Comparison of methods for the assessment of growth of food spoilage moulds in solid substrates

The objective of the study was to evaluate the general suitability of ergosterol content, CFU, and colony diameters determinations for a range of fungi representing food spoilage moulds for the assessment of their growth on solid substrates, in particular intermediate moisture foods. Sixteen food-borne mould species were inoculated onto DG18 agar overlaid with cellophane, allowing determination of a direct measurement of biomass density weighing. The samples were also evaluated with regard to visible and microscopic colony diameters, total ergosterol content, Thoma counts, viable CFU counts, and so on. The same parameters were assayed in the spore suspensions obtained from those cultures. Data were evaluated by multivariate data analysis using projection methods such as principal component analysis (PCA), showing some groupings among the measured variables, mainly linked to the sporulating/nonsporulating nature of the different species tested. Ratios among the different variables were obtained, compared among the species, and evaluated along time (2-10 days). It was concluded that, as a general rule for all the species, ergosterol content and colony diameters were better correlated to fungal biomass dry weight than CFU counts were. Conversion factors were 0.3-3 microg ergosterol mg(-1) biomass dry weight and 76-227 mg biomass dry weight cm(-2), depending on the species.     

Correlation between morphology and stress—strain properties of three block copolymers i. stress-softening effect

The stress-softening effect, which comes out when SBS three block copolymers are stretched, is taken into consideration and the conclusion is reached that it is due to a disruption of the polystyrene continuous phase, according to the hypothesis of other authors. This conclusion is supported by two kinds of experiments performed on samples having a well known and simple morphology. First of all by stress-strain measurements on specimens previously swollen: it can be seen that the stress-softening effect disappears as soon as the structure of the material is completely modified by the treatment. Secondly by the direct observation at the electron microscope of the structure after the deformation. This shows how the original continuous and regular polystyrene rods of the “single crystal” assume a string of pearl structure which finally is irreversibly disrupted.     

Crystallisation kinetics and morphology of high density polyethylene containing organic and inorganic pigments

Some organic pigments, present in very small amounts (0.1 to 0.2%), can cause warpage and shrinkage phenomena in moulded parts of linear polyethylene. Investigations on such phenomena have been carried out by dilatometric and morphological analysis. The influence on polyethylene crystallisation kinetics and morphology of such organic and inorganic pigments, which do not cause any deformation effect, has been studied. The experimental results show that only organic pigments increase the crystallisation rate, by acting as nucleating agents; in these cases, moreover, the crystalline grain is smaller and the typical morphology of polyethylene crystallised in bulk is altered. A possible correlation between the nucleating action and the warpage effect of organic pigments on moulded polyethylene is discussed.     

A kinetic study of the metathesis of propene on a rhenium-aluminium catalyst

Based on integral kinetic measurements and in accordance with the results of previous investigations, two mechanistic initial rate expressions based on different reaction mechanisms have been found to be statistically equivalent. Applying the Boudart criteria in a test for the physical significance of the parameter estimates, only one of the suggested expressions is significant and the corresponding reaction mechanism is, therefore, considered adequate.     

Characterization of yeast and lactic acid bacterial species in ropy wines

Summary The microflora in ropy sherry-type wines were identified. The genusSaccharomyces were the predominant yeasts (81%), withS. beticus prevailing.Lactobacillus plantarum was the most frequent bacterial species (33.9%), followed byStreptococcus diacetilactis (22%) andS. lactis (16.9%).

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Charakterisierung der Hefe-und der Milchsäurebakterien-Arten in sirupösen Weinen

Zusammenfassung Eine Analyse der Mikroflora in sherryartigen, sirupösen Weinen ergab die Anwesenheit von deckenbildenden Hefen des StammesSaccharomyces (81%), wobeiS. beticus am stärksten vertreten ist. Bei den Bakterienstämmen istLactobacillus plantarum (33,9%) am stärksten vertreten, gefolgt vomStreptococcus diacetilactis (22%) und demS. lactis (16,9%).

     

Production of hot rolled dual-phase steel strip by coiling below martensite start temperature

The laboratory tests showed that a dual-phase steel can be produced on the basis of the chemical composition given here, providing the coiling temperature is below the martensite start temperature. It is then possible to dispense with an additional air cooling period on the runout table, which is mandatory with production concepts known up to now. The best mechanical properties are attained at a coiling temperature of 200°C. The final rolling temperature should be around A_r3 to avoid a heavy ferrite deformation without softening and, on the other hand, to reduce the yield stress increase caused by aging. Nitrogen aging can be suppressed by the addition of small amounts of titanium to bind nitrogen, forming a dispersion of titanium nitrides. The feasibility of this concept under production conditions was confirmed by means of hot rolling tests on a hot wide strip mill.     

Measurements and thermodynamic modeling of the solubility of squalene in supercritical carbon dioxide

The solubility of squalene in supercritical carbon dioxide (SC-CO₂) was measured and it was analyzed together with the values obtained by Catchpole and von Kamp (1997). The results showed that the experimental values obtained in this work agreed with the order of magnitude of those reported in the literature and correlated well with the Chrastil equation. The thermodynamic modeling using the Peng–Robinson equation of state only correlated well with the experimental values obtained when the critical properties and acentric factor reported by Ruivo et al. (2004) were used. The values predicted for the solubility of squalene in SC-CO₂ using modeling employing the GC-EOS, were only of the same order of magnitude as the experimental values for pressures below 200 bar, and its performance was influenced by the value of the critical hard sphere diameter.     

Species,roasting degree and decaffeination influence the antibacterial activity of coffee against Streptococcus mutans

Coffee beverage has been associated with antibacterial activity against Streptococcus mutans, a cariogenic bacterium. This study aimed at identifying natural compounds in coffee that contribute to such activity and investigate the influence of species, roasting and decaffeination on it. Coffee chemical compounds and aqueous extracts of green and roasted regular and decaffeinated Coffea arabica and Coffea canephora beans were tested. MIC, biofilm inhibition and biofilm reduction results were correlated with the concentration of coffee compounds in the extracts. 5-Caffeoylquinic acid, trigonelline and caffeic acid solutions showed bacteriostatic activity (MIC = 0.8 mg/mL). Lighter and regular extracts showed higher inhibitory activity than darker and decaffeinated extracts, with an inverse correlation between bacterial colony-forming units and roasting degree. Only regular C. canephora extracts showed biofilm formation inhibition. The joint effect of chlorogenic acids, trigonelline and caffeine or other compounds removed by decaffeination seems to be one of the causes for coffee antibacterial activity against S. mutans.     

Combined effect of enterocin AS-48 and high hydrostatic pressure to control food-borne pathogens inoculated in low acid fermented sausages

The single and combined effects of enterocin AS-48 and high hydrostatic pressure (HHP) on Listeria monocytogenes, Salmonellaenterica, and Staphylococcus aureus was investigated in fuet (a low acid fermented sausage) during ripening and storage at 7 °C or at room temperature. AS-48 (148 AU g⁻¹) caused a drastic 5.5 log cfu g⁻¹ decrease in L. monocytogenes (P < 0.001) and a significant (P < 0.01) inhibition (1.79 logs) for Salmonella at the end of ripening (10 d). After pressurization (400 MPa) and storage Listeria counts remained below 5 cfu g⁻¹ in all fuets containing AS-48 (pressurized or not). HHP alone had no anti-Listeria effect. HHP treatment significantly reduced Salmonella counts, with lowest levels in pressurized fuets with AS-48. S. aureus showed similar growth for all treatments and storage conditions. These results indicate that AS-48 can be applied alone to control L. monocytogenes and combined with HHP treatment to control Salmonella in fuets.     

Double-muscling character influences the trans-18:1 and conjugated linoleic acid profiles in concentrate-fed yearling bulls

Seventy-five yearling bulls of the “Asturiana de los Valles” northern-Spanish beef breed (double-muscled, mh/mh, n = 24; heterozygous, mh/+, n = 26; normal, +/+, n = 25) were produced under intensive conditions and the effects of double-muscling genotype on trans-18:1 and CLA isomer profiles were examined. Total trans-18:1 contents, measured as percentages of total fatty acid methyl esters, were 10.98–15.07% in backfat and 8.64–9.46% in muscle, and the major isomer was 10t-18:1 in all animals. In mh/+ animals, 11t-18:1 was the second most abundant trans isomer in muscle whereas in mh/mh and +/+ animals 11t-18:1 and 13t/14t-18:1 were relatively similar. Total CLA percentages were 0.71–0.85% in backfat and 0.32–0.40% in muscle. The highest total CLA percentage found was in mh/+, intermediate in +/+ and lowest in mh/mh animals (P < 0.05). Heterozygous animals had significantly higher percentages of 9c,11t- (P < 0.01), 11t,13c- (P < 0.01) and 9c,11c-18:2 (P < 0.05) and also significantly higher percentages of the sum of 9c,11t-/11t,13c-/11t,13t-18:2. Overall, mh/+ animals produced meat with a slightly better trans and CLA profile (i.e., less 10t-18:1 and more 11t-18:1 and 9c,11t-18:2) than other genotypes, however, further improvements would still be necessary to achieve a profile with a positive health image.