatically estimate the muscle integrity directly in the process line, thus increasing the quality control. Research from the project will be published early in 2016, and more information can be obtained from the website: www.macsysproject.eu.

The current discussion involves whether low pressure MSM should be considered as MSM or a meat preparation, whether it can be distinguished from hand deboned processed meat, and whether it should be allowed to count towards the meat content. The discussion is an important one as it covers issues of economic concern, the need for accurate labelling of food products to enable consumer choice and the production of a level trade situation and smooth functioning of the EU internal market.

Although the microscopy method used at Leatherhead is not quantitative, it can evaluate the level of damage to the muscle fibre structure in samples. This can be used as guidance for meat producers in evaluating the quality of the MSM or meat preparation. Leatherhead received UKAS accreditation in this method in 2014, and it is available as a testing service.

References

1. Lewis, DF, Groves, KHM, and Holgate, JH, (1986). Action of polyphosphates on meat products. Food Microstruct. 5. 53.
2. Groves, K (2011). Q01101-Evaluation of a Simple Microscopy Protocol for Identifying Mechanically Separated Meat (MSM) in Pork, Chicken and Turkey. Defra report. Leatherhead Food Research, http://randd.defra.gov.uk/Default.aspx?Menu=Menu&Module=More&Location=None&Completed=0&ProjectID=18019.
3. EFSA (2013). Scientific Opinion on the Public Health Risks Related to Mechanically Separated Meat (MSM) Derived from Poultry and Swine. EFSA Journal, 11(3):3137, http://www.efsa.europa.eu/en/efsajournal/pub/3137.htm.

About the author

Kathy Groves graduated in Biochemistry at the University of London and joined Leatherhead Food Research as a food microscopist. She now manages the microscopy section within Food Innovation. She has over 35 years’ experience in the food microscopy field, covering research into a wide range of food products including protein functionality, meat product quality, emulsions and confectionery products, as well as product contamination. She specialises in methods to characterise the structure of foods, especially confectionery products. She has recently worked with the Food Standards Agency and Defra on methods to detect mechanically separated meat and has presented on nanotechnology to the Government. Kathy is a Fellow of the Royal Microscopical Society and a member of the Institute of Food Science & Technology. She has also been recently appointed as Visiting Professor at the University of Chester.