MDM – Not all are created equal!
By Eben van Tonder
16 April 2018
Introduction
Last Saturday I turned 50. I did three things that I insanely enjoy. One was to spend time with a meat and business legend. Over the years I have researched and got to know many such men. Those who are still alive, I got to know personally. Those who passed away, I studied their lives. Jacobus Combrink who created arguably the most successful butchery in South Africa in the 1800s; David de Villiers Graaff, his protege and the man who took Combrink & Co. and turned it into the Imperial Cold Storage and Supply Company Ltd. (ICS) which in turn merged into the food conglomerate Tiger Brands with the Combrink & Co part of the operation being assimilated into the Enterprise/ Renown merger; JW Moore who set up the Eskort curing operation under his Farmers Cooperative Bacon Curing Company in Estcourt, Natal. Further afield there is the three Harris’s. Nick Harris, whom I have the privilege to know, was key in the creation of the New Zealand curing operation, Hellers. Together with his brother, Bryan, they currently own an abattoir, deboning and processing plant in Cheviot where they grow up and where Nick owns large farmland. From the previous century, the brothers George and Thomas Harris from Calne in Wiltshire who created C & T Harris, arguably the most successful bacon operation in British history. From Australia, Wright Harris and his Castlemaine Bacon Company who fought in the second Anglo-Boer war in South Africa. Interestingly enough, none of the Harris’s from New Zealand, Australia or England are related. From the USA there is the legendary Philip Armour and his Armour Packing Plant in Chicago who was, according to my research, closely linked with the direct addition of nitrites in curing brines. His company is one of the reasons why anti-trust laws exist in the USA. For my 50th birthday, I was on the farm of Etienne Lotter.
Etienne stands shoulder to shoulder with any one of these formidable men. It fascinates me that all these men share an unwavering focus, the ability to make quick and good decisions, resolve of steel, passion, commitment, and an obsession to invest in people. A story is told of Phil Armour that he showed his packing plant to visitors one Sunday. Ford got his idea about assembly lines from Phil and it was indeed something to behold. A newspaper reporter tells the story that they were walking back from the factory and could see the church where many of the men who worked for him attended adult education after church. He reportedly pointed to his packing plant and said, “there we make bacon” and then to the church and said, “and there we make men!” He liberally invested in people and he himself claimed that he never fired someone. That is not to say that it was easy to work for him as is or was true of all these men.
The second thing I did which I insanely love was to hike up the Magaliesburg on Etienne’s farm, Eswitch Stud Farm. There was no clear footpath up and it made for an adventure through the thick grass, trees, and ferns.
The 3rd thing was talking meat curing with Etienne the entire Saturday and Sunday morning! The experience was volcanic with its seismic aftershocks still reverberating through my psyche! I’ve been in the meat industry no for 14 years. Till my day with Etienne, I thought of MDM (Mechanically Deboned Meat) as something like flour or sugar, a commodity of uniform characteristics and quality. Was I wrong! It turns out that as is the case with all ingredient, functionality follows processing techniques. Inspired by Etienne’s passion for MDM, I started to investigate What a world started opening up! I share some of my initial discoveries.
Definition
“Mechanically deboned meat (MDM), mechanically recovered meat (MRM) or mechanically separated meat (MSM) are synonyms used to mark the material, obtained by application of mechanical force (pressure and/ or shear) to animal bones (sheep, goat, pork, beef) or poultry carcasses (chicken, duck, turkey) from which the bulk of meat has been manually removed” (Hui, 2012)
There are a number of different methods to achieve this, but most of them result in cell breakage, protein denaturation, generally an increase in lipids and haeme groups and poorer mechanical properties. (Hui, 2012)
MDM is mainly used in producing emulsion-type products such as Vienna’s, Russians, and Polony (in South Africa). “Meat recovered from bones or carcass parts by mechanical procedures is generally considered to be of poor nutritional and microbiological quality” (Hui, 2012) In many parts of the world, strict legislation governs the use of these products. When compared to the rest of the world, South Africa lags behind in this regard. There are certain producers who choose to only use muscle meat in the production of its emulsion sausages, loaves, and hams, and the consumer is entirely left to study ingredients declarations to determine if MDM is present or not. There are also a number of different qualities of MDM and it is by no means correct to claim that all MDM are of poor microbiological quality and share the same low nutritional characteristics. The different production methods of MDM can broadly be separated into hard and soft MDM.
Hard MDM
Hard MDM is made from pork or beef where it will be hard to clear the bones from all the small meat bits. When the valuable pieces of chicken and turkey (wings, breasts, and legs) are removed, hard MDM is made from the carcass that is left. In this method, the bones or carcass is placed in some kind of a pressure chamber with small holes in it and the bones or carcasses where are subjected to high pressure which removes the skin, meat bits, connective tissue, etc. still stock to the bones. These pass through the small holes of the barrel sieve (around 0.5 – 0.8mm in diameter). The basic principle remains the same across many different machines namely that high pressure is used to clean the bones. (Feiner, 2006)
Hard MDM should not contain bone bits larger than the hole size of the sieve, but in reality, on account of the enormous pressure used to remove the fragments from the bones, they often do. The consequences of the presence of bone pieces in the MDM elevates the calcium and phosphorus content in hards MDM quite high. These, in turn, interferes with the functionality of phosphates in emulsion sausages. (Feiner, 2006)
The micro status of hard MDM is of great importance. The reason for the high micro in this MDM is the large surface area of the meat. The levels should not be higher than normal minced meat. As always, processing conditions play the key role here and low micro levels are never guaranteed. (Feiner, 2006)
Another problematic feature of hard MDM is the presence of bone marrow, particularly in chicken MDM. This speeds up the oxidation of fat since bone marrow contains a fair amount of metals such as iron, magnesium, and copper “which acts in a pro-oxidative manner.” (Feiner, 2006)
The fat content of hard MDM is inconsistent. Protein, fat and bacterial levels should be part of MDM specifications. The shelf life of pork and chicken MDM is much shorter than beef MDM in both chilled and frozen state. The reason is the fatty acids in pork and chicken have high levels of unsaturated fatty acids in the fat fractions when compared with beef. “Rancidity develops quickly within such material.” (Feiner, 2006)
MDM has a pasty texture. Due to the meat recovery method, there is a high proportion of “pulverised muscle fiber residue.” There is also a large proportion of “partly destructured muscle fibers.” We call such change in muscle fiber ‘‘destructuration” (Sifre and others 2009)” (Feiner, 2006)
Soft MDM
Soft MDM, on the other hand, is produced from meat trimmings, high in connective tissues. The process avoids the enormous pressure of the hard MDM methods by the action of a roller on the meat. In this system, the material is put through a machine that separates the meat from connective tissues, cartridge, etc. based on the different hardness of these components. The process is much more productive in terms of time and input required when compared to the hard MDM methods. In many instances, a “Baader” machine is used or something similar. (Feiner, 2006)
A very typical production method is as follows.
- Grind minced meat through 13 – 20mm mincer plate;
- Feed through Baader machine
- The Baader machine has small holes in a rotating drum and the meat passes under the drum so that the drum presses ON the meat. The soft lean meat, due to its texture, passes through the holes in the rotating drum and is collected there and fed out on the side of the machine;
- The harder connective tissue, bone fragments, etc. are ejected at the front of the machine, having been unable to be pass to the inside of the drum where only soft lean meat is collected. (Feiner, 2006)
Both the collected connective tissues, sinews, etc and the soft MDM from inside the drum has enormous functional applications and products are made from both.
Comparing hard MDM and soft MDM, the following functional differences emerge:
| Soft MDM | Hard MDM | |
| Protein Content: 15% – 17% | Protein Content: 12% to 15% | |
| Of this, 70% to 80% is equal to protein found in muscle meat. | Of this, 60% to 70% is equal to the protein found in muscle meat. | |
| Consequently: | Consequently: | |
| – Much improved WBC (Water Binding Capacity); | – Reduced ability to immobilise water | |
| – Much improved ability to emulsify fat | – Reduced ability to immobilise emulsify fat | |
| 70% to 80% WBC and emulsifying characteristics of lean muscle meat | ||
| All protein in soft MDM still functional | Reason is: denaturing of proteins and cell breakage during processing. | |
| Fine and mushy consistency | ||
| Consequently: | ||
| – Do not support firmness in final product | ||
| pH: between 6.2 and 6.4 | ||
| Consequently: | ||
| – poor colour developmenty | ||
| – MDM only products exhibit a darker colour. |
Legislation
Examples of legislation in place in many parts of the world related to MDM are the following:
Bones to be used in the production of Hard MDM must be stored at between 0 and 2 deg C no longer than 24 hours or be frozen for a maximum of 8 days before it is processed. If it is frozen, this must take place immediately after production. The chilled bones must be utilized within 24 hours.
Besides these, fat percentages, minimum requirements on nutritional value, and percentage connective tissue are set in many countries.
Functional Characteristics
Despite the fact that many different MDM producers achieve these values, there exists an enormous range of varying functional characteristics of MDM, produced by different manufacturers, on account of different process and machines employed in its production.
Lets first evaluate meat that was recovered through deboning with meat processed with an MDM machine. Froning (1970) for example compared hard deboned white and dark chicken meat with chicken backs and necks and turkey frames processed with a Paoli machine and chicken backs processed with a Beehive deboner for emulsification properties. (McMillan, 1980)
He found that MDM was most stable in a bowl cutter to temperatures of 7.2 to 12.8 deg C. Above 12.8 deg C, the tensile strengths of finished emulsions decreased and the amounts of fat and gel-water released during processing increased. By comparison, the hand boned broiler meat was stable at all chopping temperatures. (McMillan, 1980)
He further found that MDM had less protein matrix available for emulsion than hand-deboned meat, “due to greater collagen dispersion and possible loss of protein solubility caused by deboner protein denaturation.” (McMillan, 1980)
The tests may have been conducted in the 1970s and 1980s, but the principals are equally valid. Froning et al. (1971) used 15% turkey MDM in red meat frankfurters to study its stability and acceptability. The MDM was produced with a Paoli deboning machine and the results indicated a higher capacity to emulsify oil per 2.5g sample than pork trimmings, but a reduced capacity than boneless cow meat. (McMillan, 1980)
Turkey MDM had a reduced WHC compared to red meat sources. Gel-water loss was greater in frankfurters made with 15 percent turkey MDM. Their research alluded me to another very important consideration in the functionality of MDM. In SA, all MDM is sold frozen, but in other countries, MDM is customarily produced, sold and used unfrozen. Froning et al. found that frankfurters which fresh MDTM had less cook
than franks containing MDTM which was stored frozen for seven days prior to use. (McMillan, 1980)
In terms of taste, no major differences were found between control frankfurters, frankfurters containing previously frozen turkey MDM and fresh MDM in terms of taste and colour. The superiority of pure meat over MDM was confirmed by Schnell et al (1973). They compared poultry MDM with hand boned carcass meat. The texture frankfurters produced with hand-deboned meat was firmer than those produced with MDM. (McMillan, 1980)
Another interesting study, confirm the differences between different MDM producers was done by Baker et al. (1974). They compared poultry MDM from three machines to measure the effect of chopping time on taste panel evaluation and frankfurter stability. “Chopping time had little effect on results of these tests, but source of the MDPM caused differences in frankfurter yield, stability during cooking, emulsion viscosity, and taste panel scores of texture and juiciness. More dense poultry MDM and smaller, more evenly distributed fat globules contributed to the stability of frankfurters with two of the poultry MDM sources as compared to the third MDPM source (Angel et al., 1974). (McMillan, 1980)
Some researchers have reported that they were able to “manage” negative characteristics in certain MDM typed through various techniques such as controlling and altering the pH, but if this can be duplicated in a factory environment if questionable.
Foodnavigator reported in 2018 on a project in the EU seeking to test MDM in terms of the structural integrity as a key indicator for its quality. The software reportedly use image processing algorithms to quantify degrees of degradation in meat. The aim is to test cheap imports into the EU which claims comparability with high quality EU MDM.
In the EU, certain producers such as Polskamp Meat Industrie in Holland is able to produce MDM of exact specifications. Processors can choose fat content of ±11%, ±12%, ±14% and ±16% and protein content of between ±15% to ±18% The colour of their chicken MDM is consistent being the typical colour of fresh chicken meat of pink-red. This sets them apart from many producers who is unable to certify such exact parameters, again confirming our thesis that not all MDM are created equal!
Polskamp is a good example of using technology to overcome the inherent problems in hard MDM. They pioneered low pressure technology to remove meat from bones, thereby avoiding the negative aspects associated with high pressure meat separation.
They claim that their 3 millimeter meat is “produced using special machines that can separate meat from the bone. Contrary to mechanically separated meat, 3 millimeter meat is produced using low-pressure technology that better preserves the structure of the chicken meat. 3 Millimeter meat is also characterised by its lower calcium content and lighter colour. Polskamp Meat Industrie offers its buyers several types of 3 millimeter meat, e.g. a white product and a rose-coloured product.” (polskamp.com)
Conclusion
These and more recent studies indicate the need for the processor to conduct a thorough evaluation of its MDM source. At the end of the day, all these studies point to the fact that the different MDM’s on the market, produced by various manufacturers, using a range of different source material’s are not all created equal.
By choosing the right MDM source, it may be possible to omit binding and water absorption material such as the different soya products or starches. The effect of freezing and freezing time on MDM is another key aspect to be evaluated and along with aspects such as fat %, connective tissue%, and water content must command our careful attention.
Finally, careful attention should be given to the different methods to extend the shelf life of MDM by reducing lipid peroxidation and of microbial growth.
Even if pure meat products is our objective, the lessons found in the production of MDM and the subtle techniques of optimizing yield, profitability while achieving exceptional product quality will benefit us tremendously if we master it!
Further Reading
The nutritional and physical characteristics of mechanically proc
Hui, Y. H. (Editor) 2012. Handbook of Meat and Meat Processing. CRC Press.
Hiking photos
It is not every day that one turns 50. Here are the rest of the photos from my hike up the Magaliesberg on 13 April 2019.
References:
Feiner, G. 2006. Meat Products Handbook: Practical Science and Technology. Woodhead Publishing.
Hui, Y. H. (Ed.) 2012. Handbook of Meat and Meat Processing. Chapter: Mechanical Deboning. CRC Press; Taylor & Francis Inc.
McMillan, K. W.. 1980. The nutritional and physical characteristics of mechanically processed beef and pork product. Iowa State University. Retrospective Theses and Dissertations. 7342. https://lib.dr.iastate.edu/rtd/7342
https://polskamp.com/product/3-millimeter-meat/
Photo Credit:
Continental Franks: https://www.amazingfoodmadeeasy.com/define/charcuterie/what-is/frankfurters
All other photos by Eben