In Germany, scientists have modified a chemical process better known in textile manufacture to create a new generation of sausage skins. Meanwhile, Welsh researchers have a new rapid detection technique for contamination of meat products.
Every year millions of sausages are consumed around the world. On average, each German gets through about 70grams of such meat every day.
However, keeping the product in shape remains one of the biggest challenges for the sausage industry. Today, most come wrapped in an artificial skin known as a casing. Often these are made of regenerated cellulose, a synthetic material with entirely natural properties, commonly known as cellophane foil or in its fibrous form as Cordura, Tencel, rayon and viscose (artificial silk).
Now scientists at the Fraunhofer Institute for Applied Polymer Research IAP in Golm near Berlin have developed a new and now patented process with which blown cellulose film can be manufactured also for use as sausage casing.
This new technology is based on the relatively new Lyocell process. Here, chemical conversion pulp is dissolved in a mixture of water and N-methylmorpholine-N-oxide. This solution is extruded in a regenerating bath where the solvent is released and can be returned almost entirely to the process. As a result, this technique is less complicated than existing methods using chemical conversion steps.
"With our method, the cellulose solution is extruded through a ring nozzle. But it does not immediately enter the regenerating bath. First it passes through an aair gap', in which lateral and longitudinal strength characteristics of the tube are set by internal air pressure. As with regular cellophane, the films are made of pure cellulose and are as biodegradable as wood,“ said project head Peter Weigel when explaining the merits of IAP's new process.
"It is worth noting that what we have done for the first time is to demonstrate and patent the blow extrusion technique for manufacturing tube-like cellulose films. So we can overcome the disadvantages associated with processing cellulose when compared with synthetic polymer films derived from materials such as polyethylene and polypropylene,“ Weigel told European Food Scientist.
Together with one of the market leaders for cellulose sausage casings, Belgian company Teepak, the work of the IAP researchers over the past three years began with a laboratory process and has now led to a pilot plant on a semi-industrial scale.
The manufacturing process is both ecological and cost-effective. Alteration of specific technical parameters enables the scientists to manufacture casings with varying but defined properties. Head of research Hans-Peter Fink said: "The degree of porosity, for example, determines how fast flavorings can penetrate the casing. This is particularly important in smoking and cooking sausages. Furthermore, the surface structure of the casing mainly influences the atightness' or adhesive strength to the sausage meat.“
As well as sausage casings, the Fraunhofer scientists are also investigating other uses for their new material. These include packaging foils and membranes for use in separation processes.
Rapid contamination detection
Researchers at the University of Wales, Aberystwyth (UWA) have developed a new rapid procedure which will enable food producers to detect the bacterial contamination of their meat products.
Their findings, recently published in Applied and Environmental Microbiology, demonstrate a novel analytical approach that can enhance and accelerate the detection of microbial spoilage, providing rapid, accurate and quantitative results in real time so that appropriate corrective action can be taken as soon as possible.
Roy Goodacre and David Ellis in the Institute of Biological Sciences at UWA have used Fourier transform infrared (FT-IR) spectroscopy to produce a `fingerprint` of the biochemical changes that occur on the surface of chicken breast meat as a result of the growth of microorganisms. These metabolic changes result in a number of organoleptic features that make the meat unacceptable to the consumer, including changes in appearance (discoloration), the development of off-odours, slime formation, or changes in taste.
"Whilst the activity of enzymes present in muscle tissue post-mortem can contribute to a number of changes during storage, it is generally accepted that detectable organoleptic spoilage is a result of decomposition and the formation of various metabolites caused by the growth of microorganisms,“ said Goodacre.
"We have used spectroscopic analysis to exploit this information so that, rather than measuring exclusively the presence of bacteria per se on the meat surface, infrared can be used to measure the biochemical changes within the meat substrate, enhancing and accelerating the detection of microbial spoilage. We have developed horizontal attenuated total reflectance (HATR) FT-IR spectroscopy with the most appropriate machine learning algorithms for estimating the bacterial total viable count directly off the surface of muscle foods. The effectiveness of this technology has been established through a detailed investigation of the natural spoilage process on chicken breast muscle. In addition, this technique is also very rapid (taking a few seconds) compared to hours to days by conventional means,“ he added.
The last decade has seen an exponential increase in the consumer demand for poultry and poultry products, fuelled in part by dietary health considerations and the recent BSE and foot and mouth crises. Fears over microbiological food safety issues, especially the incidence of Salmonella and Campylobacter, in conjunction with consumer demand for a product of consistently high quality, have focused attention on a particular area of the food production industry, namely the requirement for a rapid (less than a few minutes) and accurate detection system for microbiologically spoiled or contaminated meat.
At present no such technology exists in the food industry within the Hazard Analysis Critical Control Point (HACCP) system for the routine microbiological safety and quality of meat and poultry products.
"To date, more than 40 methods have been proposed to measure and to detect bacterial spoilage in meats. The major drawback with these is that they are time consuming, labour intensive and give information about contamination retrospectively some considerable time after it has happened, and often when it is too late to take corrective action,“ added Goodacre,
"Since the ideal method for the on-line microbiological analysis of meat would be rapid, non-invasive, reagentless and relatively inexpensive, we feel that these requirements can all met by the application of this spectroscopic approach. Now that we have established this methodology, our next goal is to test how our approach may aid both food safety regulatory bodies and the HACCP system,“ he concluded.
