Development of low density polyethylene nanocomposites films for packaging

Requirements for adequate permeability of polymeric materials to gases and vapors, good barrier and mechanical properties of polymers have boosted interest in developing new strategies to improve these properties. Research and development in polymeric materials coupled with appropriate filler, matrix-filler interaction and new formulation strategies to develop composites have potential applications in various types of packaging (agricultural produce, dried food, frozen food etc.). In this study, LDPE composites containing various types of fillers (zeolite TMAZ 7, nanoclay Cloisite 20A and precipitated calcium carbonate, CaCO₃) were prepared using extrusion/injection molding. The microstructural and morphological changes as well as mechanical features of samples were characterized by scanning electronic microscopy and by tensile tests. The thermal degradation of LDPE composites was studied using thermogravimetric analysis. Barrier properties (permeability, the diffusion and the solubility constant) in modified LDPE samples were determined. It is found that used minor clay concentration is already very effective for achievement of good morphology. In the presence of nanoparticles, at lower content, the value of oxygen permeability of LDPE decreases. Also, the results have revealed that the samples containing fillers have increased thermal stability in comparison to pure LDPE.     

Correlation of Mycobacterium avium subsp. paratuberculosis counts in gastrointestinal tract, muscles of the diaphragm and the masseter of dairy cattle and potential risk for consumers

Tissues of cattle intended for human consumption can be contaminated by Mycobacterium avium subsp. paratuberculosis (MAP). Although different studies attribute varying roles of MAP in Crohn's disease progression it is thought that the exposure of humans to this bacterium should in any case be minimised. In this study, we have collected samples of intestine, mesenteric lymph nodes, muscles of diaphragm (musculus diaphragma) and masseter muscles (musculus masseter) from twenty-five cows in a slaughterhouse. The infectious status of all animals was confirmed by culture of faeces. MAP was found in almost all the intestines and mesenteric lymph nodes examined, including three faecal culture-negative animals indicating intermittent shedding. As intestine is used for the traditional production of sausages, it is alarming that 84.2% of intestine samples were positive for MAP. F57 and IS900 real time PCR revealed MAP in 40 to 68% of diaphragms and 11.1 to 38.9% of masseters. A noticeable dependence of the probability of MAP positivity of faeces versus gastrointestinal tract (GIT) and of GIT and muscles was observed. Due to the changing behaviour of consumers, both of these muscles have started to be widely used in cuisine. Therefore, the results of this paper imply that the processing of cows with paratuberculosis in abattoirs without any precautions (restrictions) and the usage of meat for human consumption should be rethought.     

On-farm spread of Mycobacterium avium subsp. paratuberculosis in raw milk studied by IS900 and F57 competitive real time quantitative PCR and culture examination

A rapid, cheap and sensitive detection method of Mycobacterium avium subsp. paratuberculosis (MAP) in raw milk was needed for routine usage. We developed two duplex real time qPCR systems specific for MAP detection. These real time qPCR assays amplify the multicopy element IS900 for qualitative analysis and the single copy element F57 for quantitative analysis. Both assays incorporate an internal amplification control amplified with the same primers as the targets and the same probes are used in both assays. The specificity of the assays was confirmed by the testing of 6 different MAP isolates, 12 isolates of other mycobacteria or bacterial species and 4 different mammalian DNAs. The sensitivity of the developed assays and isolation efficiency were demonstrated through the analysis of raw milk samples artificially contaminated with MAP cells and with plasmids containing cloned fragments of the targets (IS900 and F57). The developed assays for milk analysis were applied to samples from one farm with two faecal shedding cows. Three hundred and forty five individual milk samples were tested by real time qPCR assays and by cultivation. Hundred and eleven (32.5%) individual milk samples were positive by the real time qPCR, no milk sample was culture positive. The spread of MAP in individual, tank and bulk tank milk samples was also monitored.     

The zinc-chlorine battery: half-cell overpotential measurements

The voltaic performance of the zinc-chlorine battery was investigated by measuring the individual potentials of the Zn and Cl₂ electrodes versus a reference electrode. The overpotential at the Zn electrode is very small for both the charging and the discharging processes, and the use of a flow-through porous Cl₂ electrode is advantageous. Energy efficiency in the region of 65% has been achieved for a complete cycle. Tafel polarization data for both the zinc and the Cl₂/graphite electrodes was obtained using rotating zinc hemisphere and graphite disc electrodes. Exchange current densities and Tafel slopes are reported.     

Redox-potential and browning of tomato paste in aluminium tubes during storage at different temperatures

The influence of temperature and applied lacquer on aluminium (Al) tubes on physico-chemical changes of tomato paste during storage was studied. Packaging and storage conditions have a considerable influence on both the oxidative changes in the product and corrosion behaviour of the Al tubes. The greatest changes during storage were the ascorbic acid and hydroxymethylfurfural contents; the compounds known to possess certain oxido-reduction power. The consequence of oxidation-reduction reactions taking place during storage was the establishment of particular redox values: the lower the reducing power of the compounds present, the higher the rH value obtained.

---

Braunwerden und Redoxpotential des Tomatenkonzentrates bei verschiedenen Lagerungstemperaturen

Zusammenfassung Es wurden der Einfluß der Temperatur und der Alu-Verpackung auf physikalisch-chemische Änderungen des Tomatenkonzentrates während der Lagerung untersucht. Dabei wurde festgestellt, daß die Verpackung und die Lagerungsbedingungen auf die oxydativen Veränderungen des Tomatenkonzentrates und der Korrosionsprozeß in der Alu-Verpackung einen großen Einfluß haben. Die größte Änderungen während der Lagerung wurde im Gehalt an Askorbinsäure und Hydroxymethylfurfural festgestellt. Die genannten Verbindungen haben gewisse Redox-Eigenschaften. Die Redox-Reaktion während der Lagerung hat Einfluß auf die Veränderung des Redox-Potentials, und zwar ist dieses um so höher, je niedriger die Reduktionskraft der anwesenden Verbindungen ist.

     

Survival of three Mycobacterium avium subsp. hominissuis isolates in fish products after hot smoking and frying

Fish mycobacteriosis should be considered as one possible means of transmission of mycobacterial infections to humans. In our study, we examined the survival of three field Mycobacterium avium subsp. hominissuis (MAH) isolates in fish meat during thermal processing technologies using culture and quantitative real‐time PCR (qPCR) methods. Minced carp meat mixture was artificially contaminated with known amount of MAH cells and survival and absolute numbers of MAH was monitored after hot smoking and frying. The viability of MAH was significantly lower after the frying process, whereas in response to hot smoking viable MAH cells could still be cultured even after 10 min at 70 °C. Significant differences in thermal stability were also observed among the three different MAH isolates. The human isolate was the most resistant, whereas the environmental isolate was the least resistant, which is probably due to host adaptability. In this work we confirmed that MAH can survive temperatures of 70 °C and thus can pose a risk to consumers.     

Environmental aspects and economic evaluation of new green hydrolysis method for waste feather processing

Clean Technologies and Environmental Policy - In recent years, an increase in the chicken meat process industry has been growing quickly, which brings a large amount of difficult to process waste,...