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Focus on meat quality

The 46 th Kulmbach Week presented by the Max Rubner-Institute (MRI) in Kulmbach was dedicated to the improvement and preservation of quality and safety in meat and meat products. In 18 lectures, the research institute’s scientists as well as researchers from the Czech Republic, Serbia and Russia presented the newest results of their work.

The introduction to the conference revealed current findings on the variability of tissue ratios in pork, which led into the first major topic of the conference, “Meat output and quality”.

Detailed information on tissue composition of pork carcass halves is of major significance for judging the quality of the carcass, as basic data for breeding as well as a guiding principle for processing. Extensive cuts of representative samples from the pork population in Germany have determined averages of 58 percent lean meat, 24 percent fat and ten percent bone. Compared to previous values, this is a reduction in fat of circa three percent by the same proportion of bone. Of the entire lean meat in pork carcasses, ham has a proportion of 32 percent, cutlets 17 percent and the shoulder 16 percent. These relative values vary little, as scientists could demonstrate. This shows that an increase in the proportion of lean meat cannot be achieved via a shift in body proportion, but only via a shift in tissue relationships.

A team of Russian scientists from the VNIIMP Meat Research Institute in Moscow is working on modern histological methods for determining meat composition. Team members found that certain vegetable and animal materials used during the meat manufacturing process can be reliably detected, regardless of the material or the processing technology. In their lecture, they discussed methods for determining the counterfeiting of raw materials and judging their quality. These methods are for the most part already part of the national standards of the Russian Federation.

In addition, the Russian scientists also concluded through an investigation that meat quality can be improved among other things, through feed, stalling and animal transports to slaughterhouses as well as through the use of special technologies and treatment of animals, which also enables efficient production of healthy foods. Enrichment of micro- and macro-elements in animal organs and tissue through feed supplements provides increased nutrients for humans. In this context of the food chain, the animals act as a type of buffer in the transmission of micro-nutritional elements by eliminating toxic risks for the population and simultaneously covering the needs for these micro-elements. Feed has thus proven to be an optimal instrument for achieving the required functional-technological meat characteristics. It is thus recommended to change the focus from optimal nutrition for humans to optimal feed for animals, which will serve to keep domestic animals healthy, prevent disease, achieve optimal breeding characteristics and produce high-quality animal products with specified characteristics.

A question of definition

Mechanical deboning of poultry carcasses and pieces increasingly raises definitional problems. Advancements in automated cutting and deboning of poultry carcasses is leading to the fact that manual deboning is now rare, which reduces the boundaries between the production of fresh meat and the production of residual meat, technically speaking. But if the principle of mechanical production of residual meat can often no longer be used as a decisive exclusion criterion for defining fresh meat, the significance of other legal criteria [VO (EG) 853/2004 Annex 1] is increasing. These include microbiological threshold values, calcium content or bone particle content as well as the degree of change in the muscle structure.

While ideas about the other criteria are for the most part uncontested, however, fundamental insights on histological evaluation of muscle structure are missing. In view of this situation, Dr. Wolfgang Branscheid presented the results of an experiment intended to develop the possibilities of histomorphological evaluation of mechanically as well as manually deboned poultry meat and mechanically gained residual meat.

The mechanically and manually deboned meat samples were analyzed for their most important contents (complete analysis, BEFFE, Ca) and subjected to morphometric determination of bone and cartilage particles.

Chemical analysis gave the expected results. The highest fat content was found – regardless of the processing method – in chicken drumsticks (with skin) and the backs as well as the separator meat. Apart from the separator meat, the back pieces and pre-separated chicken bones had the highest calcium content. The separator meat contained the highest content of bone and cartilage particles. Altogether, the share of cartilage particles in the examined samples was higher than the bone particles.

Histomorphological examination enabled a clear demarcation of gentle deboning procedures in contrast to separator meat. Aided by the preparation of morphological standards for the gradually differing structural changes, a first attempt was taken to make the histomorphological evaluation more reproducible.

Pre-packaged raw sliced ham

The 46th Kulmbach Week took a thorough look at the technological and sensory quality of pre-packaged raw sliced ham. The development from the meat counter to pre-packaged, portioned slices and cubes of raw ham has led in part to changed manufacturing procedures, and in the course of this, to changed sensory qualities. The majority of pre-packaged wares is characterized by a greater surface area and moderate dryness at very long shelf-life times.

The desire to keep the size and form of raw ham as uniform as possible is leading to the fact that unprocessed pieces of rolled, smoked pork loin as well as bacon are joined together in larger units and stabilized using thickening agents, artificial casings or compression equipment.

A new trend is the marketing of raw ham products out of such meat like poultry – a process similar to that of formed meat. However, the processes used to stabilize formed meats, such as treatment with heat or freezing, are not used for these types of raw ham products. To hold together these types of individual pieces in the end product, structure-forming enzymes as well as certain “glues” consisting of alginates, starch, protein or enzymes come into play, according to the scientists.

Although pre-packaged ham is becoming increasingly popular, there has been no systematic investigation of their microbiological safety and quality until now. The Kulmbach scientists have recently been able to close this gap. All in all, their results showed that in regard to two essential microorganisms, L. monocytones and S. aureus, pre-packaged sliced raw ham products made by German manufacturers are microbiologically safe and generally have adequate shelf-life dates.

Effects of additives

Further lectures dealt with various additives, especially artificial colorings and their effects as well as the detection of these substances. Because sausage color is a very important evaluation criterion, the color of meat products was discussed in detail. Aside from the addition of coloring agents, including spices like paprika, the concentration of hemoglobin, technological processes and storage conditions are also important for the intensity of a red color in meat products. Numerous chemical reactions in meat products that affect the oxidation of hemoglobin, in particular lipid oxidation, also influence their color.

As Czech scientists could show at the Kulmbach Week, this oxidation process can be retarded by the addition of spice extracts with antioxidant properties. Sage, oregano and rosemary extracts are typically used in this context. The effect of these spice extracts is many times higher than that of synthetic antioxidants.

The analysis of metabolites

A fairly new research area is the examination of the products of metabolism in their entirety in a product or organism: the so-called metabolome. In a joint project between the Analytik working group and the Institute for the Safety and Quality of Milk and Fish at the Max Rubner Institute, quality-relevant metabolic products such as free amino acids were investigated in fish, meat and milk. The lecture focused on the nutritional significance of the metabolome content and its contribution to estimating the intake, with a primary focus on food. Especially interesting from the nutritional point of view is the free amino acid taurin, which among other things plays a role in the development of the central nervous system. It was first analyzed in pork, milk, trout and carp samples in this project, which began in September 2010. Carp meat showed relatively high levels of taurin.

Among the undesirable elements that develop when food is heated is 3-MCPD (3-Monochlor-1.2-propandiol). Animal experiments have showed that this substance can cause tumors when present in higher doses. Maximum levels for some foods have already been defined; levels are in planning for other foods. A research project by the Analytik working group of the MRI is helping accumulate the necessary data for this. Among other things, MRI scientists also investigated the formation of 3-MCPD when barbecuing pork neck steaks under different conditions (e.g. charcoal, gas and electric grills). Until now, depending on these conditions, 3-MCPD contents of between 3 µg and 380 µg per kilogram have been found.

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