Characterisation of the spoilage microbiota in raw salmon (Salmo salar) steaks stored under vacuum or modified atmosphere packaging combining conventional methods and PCR-TTGE

In order to characterise the spoilage related to microbiota of raw salmon, a combination of culture-dependent and -independent methods, including PCR–TTGE, was used to analyse 3 raw salmon batches stored for 3 days at chilled temperature in modified atmosphere packaging (MAP) (50% CO₂/50% N₂) or under vacuum. Sensory evaluation, microbiological enumeration and chemical analysis were performed after 3, 7 and 10 days of storage. At the onset of spoilage, 65 bacterial isolates were picked from the plates. Thus, 13 different genera or species were identified by phenotypic and molecular tests: Serratia spp., Photobacterium phosphoreum, Yersinia intermedia, Hafnia alvei, Buttiauxella gaviniae, Pseudomonas sp., Carnobacterium maltaromaticum, Carnobacterium divergens, Lactococcus piscium, Lactobacillus fuchuensis, Vagococcus carniphilus, Leuconostoc gasicomitatum and Brochothrix thermosphacta. The PCR–TTGE profiles and band identification enabled a shift of the dominant populations during the storage to be visualised for all the batches, probably due to the temperature change and the packaging. At the beginning of storage, Pseudomonas sp. dominated the raw salmon microbiota while in the following days (7 and 10), P. phosphoreum and L. piscium were identified as the main bacterial groups. This study enhances the knowledge of MAP and vacuum-packed raw salmon spoilage microbiota.     

Prediction of composition traits of young Charolais bull carcasses using a morphometric method

The relationships among morphological traits and bovine carcass composition traits were analysed in order to select carcass measurements to derive equations for predicting muscle weight, percentage of muscle and muscle to bone ratio. The sample, constituted by 35 young Charolais bulls slaughtered at 18 months old, was homogeneous, e.g. half carcass weight = 225 ± 13.2 kg (standard deviation), carcass fat% = 6.4 ± 1.0, carcass muscle% = 74.58 ± 1.47, carcass bone% = 16.87 ± 0.83. Carcasses were weighed and a sub-group of carcass measurements was selected from the results of a principal component analysis, performed on 76 measurements taken from carcass photographs. The computation of the best combination of variables for prediction was based on the Mallows' Cp statistic and linear regression. The percentage of muscle was best predicted by only three carcass measurements with a relatively low value of fit (R(2) = 0.70). When carcass weight was added to the same measurements to obtain the best prediction for muscle weight, the fit was high (R(2) = 0.98). The prediction of muscle to bone ratio required nine variables and again the fit was high (R(2) = 0.90).     

Isolation and characterization of a psychrotolerant toxin producer, Bacillus weihenstephanensis, in liquid egg products

A psychrotolerant bacteria of the Bacillus cereus group was found responsible for the spoilage of whole liquid egg products. By sequencing a 16S rRNA region and performing a PCR amplification of specific 16S rRNA and cspA signatures, a Bacillus weihenstephanensis was identified. Characterization of this strain shows its ability to grow in defined medium as well as in whole liquid egg at refrigerated temperatures. The strain isolated possesses genes encoding for hemolysin BL, nonhemolytic enterotoxin, and B. cereus enterotoxins and produces enterotoxins with cytotoxic activity in whole liquid egg, even at refrigerated temperatures. The isolate exhibits a clear ability to stick and form biofilms on stainless steel, the most common material used in egg breaking factories, as well as on model hydrophilic (glass) and hydrophobic (polytetrafluoroethylene) materials. These findings show the necessity to monitor for Bacillus contamination in egg products that are often used in the composition of particularly susceptible finished products such as cream, dessert, dairy, meat, and seafood.     

Blind identification of multipath channels: a parametric subspaceapproach

In this paper, blind identification of single-input multiple-output (SIMO) systems using second-order statistics (SOS) only is considered. Using the assumption of a specular multipath channel, we investigate a parametric variant of the so-called subspace method. Nonparametric subspace-based methods require precise estimation of the model order; overestimation of the model order leads to inconsistent channel estimates. We show that the parametric subspace method gives consistent channel estimates when only an upper bound of the channel order is known. A new algorithm, which exploits parametric information on the channel structure, is presented. A statistical performance analysis of the proposed parametric subspace criterion is presented; limited Monte Carlo experiments show that the proposed algorithm is second-order optimal for a large class of channels     

On the stability of periodic orbits in lattice dynamical systems

The variation of the norm of a matrix operator in the space l_q² when q varies is investigated. The linear part of a lattice dynamical system is a matrix operator. The consequences of this variation on the stability of periodic orbits in such systems is given.     

Setting goals to switch between tasks: Effect of cue transparency on children’s cognitive flexibility.

Three experiments examined the difficulty of translating cues into verbal representations of task goals by varying the degree of cue transparency (auditory transparent cues, visual transparent cues, visual arbitrary cues) in the Advanced Dimensional Change Card Sort, which requires switching between color- and shape-sorting rules on the basis of cues. Experiment 1 showed that 5- and 6-year-old children’s performance improved as a function of cue transparency. Experiment 2 yielded the same pattern of results and showed that cue transparency effects cannot be accounted for by cue format only. Finally, Experiment 3 examined the effect of cue transparency in 7- and 9-year-olds and adults. The effect decreased over age for accuracy performance but not for latencies, suggesting that under some conditions, the difficulty of cue translation can still be observed in individuals whose inner speech is efficient. Overall, these findings showed that goal setting substantially contributes to children’s flexible behaviors and continues to influence adults’ performance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Enzymatic Transformations 62. Preparative Scale Synthesis of Enantiopure Glycidyl Acetals using an Aspergillus niger Epoxide Hydrolase‐Catalysed Kinetic Resolution

The hydrolytic kinetic resolution of five glycidaldehyde acetal derivatives was examined using the recombinant Aspergillus niger epoxide hydrolase as biocatalyst. This could successfully be performed, at room temperature, using solely demineralised water as solvent and following a two‐phase methodology allowing us to operate at a global substrate concentration as high as 200 g/L in the reactor. The observed E values were shown to be modest to excellent, depending on the structure of the acetal moiety, indicating that it is possible to achieve this resolution very efficiently just by choosing the right substituents. Both the unreacted (R)‐epoxide and the formed (S)‐diol could thus be obtained in good to excellent ee (ee>99 % for the epoxide). For the best substrates, the reaction could be performed within a few hours by using a biocatalyst over substrate molecular ratio of about 9 to 10×10⁻⁴ mol %. The turnover frequency (TOF) as well as the total turnover number (TON) of the enzyme proved to be excellent as compared to chemical catalysts – reaching respectively values in the order of 6×10² mol sub/mol enz/min and 6×10⁴ mol sub/mol enz. The space‐time yield of the best (two‐phase) reactor could thus reach a value as high as 56 g/L/hour. As a demonstration experiment, a 50‐g scale resolution of glycidaldehyde 2,2‐dimethyltrimethylene acetal was performed.     

A 1D High Performance Thin Layer Chromatography Method Validated to Quantify Phospholipids Including Cardiolipin and Monolysocardiolipin from Biological Samples

The aim of this study is to identify high performance thin layer chromatography (HPTLC) conditions allowing the separation and quantification of mammalian cellular phospholipids (PLs) (sphingomyelin, phosphatidylcholine, phosphatidylserine, phosphatidylinositol, phosphatidylethanolamine, and especially phosphatidic acid, cardiolipin, and monolysocardiolipin, these latter two being specifically located in mitochondria membranes). In order to make this method faster and easier, a 1D HPTLC method is chosen, testing several eluents as well as several staining methods. A pre‐conditioning of HPTLC plates with boric acid and a copper staining reagent followed by carbonization are selected for the quality of PL separation and homogeneity of staining. The selected conditions are discussed and the method validation is performed according to the International Conference on Harmonization guidelines. Linearity is effective between 1 and 8 µg and limit of quantification is between 0.5 and 2.3 µg depending on PL classes. Precision measurements show coefficients of variation <6%, and when amounts are close to the detection limit, <12%. Lipid extracts of tumor cell lines or isolated mitochondria are used to assess PL profiles. This shows that the HPTLC method can be used routinely to follow level variations of PLs. Practical Applications: The changes in PL composition play a crucial role in tumor processes and regulate cellular functions modulating cellular signaling or mitochondrial metabolism. The simple and cost‐effective 1D HPTLC method that is developed is applied to lipid extracts of whole tumor cells or hepatocyte‐isolated mitochondria. It is sensitive as well as precise to detect variations of phosphatidic acid or cardiolipin levels linked to physio‐pathological conditions. It can also be used to investigate the composition changes of other membrane PLs. Moreover, with a simultaneous analysis of 14 samples/standards on the same plate (six plates per day), this method is adapted for large series of samples.