Application of electro-hydraulic shock waves for the disintegration of biological tissues on the example of beef tenderization

Forschungskreis der Ernährungsindustrie e.V. (FEI, Godesberger Allee 142-148 53175 Bonn)

Coordination: Forschungskreis der Ernährungsindustrie e. V. (Research Group of the German Food Industry) (FEI), Bonn, Germany

Research institution I: German Institute of Food Technologies (DIL), Quakenbrück (Dr. V. Heinz/Prof. Dr. S. Töpfl)

Research institution II: Max Rubner Institute (MRI), Federal Research Institute for Nutrition and Food, Analytics Working Group, Kulmbach, Prof. Dr. Dr. F. Schwägele

Industrial partners: Association of the German Meat Industry (VDF), Bonn; Research Curatorship Mechanical Engineering (FKM), Frankfurt; VDMA, Frankfurt

Project coordinator: Dipl.-Ing. D. Stachetzki, Association of the German Meat Industry (VDF), Bonn, Germany

Project period: 2008 – 2011

Grant: € 450,000 (sponsoring through BMWi via AiF/FEI)

BACKGROUND

The quality of meat is defined by various sensory, nutritional, hygienic/toxicological and processing properties. From the customers’ point of view, the appearance, color, odor and taste as well as – for beef, in particular – the tenderness of the meat are decisive quality factors. Increasingly, a shift in the market towards ready-to-cook, easy-to-prepare products can be observed. This results in a growing demand for meat cuts that can be used as steaks or for stir-frying. In dual-purpose cattle, the proportion of meat that can be used for that purpose is significantly lower than in cattle reared for meat production only. The percentage of cuts of the desired quality can be increased by post-mortem ripening. Depending on the age of the cow at the time of slaughter and the proportion of tissue, the ripening period will be 7 days for veal and about 14 days for beef. From an economical standpoint, a reduction in the ripening period and an improvement of the meat quality is desirable, in particular for less valuable cuts.

The objective of this research project was the development of a mechanical process to accelerate the ripening through the use of electro-hydraulically generated shock waves and the resulting disintegration of the tissue.

RESEARCH RESULTS

Within the scope of the project, an experimental model for the generation of electro-hydraulic shock waves has been developed and implemented. Utilizing the discharge between two electrodes or an exploding wire under water, the electrical energy stored in a capacitor bank can be transformed into mechanical energy. The packed meat products are treated in a vessel with an 80 cm diameter that is filled with water. It is necessary to wrap the product in order to avoid contact with the water and to prevent any possible resulting contamination. The intensity of the shock wave can be adjusted via the charging voltage and this is also dependent on the material and the length of the wire.

Based on the experimental model, the effects of the process on the quality properties of beef have been assessed. Roast beef strands (Longissimus dorsi) were cut into 2.5 cm thick slices and wrapped. Next, they were treated with different shock intensity and a different number of shock waves. At the same time, the influence of pre- and post-ripening at 2 °C for 7 days has also been investigated. The tenderness of the cooked samples was assessed with an Instron instrument and the product quality determined.
The samples were compared to conventionally ripened products (14 days, 2 °C).

The sole treatment with shock waves showed only a minor improvement in terms of tenderization. However, with an additional pre- or post-ripening period of 7 days, the tenderness of conventionally ripened samples (14 days ripening) could be equaled or even improved. No significant difference was found between treatment with a single or multiple set of shock waves. Examination of the effects on the meat quality showed not only large variations but also revealed the influence of the biological raw material. After the shock wave treatment, no change in the proteins was found with electrophoretic analysis. The requirement of pre- or post-ripening shows that secondary reactions obviously also play an important role apart from the immediate mechanical effect.

One main challenge is the damage to the meat packaging materials and the test plant caused by the shock waves. Within the scope of the project, a large number of different packaging materials have been tested for their suitability in shock wave treatment processes. Only TPE packaging materials were found to display sufficient stability; however, they are currently not permitted to be used for food. Added to that, the high energy density of an electro-thermal or electro-detonative generation of shock waves results in extreme wear on the pilot plant which could not be eliminated through various modifications. The use of alternative energy transformation processes (piezoelectric, electro-magnetic) and the breakdown of the required amount of energy into smaller units with a higher repetition rate should be the subject of future investigations.

ECONOMICAL SIGNIFICANCE

The pilot plant developed during the project and the processing conditions show that, in general, it is possible to accelerate the ripening of beef with shock waves. This may contribute to an improvement in performance and compatibility for small and medium sized enterprises. The results indicate that the treatment is linked with low energy costs. However, more research and development, in particular, with respect to systems engineering, is necessary for successful industrial implementation of the process.

Each year, 170 meat processors in Germany produce about 7.5m tons of meat products; approximately 1.25m tons are beef and veal products. The meat processing industry in Germany (1,014 companies) predominantly comprises medium-sized enterprises with approximately 94% of the companies reporting a turnover of below 50m Euros.

Putting this process into practice would also open new business opportunities for the mechanical engineering sector in Germany. 270 companies from the food and packaging machine sector generate an annual turnover of about 8bn Euros with approximately 57,200 employees.

The project was supported within the scope of the “program for promoting joint industrial research (IGF)” by the Federal Ministry for Economy and Technology (via AiF) through the Research Group of the German Food Industry (FEI) (AiF project no 15884 N)..

The contact at DIL for this project is

Prof. Stefan Töpfl