Author: Marielle Ramaekers
TWO WAYS OF APPLYING PRESSURE IN MEAT PROCESSING
Use of High pressure processing effectively inactivates microorganisms without heating in meat and meat products. Shockwaves tenderizes the meat. Both gentle processes improve the structure and pave the way for developing new foods, for example low salt foods or meat products with increased nutrients.
Pressure can be applied by high pressure processing (HPP), or by hydrodynamic pressure in the form of shockwaves (HDS). HPP has become an industrial reality for the meat industry within the past twenty years. Shared use of HPP equipment makes the technology accessible for small and medium enterprises. HDS is a promising technique for tenderizing meat. A newly developed prototype awaits its first application.
High pressure processing (HPP)
High pressure processing (HPP) is a novel post-packaging technology that effectively inactivates microorganisms without heating. Commercially it is used in cases where heat treatment is not possible or not convenient. Sensitive resources such as vitamins and other nutritional ingredients are retained. It is also a novel strategy to successfully alter the structure and other quality parameters of meat and meat products, such as colour and water holding capacity.
HPP can tenderize meat, but this depends on the rigor stage, pressure and temperature level applied. For example, pressures below 200 MPa can tenderize pre-rigor meat, whereas tenderization post-rigor with HPP can only be achieved by higher temperatures.
HPP can enhance gel structure and water binding capacity and can therefore be useful in product development. Muscle proteins, including myofibrillar proteins, are unfolded up to a pressure of 300 MPa. Pressures above this level result in increased denaturation, gel formation and agglomeration of proteins. For example in fresh meat, the application of low pressure levels can be used to improve the functional and rheological properties of PSE meat or turkey meat with low pH.
Vitamins, protein functionalities and overall the freshness are retained by using HPP, which is often not the case during heat treatments. Also, HPP can be used to develop meat products with reduced salt content. Salt is typically added to improve protein hydration, but hydration is also improved by HPP treatment due to protein unfolding. HPP has already been used to reduce cook loss and to improve the texture of low-salt beef sausage batters.
Improved shelf life
The commercially applied pressure levels range between 400–600 MPa with short processing times of 3–7 min at ambient temperatures. In most cases this leads to a 10,000-fold reduction in the majority of pathogenic and spoilage microorganisms, resulting in an increased shelf life and improved safety. The inactivation of microorganisms depends on process parameters such as pressure, temperature and processing time and on product parameters such as pH, water activity, salt content and the presence of other antimicrobials.
Examples of HPP foods
The production of liver sausage results in a significantly smoother and homogenous product with an increased liver-taste when replacing two thermal steps by HPP. In addition, time and energy consumptions and nutritional value are significantly improved. Other examples of products currently processed with HPP are: fermented sausages, filet American, steak tartar, Carpaccio, hamburger, deli meats infused with extra virgin olive oil, poultry strips, oven roasted chicken, meat and cheese snack products, Serrano ham and chorizo.
Hydrodynamic pressure can be used to control and improve the tenderness of meat
Overcoming undesired changes
HPP affects the colour and texture of meat, depending on the pressure level that is applied. The meat becomes more gel-structured and paler, losing the typical appearance of fresh meat. Colour changes are more significant for fresh red meat than for white meat and cured meat products. Undesired changes can be limited by changing the process parameters, such as pressure, time and temperature. In addition, curing, oxygen removal and the increase of pH by changing the ingredients of a meat product can limit changes in colour.
Europe’s HPP facilities
Consumer acceptance of HPP is high in comparison to other non-thermal decontamination technologies such as ionizing radiation, leading to an increased number of commercial installations. Some companies have their own facilities, but others share or use toll processing. For example, DIL in Germany and Cluster FOOD + i in Spain offer HPP toll processing in combination with process and product development. When you like to hear more about the facilities in your neighbourhood, you can contact your local hub advisor of the TRADEIT project.
Hydrodynamic shockwave (HDS) use has emerged in the recent years as a suitable option, specifically when a consistent quality and tenderness of meat cannot be reached by the existing technologies. HDS uses underwater pressure pulses that instantaneously develop shockwaves up to 1 GPa pressure in a fraction of milliseconds. HDS induces mechanical tissue disintegration and therefore tenderizes meat. It can also be used to shorten the time to tenderize meat. It is not clear what effect HDS has on inactivation of microorganisms. The German Institute of Food Technologies DIL developed a first industrial prototype. Due to the continuing design and building of new process equipment for the generation of shockwaves, it is expected that the use of HDS will become an industrial reality in the near future.
Processing of tougher meat types such as buffalo meat is a viable option for hydrodynamic shockwave treatment
Examples of HDS foods
The technique provides tenderness improvement for lower quality cuts such as round or flank meat or meat from dairy cattle breeds. HDS allows a quality improvement and a reduction of maturation time. Also processing of tougher meat types such as buffalo meat is a viable option.
The costs for applying HPP depend on the specific product and process parameters, especially the filling ratio, but are around 0.10 €/kg, if you would apply 600 MPa, 5 min at room temperature for pasteurization. Sterilisation with HPP in combination with high temperature is not implemented yet, but costs are estimated to be at least 0.30 €/kg for 600 MPa, 120°C, 3 min. Shock wave costs are difficult to estimate, as the technology is not ready yet, but fast progressing. Optimization of process parameters is required per particular application. The German Institute of Food Technologies (DIL) can help you further (www.dil-ev.de).
This article is adapted from "Quality considerations with high pressure processing of fresh and value added meat products", published in Meat Science 92, 2012 and authored by Bajo Bajovic, Tomas Bolumar and Volker Heinz.