#Compoposition

[ebenvt]

Poultry MDM: Notes on Composition and Functionality by Eben van Tonder 5 July 2020

Background

The mechanical deboning of meat has its origins from the late 1940s in Japan when it was applied to the bones of filleted fish.  In the late 1950s, the mechanical recovery of poultry meat from necks, backs and other bones with attached flesh started.  (EFSA, 2013) A newspaper report from the Ithaca Journal, Wed, 30 Dec 1964 is the earliest reference I can find on Mechanically Deboned Meat (MDM) in America. It reports on research done at Cornell State College of Agriculture in an article entitled, “New Egg Package, Chicken Products Are Among 1964 Research Results.” It reports that “mechanically deboned chicken meat was put to use for the first time, and improvements were in new types of harvesting machines.”

It claims that MDM based products would be available from 1964. “Late in 1964 Cornwell researchers began preparing experimental chicken products from this meat, which resembles finely ground hamburger.” It said that the new chunky type chicken bologna, was introduced in three forms: Chicken Chunk Roll, which is half chunk meat, and Chicken Chunkalona, which is 25 per cent chunks and 75 per cent emulsion.”

By 1969, several American universities were working on these products, including the University of Wisconsin.

The Oshkosh Northwestern, Thu, 21 Aug 1969

By the early 19870s, the removal of beef and pork from irregularly shaped bones was introduced. Originally, the aim of MDM was to reduce the rate of repetitive strain injury (RSI) of workers caused by short cyclic boning work in cutting rooms of meat operations. A press was developed to accommodate this.  The success of the approach resulted in a rapid acceptance of the principles and an incorporation of the technology across Europe and the USA.

As is the case with meat processing technology in general, despite recent developments of the process, the basic approach is still the same as the first machines that was built.  Initially primitive presses derived from other types of industries were used to separate the meat from the bones, using pressures of up to 200 bar. A fine textured meat paste was the end-product, suitable for use in cooked sausages. Gradual technological improvements and pre-selection of the different types of flesh bearing bones pressed at much lower pressure (up to 20 bar) produced a coarse texture of higher quality meat that could no longer be distinguished from traditional minced meat (so called 3 mm or Baader meat).

Today, a wide variety of different products are available on the market from many different suppliers of every imaginable animal protein source.  Legislation differs widely between different countries on the definition of MDM.  Different countries name and classify it differently and the astute entrepreneur will find opportunities in studying every aspect of this fascinating industry closely, especially in the maize of ever evolving legislation related to it around the world. As one country restricts its use on one front, other countries will be able to buy a particular grade or type at better rates and this will in turn open up opportunities in the buying-country’s market for new ways to use raw material which becomes available for it due to a drop in the price. My own foray into this world took place during a year when Woody’s gave me the opportunity to spend almost a year working with companies in England.  The project I worked on was high injection pork.  During this time there were changes to legislation related to ground pork.   I witnessed UK prices plummet on a commodity which, in retrospect, we should have pounced on, but I knew far too little about the sausage market to exploit the opportunity.  In retrospect, I knew far too little about anything related to meat, but that is a story for a different time and many of my friends who gave me a chance to work with them and to learn will smile at this!  My business partner in the company we founded and where neither of us are involved in any longer will certainly have a good chuckle!

Between 10 May and 8 June 2012, at the Tulip plant in Bristol, England, we extended ground pork with 60% brine which was designed by Andreas Østergaard.  Brine was tumbled into the meat, heat set, chilled, frozen and sliced. Evaluating the texture of the final product now, almost 8 years later to the day, I realise that we should have used it to create a fine emulsion for a sausage or loaves. Looking at the result of the 60% extension below, we could easily have targeted 100% or even higher.  What could we have landed the raw material at in SA if we created a fine emulsion base, extended 100% or 150% with rind emulsion added and used it as the basis for a number of fine emulsion based products at our factory in Kraaifontein, Cape Town?  Evaluating what we did in Bristol, the heat setting, even in our course loaf-like product, was inadequate for proper gelation, which is clearly seen in the photos below.  

All the photos related to these trails can be seen at: https://photos.app.goo.gl/LX6uZheqeBeUa1mWA

The lesson for me is that in order to exploit these realities, one must grasp the functional value of the raw material, which in our consideration here is MDM, but must most certainly include other similar products not necessarily classified as MDM, MRM or MSM such as ground meat or something similar.  This will lead to an appreciation of the differences between various grades of MDM and related products, which will allow processors to develop new products and increase its bottom line / reduce selling prices of others as new MDM products become available and countries adjust its legislation to regulate its use.  It all begins by understanding the basic principles at work in this immense and fascinating world. We begin by looking at the basics of poultry MDM.

MDM Stability

Poultry MDM has been shown to have more constant composition compared with pork, veal and beef MDM. Considerable variations in fat and protein content occur in poultry MDM. The amount of back, wing, neck, rack, skin (or no skin) or the ratio of starting material used and type of deboning machine and settings play a major part in final product composition.  Deboner head pressure was increased x 3 to increase the yield from 45 to 82%; fat content significantly reduced and moisture content increased. This is an interesting observation. (Hudson, 1994)

Rancidity problems stem from the method of production. Air with increased iron because of bone marrow are the major reasons. Additional fat stems from bone marrow and skin. Phospholipid fraction, as a percentage of total lipid content, is only at about 1 – 2% in poultry MRM.  Over 60% of this may be unsaturated, oleic, linoleic, arachidonic acid. These acids decrease in concentration during freezing or frozen storage of turkey meats or nuggets made from chicken MDM. This (the decrease in polyunsaturated fatty acids) may be explained by reports that chicken muscle homogenates to contain enzymes capable of oxidizing both linoleic and arachidonic acids and one was found to be stable during frozen storage, being 15-lipoxygenase. (Hudson, 1994)

Iron in MDM acts as a catalyst in lipid oxidation is well known, but -> is it haem or non heam iron that plays the dominant role in poultry?  Lee et al. say that haem protein, (50% of total iron) is the dominant catalyst for lipid oxidation in poultry MDM. Igene et al. claim that “warmed over flavour” of cooked chicken meat (whole muscle) is due to non-haem iron release during heating, which is the catalyst for oxidation.  Kanner et al. say that one reason why haem protein effects lipid oxidation only after heating was that catalase activity was inhibited and this allowed H2O2-activated mayoglobin to initiate peroxidation. Related to uncooked meat, these authors report an iron-redox cycle initiated peroxidation and the soluble fraction of turkey muscle contained reducing substances which stimulated the reaction. Free iron in white and red meats of chicken and turkey increases in concentration with storage time and is capable of catalyzing lipid oxidation. (Hudson, 1994)

Decker and Schanus used gel formation to separate an extract of chicken leg muscle into three protein fractions. One catalysed over 92% of the observed total linoleate oxidation. Iron-exchange chromatography of this active fraction revealed three proteins capable of oxidising linoleate. Haemoglobin was responsible for 30% of total oxidation while two components (according to Soret absorbance) were non-heam proteins and responsible for 60%.  (Hudson, 1994)

Much work in this area remains.

Modification of Poultry MDM

-> Texturing

The paste-like nature of poultry MDM limits its use. Early investigations focused on ways to “texturise” it. This can be done by adding plant protein or by various heat treatments. Sensory properties are not always what is desired.

One method of producing MDM products is to use a twin-screw extrusion cooker.  (Extrusion Cooking) has shown – treatment of poultry MDM alone gives unsatisfactory results.  The fat content of the material is too high. Satisfactory products similar to meat loaf or luncheon meat were achieved if, as binding or gelling agents, cereal flours, corn starch, egg white concentrate or soy protein isolate were combined with the MDM. This begs the question as to the gelling temperature of these products.

Alvarez et al. found that chicken extruded with 10 or 15% corn starch, lipid oxidation decreased as extrusion temperature rose from 71 to 115.5 deg C. They suggest that antioxidants were produced with increasing temperature. Hsieh et al. reported that a mixture of turkey MDM (40 parts) and corn flour (60 parts) increased in susceptibility to lipid oxidation above 110°C. The antioxidant BHA (butylated hydroxyanisole) was added to the raw materials before extrusion.

-> Haem Removal

Haem pigments in the product impacts on product stability and in poultry MDM it has a tendency to create a dark colour in the final products. Much effort is expended to remove these pigments and so extend the range of products in which the MDM may be used.

Froning and Johnson showed that centrifuging poultry MRM would remove haem pigments.  Washing procedures was first developed in Japan to remove haem proteins, enzymes and fats from fish during the production of the myofibrillar protein concentrate, surimi.  A lot of work has been done to extend the same procedure to washing MDM. However, there are several reasons why surimi technology might not be applied directly to poultry MRM, viz:

1. Surimi is prepared from whole muscle while poultry MDM is isolated from bones after most muscle tissue is removed. 2. Poultry MDM can have considerable quantities of connective tissue in the final product, e.g. histochemical investigations have shown the connective tissue: muscle ratio of chicken MRM to be 1 : 1.2. 3. Fish mince is frequently washed during preparation, but water washing is not an efficient means of removing haem pigments from MRM. 4. Lee suggested the size of perforations in the deboner drum of fish deboners ranges from 1 to 5 mm, with orifices of 3 to 4 mm giving the best quality and yield of surimi. Poultry deboners seem to have a pore size below 1 mm and thus the particle size of the products will differ. Since the term ‘surimi’ has long been associated with the product isolated from fish muscle, it is perhaps debatable as to whether the term should be applied to the material prepared from poultry MRM.

Other terms used are:

‘washed mechanically deboned chicken meat’ , ‘myofibrillar protein isolate’, (MPI), ‘isolate of myofibrillar protein, (IMP). The acronym IMP is problematic since it is widely accepted as an abbreviation for inosine monophosphate. Clearly some rationalization of nomenclature is required and perhaps a term such as ‘poultry myofibrillar protein extract’ would be more appropriate.

One of the earliest studies of poultry, turkey neck MDM, considered to be the darkest poultry MDM, was washed either three times in water or once in 0.04 M phosphate at various pH values, followed by two water washes. Then, the mixtures were pressed through cheesecloth to remove as much moisture as possible. The yield of paste from water-washed MRM was higher than that which had been treated with phosphate, but it had a darker colour. The researchers concluded that washing with 0.04 M phosphate at pH 8.0 provided the most efficient means of removing red pigment from turkey MRM. Froning and Niemann reported that extraction of chicken MRM with 0.1 M NaCI significantly reduced fat concentration and colour, and increased protein concentration. Others, using different washing techniques, particularly the use of bicarbonate as the washing medium, have found that either the protein content of the washed material was similar to that of the starting material, or was up to 7% lower.  However, all agreed that washing drastically reduced the fat level of the recovered material.

Washing with bicarbonate appears to be the most efficient way of removing pigment from poultry MDM, probably due to the fact that the pH value of the slurry makes the blood proteins more soluble, there may be other factors at work to influence the final colour of the washed product. For example, Trziszka et al. found that if, following bicarbonate extraction, water washing was carried out at pH 5.5, the product was lighter than at pH 6.0, while the variable amounts of connective tissue present in the washed residue can influence the appearance of the material, as shown by Kijowski et al., who found that removal of connective tissue by sieving increased both the darkness and redness of water-washed chicken MRM.

The yield after washing range was 13.5 to over 62% of the starting material.  Reasons for this variety may be the result of a number of factors such as source material for MRM, grinding of MRM before washing, nature of washing medium, washing time, adjustment of pH, number of washes, ratio of MDM to extractant and centrifugal force applied during separation of ‘meat’ and extractant.

Cryoprotectants, such as mixtures of sugars and/or phosphates, must be added for the washed material to retain its gelling and water-holding abilities during frozen storage. Washing improved the functional properties of the material – after cooking the washed MDM was more chewy, less cohesive and had increased stress values but the cooking losses from washed material were higher, probably due to the fact that ‘free’ water was absorbed during washing. The best indication of the success of the washing procedure is probably in practical terms measured by the performance of the myofibrillar complex in products.  There have been a few studies who looked at this. Frozen-thawed, bicarbonate washed turkey MDM at a level of 10% reduced the fat level of frankfurters, while increasing the expressible moisture content and resistance to shear compared with control frankfurters. Scanning electron microscopy did not reveal any obvious structural differences between controls and frankfurters containing 10% washed MDM. Hernandez et al. reported – the protein paste from washed turkey MDM could be incorporated into patties at levels up to 20% without adversely affecting sensory quality. Trziszka et al. reported that up to 50% of the ground chicken meat in hamburgers could be replaced by carbonate-washed turkey MRM without reducing the acceptability of the product. A sensory panel gave slightly lower flavour scores to hamburgers containing the protein extract, although whether this was due to the ‘soapy’ taste reported by Dawson et al. is not clear.

-> Improving Emulsification and Gelation

Although the protein complex isolated from washed MRM could be of use in altering textural properties of poultry products, further possibilities of effecting such changes exist. For instance, Smith and Brekke found that limited acid proteolysis improved the emulsifying capacity of actomyosin isolated from fowl MDM, as well as improving the quality of heat-set gels. Kurth used a model system to demonstrate the crosslinking of myosin and casein by a Ca-dependent acyltransfer reaction catalysed by transglutaminase (EC 2.3.2.13; R-glutaminyl peptide amine gamma-glutamyl transferase). Application of the technique to actomyosin prepared from turkey MDM showed that actin did not polymerize, but that the disappearance of myosin monomer was accompanied by a concomitant increase in polymer content and that the gel strength of enzyme-treated protein was greater. The polymerization could occur at temperatures as low as 4°C, thus opening up possibilities for the manufacture of new products.

Summary

This is a work-in progress.  As I expand the functional value of different MDM or related products, I will add it to this document.  It is an adventure in discovery!

Reference

Hudson, B. J. F. (Editor). 1994. New and Developing Sources of Food Proteins. Springer – Science + Business Media. (Poultry – the versatile food by JM Jones)

EFSA Panel on Biological Hazards (BIOHAZ). 2013. Scientific Opinion on the public health risks related to mechanically separated meat (MSM) derived from poultry and swine; European Food Safety Authority (EFSA), Parma, Italy; EFSA Journal 2013;11(3) : 3137.

  Poultry MDM: Notes on Composition and Functionality Poultry MDM: Notes on Composition and Functionality by Eben van Tonder 5 July 2020 Background The mechanical deboning of meat has its origins from the late 1940s in Japan when it was applied to the bones of filleted fish.