Mechanical properties and water vapor permeability of starch/montmorillonite nanocomposites

Results of an investigation into an unmodified‐montmorillonite (MMT)‐filled nanocomposite based on plasticized starch are reported. Data on the influence of MMT content on the tensile mechanical properties of the material are presented. Particular attention is given to the water vapor permeability of the nanocomposite. It is found that the resistance to water permeation of plasticized starch can be improved considerably by introducing a rather small amount of the filler into it. Data on the influence of MMT content on the coefficients of moisture diffusion, solubility, and permeability are reported. Also, a simple method for determining the effect of irregularly oriented platelike filler particles on the permeability of the composite material is suggested. The calculation results are compared with experimental data. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Solid propellant burning rate measurement in a closed bomb

Experiments show that the burning rate of solid propellants is a function of the pressure under which the burning takes place. An often used method to determine that burning-rate function is to burn a sample of the propellant in a closed container and to register the corresponding pressure time data. With the aid of formulas from thermodynamic theory, these observations can be manipulated to yield the desired parameters of the burning-rate function. This analysis is typically done under a number of restrictive assumptions, e.g., the assumption of constant temperature in the container throughtout the experiment. In spite of such assumptions, the corresponding algorithms published are complicated, and an error analysis of the results has apparently never been reported. In the present paper, new formulas are derived under relaxed assumptions. With the aid of these formulas the data analysis is reduced to a curve-fitting task. For such tasks standard theories and computer programs are available, which furnish the unknown parameters of the burning-rate function together with estimates of their variances and covariances. The new formulas can be replaced by simpler ones under certain conditions, which are controllable by the design of the experiment. It is found that for such simplifications the temperature behavior is not relevant. In general the simplifications are permissible if the maximum pressure achieved during the experiment remains essentially smaller than the chemical energy released per unit volume of the propellant. The latter is typically of the order of 10¹⁰ Par (10⁵ atm). An example illustrates the application of the new algorithm.     

High occurrence rates of enrofloxacin and ciprofloxacin residues in retail poultry meat revealed by an ultra-sensitive mass-spectrometric method,and antimicrobial resistance to fluoroquinolones in Campylobacter spp

An ultra-sensitive mass spectrometric confirmation and quantification method for the determination of selected fluoroquinolones—enrofloxacin and its main metabolite ciprofloxacin—was developed and validated in poultry meat samples. The achieved limits of quantification were 1 ng kg^?1 for enrofloxacin and 10 ng kg^?1 for ciprofloxacin. The analysis of 40 retail poultry samples originating from Estonia, Latvia, Lithuania, Poland and France revealed that 93% of samples contained residues of enrofloxacin in the range from 3.3 to 1126 ng kg^?1. Previous studies have shown high levels of antimicrobial resistance to fluoroquinolones, particularly in Campylobacter spp. and various faecal indicators isolated from broiler meat. Consequently, the revealed widespread usage of fluoroquinolones in the poultry industry may result in the further emergence of antimicrobial resistance of Campylobacter in the food chain.     

Contamination patterns of Listeria monocytogenes in cold-smoked pork processing

Contamination patterns of Listeria monocytogenes were studied in a cold-smoked pork processing plant to identify the sources and possible reasons for the contamination. Environmental sampling combined with pulsed-field gel electrophoresis (PFGE) subtyping and serotyping were applied to investigate the genetic diversity of L. monocytogenes in the plant environment and ready-to-eat (RTE) cold-smoked pork products. A total of 183 samples were collected for contamination analyses, including samples of the product at different stages during manufacture (n = 136) and environmental samples (n = 47) in 2009. L. monocytogenes isolates, previously recovered from 73 RTE cold-smoked pork samples and collected from the same meat processing plant in 2004, were included in this study. The brining machine and personnel working with brining procedures were the most contaminated places with L. monocytogenes. The overall prevalence of L. monocytogenes in raw pork (18%) increased to 60% after the brining injections. The brining machine harbored six different PFGE types belonging to serotypes 1/2a, 1/2c, 4b, and 4d, which were found on the feeding teeth, smooth surfaces, and spaces of the machine, thus potentially facilitating dissemination of L. monocytogenes contamination. Two PFGE types (2 and 8) belonging to serotypes 1/2a and 1/2c were recovered from RTE cold-smoked pork collected in 2004, and from surfaces of the brining machine sampled in 2009, and may indicate the presence of persistent L. monocytogenes strains in the plant. Due to poor hygiene design, removal of the brining machine from the production of cold-smoked meat products should be considered to reduce L. monocytogenes contamination in the finished products.