Redox processes in pressurised smoked salmon studied by resonance Raman spectroscopy

Non-thermal food preservation technology is based on the application of high pressures up to 600 MPa. Here we report a resonance Raman (RR) spectroscopic analysis of smoked salmon meat after high pressure processing. High quality spectra, which can be obtained even from packed salmon without spectral interference of the packing foil, allow determining pressure-dependent irreversible changes of the main RR-active components of salmon meat, astaxanthin and myoglobin/haemoglobin. High pressure-treatment causes a decrease of the relative RR intensities of astaxanthin as probed with 514 nm excitation which is in line with a slight attenuation of the originally intense red colour of the salmon meat. 413-nm excited RR spectra indicate a heterogeneous broadening of astaxanthin bands accompanied by the formation of deoxy-myoglobin or deoxy-haemoglobin. The results suggest that pressure-treatment facilitates the oxidative degradation of astaxanthin coupled to the reduction of metmyoglobin (methaemoglobin).     

L?slichkeit und gel-elektrophoretische Muster hitzedenaturierter Proteine, auch von st?rkehaltigen Proben, nach Einwirkung von Na-dodecylsulfat (SDS)

Zusammenfassung Das Lösungsvermögen des Anionendetergents Na-dodecylsulfat (SDS) in Gegenwart disulfidbrückenspaltender Reagentien auf native und auf hitzedenaturierte Proteine wird an Fleisch-und Kartoffelproteinen mit Hilfe elektrophoretischer Methoden untersucht. Die zur Resolubilisierung notwendige Menge an SDS und die erforderliche Incubationszeit werden für die verschiedenen Proben ermittelt. Die Proteine des Skeletmuskels von Rind, Schwein, Huhn und Pute einerseits und die Proteine der europäischen Kartoffelsorten und der südamerikanischen Primitivkultivare andererseits zeigen in der SDS-PAGE ein sehr ähnliches Bandenmuster, das speziesdifferenzierend kaum ausgewertet werden kann, aber ein gutes Charakteristikum für Muskel-bzw. Kartoffelproteine ist.

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Solubility and electrophoretic patterns of heat-denaturated proteins (including samples containing starch) after treatment with SDS (sodiumdodecylsulfat)

Summary The ability of the anionic detergent SDS (sodium-dodecylsulfate) to solubilize native and heat-denaturated proteins of meat and potatoes in presence of disulphide reducing agents was checked by electrophoretic methods. Skeletal muscle proteins of beef, pork, chicken and turkey have shown very similar patterns in SDS-gelelectrophoresis, which could hardly be used for species identification but they are characteristic for fresh or boiled muscles. Proteins of European potato cultivars and primitive cultivars from South America have almost identical SDS-patterns even if taken from boiled potatoes. Their patterns are different from the proteins of other European crops plants and may serve for detection of the presence of potatoes in food mixtures.

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Diese Arbeit ist Teil der Dissertation von I. de Wreede. Die Analyse der tierischen Proteine bearbeitete I. de Wreede.Sonderdruckanfragen an: I. de Wreede (Adresse siehe oben)     

Neue Triterpens?uren der Weintraubenschale

Zusammenfassung Die Cuticula von Traubenschalen enthält neben Oleanolsäure noch 3-Oxo-olean-12-en28-säure, 3-Hydroxi-olean-12-en-28-aldehyd, 3,29-Dihydroxi-olean-12-en-28-säure sowie zwei bisher unbekannte Triterpensäuren. Ihre Strukturen werden durch spektroskopische Daten als 16-Hydroxi-3-oxo-olean-12-en-28-säure und 16-Hydroxi-3-oxo-oleana-1,12-dien-28-säure belegt.

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New triterpenic acids from the peel of grapes

Summary The grape-cuticle contains beside oleanolic acid, 3-oxo-olean-12-en-28-oic acid, 3-hydroxy-olean-12-en-28-aldehyde, 3,29-dihydroxy-olean-12-en-28-oic acid, and two yet hitherto unknown triterpenic acids. Their structures have been elucidated by spectroscopic methods to be l6-hydroxy-3-oxo-olean-12-en-28-oic acid and 16-hydroxy-3-oxo-oleana-1,12-dien-28-oic acid.

     

Assessing exposure to transformation products of soil-applied organic contaminants in surface water: comparison of model predictions and field data

Transformation products (TPs) of chemicals released to soil, for example, pesticides, are regularly detected in surface and groundwater with some TPs even dominating observed pesticide levels. Given the large number of TPs potentially formed in the environment, straightforward prioritization methods based on available data and simple, evaluative models are required to identify TPs with a high aquatic exposure potential. While different such methods exist, none of them has so far been systematically evaluated against field data. Using a dynamic multimedia, multispecies model for TP prioritization, we compared the predicted relative surface water exposure potential of pesticides and their TPs with experimental data for 16 pesticides and 46 TPs measured in a small river draining a Swiss agricultural catchment. Twenty TPs were determined quantitatively using solid-phase extraction liquid chromatography mass spectrometry (SPE-LC-MS/MS), whereas the remaining 26 TPs could only be detected qualitatively because of the lack of analytical reference standards. Accordingly, the two sets of TPs were used for quantitative and qualitative model evaluation, respectively. Quantitative comparison of predicted with measured surface water exposure ratios for 20 pairs of TPs and parent pesticides indicated agreement within a factor of 10, except for chloridazon-desphenyl and chloridazon-methyl-desphenyl. The latter two TPs were found to be present in elevated concentrations during baseflow conditions and in groundwater samples across Switzerland, pointing toward high concentrations in exfiltrating groundwater. A simple leaching relationship was shown to qualitatively agree with the observed baseflow concentrations and to thus be useful in identifying TPs for which the simple prioritization model might underestimate actual surface water concentrations. Application of the model to the 26 qualitatively analyzed TPs showed that most of those TPs categorized as exhibiting a high aquatic exposure potential could be confirmed to be present in the majority of water samples investigated. On the basis of these results, we propose a generally applicable, model-based approach to identify those TPs of soil-applied organic contaminants that exhibit a high aquatic exposure potential to prioritize them for higher-tier, experimental investigations.     

Temporal trends, congener patterns, and sources of octa-, nona-, and decabromodiphenyl ethers (PBDE) and hexabromocyclododecanes (HBCD) in Swiss lake sediments

With the recent ban of pentabromodiphenyl ether (technical PentaBDE) and octabromodiphenyl ether (technical OctaBDE) mixtures in the European Union (EU) and in parts of the United States, decabromodiphenyl ether (technical DecaBDE) remains as the only polybrominated diphenyl ether (PBDE) based flame retardant available, today. The EU risk assessment report for DecaBDE identified a high level of uncertainty associated with the suitability of the current risk assessment approach for secondary poisoning by debromination of DecaBDE to toxic lower brominated diphenylethers. Addressing this still open question, we investigated concentrations and temporal trends of DecaBDE, NonaBDE, and OctaBDE congeners in the sediments of Greifensee, a small lake located in an urban area close to Zürich, Switzerland. PBDE appeared first in sediment layers corresponding to the mid 1970s. While total Tri-HeptaBDE (BDE-28, -47, -99, -100, -153, -154 and -183) concentrations leveled off in the mid 1990s to about 1.6 ng/g dw (dry weight), DecaBDE levels increased steadily to 7.4 ng/g dw in 2001 with a doubling time of 9 years. Hexabromocyclododecanes (HBCD) appeared in Greifensee sediments in the mid 1980s. They are an important class of flame retardants that are being used in increasing amounts, today. As was observed for DecaBDE, HBCD concentrations were continuously increasing to reach 2.5 ng/g dw in 2001. Next to DecaBDE, all 3 NonaBDE congeners (BDE-208, BDE-207, and BDE-206) and at least 7 out of the 12 possible OctaBDE congeners (BDE-202, BDE-201, BDE-197/204, BDE-198/203, BDE-196/200, BDE-205, and BDE-194) were detected in the sediments of Greifensee. Highest concentrations were found in the surface sediments with 7.2, 0.26, 0.14, and 1.6 ng/g dw for Deca-, Nona-, Octa-, and the sum of Tri-HeptaBDE, respectively. While DecaBDE and NonaBDE were found to increase rapidly, the increase of OctaBDE was slower. Congener patterns of Octa- and NonaBDE present in sediments of Greifensee did not change with time. Consequently, there was no evidence for sediment mediated long-term transformation of PBDE within the observed time span of almost 30 years. Despite the high persistence of DecaBDE, environmental debromination occurs, as shown by the detection of a shift in congener patterns of Octa- and NonaBDE in sediments, compared to the respective congener patterns in technical PBDE products. The OctaBDE congener BDE-202 was detected in sediments, representing a transformation product that is not reported in any of the technical PBDE products. Comparison of OctaBDE congener patterns in sediments with OctaBDE congener patterns from known sources reveals that (i) they were distinctively different from the congener patterns in technical PBDE products and (ii) that they were similar to the OctaBDE patterns in house dust and photodegradation products of DecaBDE, suggesting contributions from these sources.     

Enterococci in foods--a conundrum for food safety

Enterococci form part of the lactic acid bacteria (LAB) of importance in foods. They can spoil processed meats but they are on the other hand important for ripening and aroma development of certain traditional cheeses and sausages, especially those produced in the Mediterranean area. Enterococci are also used as human probiotics. However, they are important nosocomial pathogens that cause bacteraemia, endocarditis and other infections. Some strains are resistant to many antibiotics, but antibiotic resistance alone cannot explain the virulence of some of these bacteria. Virulence factors such as adhesins, invasins and haemolysin have been described. The role of enterococci in disease has raised questions on their safety for use in foods or as probiotics. Studies on the incidence of virulence traits among enterococcal strains isolated from food showed that some harbour virulence traits and generally, Enterococcus faecalis harbours more of them than Enterococcus faecium. Regulations in Europe stipulate that safety of probiotic or starter strains is the responsibility of the producer; therefore, each strain intended for such use should be carefully evaluated. For numerous questions, immediate answers are not fully available. It is therefore suggested that when considering an Enterococcus strain for use as a starter or probiotic culture, it is imperative that each particular strain should be carefully evaluated for the presence of all known virulence factors. Ideally, such strains should harbour no virulence determinants and should be sensitive to clinically relevant antibiotics. In general, E. faecium appears to pose a lower risk for use in foods, because these strains generally harbour fewer recognised virulence determinants than E. faecalis. Generally, the incidence of such virulence determinants among E. faecium strains is low, as compared to E. faecalis strains, probably as a result of the presence of pheromone-responsive plasmids.     

Accuracy of continuous ice-core trace-element analysis by inductively coupled plasma sector field mass spectrometry

Trace elements trapped in glaciers are important indicators for the characterization of past biogeochemical cycles, the identification of numerous sources and their varying strength, and thus indirectly provide insight into past climate variations. However, this necessitates highly resolved and continuous records of trace elements in ice. To obtain records corresponding to these requirements, a continuous ice-core melting (CIM) device was coupled to an inductively coupled plasma sector field mass spectrometer (ICP-SFMS). Accuracy of this newly developed method was tested by replicate analysis of longitudinally cut ice-core sections (reproducibility) and by comparing results of the continuous method with the conventional decontamination and analysis procedure. The new, fast method is suited to accurately determine concentrations of a number of elements, such as Li, Na, Mg, Ca, Mn, Co, Br, Sr, Mo, and Tl. However, for 18 elements (including Al and lanthanides) observed concentrations were underestimated when analyzed using the continuous method. Possible explanations of these low concentrations are (i) incomplete dissolution of mineral dust particles contained in the ice resulting from a delayed acidification step and/or (ii) adsorption of dissolved trace elements or mineral dust particles on the surface of the ice melting device.     

Sterol glycosides and cerebrosides accumulate in Pichia pastoris, Rhynchosporium secalis and other fungi under normal conditions or under heat shock and ethanol stress

The occurrence of glycolipids such as sterol glycosides, acylated sterol glycosides, cerebrosides and glycosyldiacylglycerols was examined in the three yeast species Candida albicans, Pichia pastoris and Pichia anomala, as well as in the six fungal species Sordaria macrospora, Pyrenophora teres, Ustilago maydis, Acremonium chrysogenum, Penicillium olsonii and Rhynchosporium secalis. Cerebroside was found in all organisms tested, whereas acylated sterol glycosides and glycosyldiacylglycerols were not found in any organism. Sterol glycosides were detected in P. pastoris strain GS115, U. maydis, S. macrospora and R. secalis. This glycolipid occurred in both yeast and filamentous forms of U. maydis but in neither form of C. albicans. This suggests that sterol glycoside is not correlated with the separately grown dimorphic forms of these organisms. Cerebrosides and sterol glycosides from P. pastoris and R. secalis were purified and characterized by mass spectrometry and nuclear magnetic resonance spectroscopy. The cerebrosides are beta-glucosyl ceramides consisting of a saturated alpha-hydroxy or non-hydroxy fatty acid and a Delta4,8-diunsaturated, C9-methyl-branched sphingobase. Sterol glycoside from P. pastoris was identified as ergosterol-beta-D-glucopyranoside, whereas the sterol glucosides from R. secalis contain two derivatives of ergosterol. The biosynthesis of sterol glucoside in P. pastoris CBS7435 and GS115 depended on the culture conditions. The amount of sterol glucoside in cells grown in complete medium was much lower than in cells from minimal medium and a strong increase in the content of sterol glucoside was observed when cells were subjected to stress conditions such as heat shock or increased ethanol concentrations. From these data we suggest that, in addition to Saccharomyces cerevisiae, new yeast and fungal model organisms should be used to study the physiological functions of glycolipids in eukaryotic cells. This suggestion is based on the ubiquitous and frequent occurrence of cerebrosides and sterol glycosides, both of which are rarely detected in S. cerevisiae. We suggest P. pastoris and two plant pathogenic fungi to be selected for this approach.