The effect of crowding stress on bacterial growth and sensory properties of chilled Atlantic salmon fillets

Abstract: Atlantic salmon were subjected to minimal preslaughter crowding stress (Control), short‐term crowding for 20 min (SS‐group), or long‐term crowding for 24 h (LS‐group). The fish were filleted prerigor, cut into 270 g pieces, and packaged in modified atmosphere (60% CO₂ and 40% N₂). Fillet quality analyses were determined during 22 d of storage at 0.3 °C. Bacterial growth and unpleasant sensory properties increased earlier in the LS‐group. The negative effects of long‐term preslaughter stress were more pronounced for raw than cooked samples, and more pronounced for odor than flavor. Sequence analyses of bacterial DNA at the end of storage revealed that 100% of the bacteria were comprised by Photobacterium phosphoreum of the SS‐ and LS‐group, whereas the Control group also contained 21% of Carnobacterium maltaromaticum (lactic acid bacteria, LAB). Counting of LAB, using Man‐Rogosa‐Sharke agar, similarly showed higher numbers of the Control group after 15 d of storage. A total bacterial count of log 6 CFU/g was observed after 15 d of storage of the LS‐group, which was 3 and 7 d earlier compared with the Control and SS‐group, respectively. Fillet color, texture, and liquid losses were not negatively affected by preslaughter crowding stress. From the sensory and bacterial analyses, it is concluded that long‐term crowding stress accelerates bacterial growth and development of unpleasant sensory properties, hence reduces the shelf life of prerigor modified atmosphere packaged (MAP) salmon. Practical Application: Stressful handling of Atlantic salmon before slaughter resulted in faster reduction of fresh taste and smell, faster bacterial growth, and hence shorter shelf life. The deteriorative effects were more pronounced of raw compared to cooked salmon. Therefore, salmon should be handled carefully in connection with slaughter to avoid impaired welfare and fillet quality, in particularly for fish that is consumed raw, such as sushi.     

Experimental investigation of an industrial scale black liquor gasifier. 1. The effect of reactor operation parameters on product gas composition

A novel technology to mitigate the climate changes and improve energy security is Pressurized Entrained flow High Temperature Black Liquor Gasification (PEHT-BLG) in combination with an efficient fuel synthesis using the resulting syngas. In order to optimise the technology for use in a pulp and paper mill based biorefinery, it is of great importance to understand how the operational parameters of the gasifier affect the product gas composition. The present paper is based on experiments where gas samples were withdrawn from the hot part of a 3 MW entrained flow pressurized black liquor gasifier of semi industrial scale using a high temperature gas sampling system. Specifically, the influence of process conditions on product gas composition (CO₂, CO, H₂, CH₄, H₂S, and COS) were examined by systematically varying the operational parameters: system pressure, oxygen to black liquor equivalence ratio, black liquor flow rate to pressure ratio and black liquor pre-heat temperature. Due to the harsh environment inside the gasification reactor, gas sampling is a challenging task. However, for the purpose of the current study, a specially designed high temperature gas sampling system was successfully developed and used. The results, obtained from two separate experimental campaigns, show that all of the investigated operational parameters have a significant influence on the product gas composition and present valuable information about to the process characteristics.     

Investigation of particle in-flight characteristics during atmospheric plasma spraying of yttria-stabilized ZrO2: Part 1. Experimental

A detailed investigation of the relationship between the parameters of the spray process and the in-flight properties of the particles was carried out using a multivariate statistical approach. A full factorial designed experiment concerning the spray process was performed, the spray gun parameters’ current, argon flow rate, hydrogen flow rate, and powder feed rate being selected to control the process. The particle properties, viz. velocity, temperature, and diameter, were determined using an optical measurement system, DPV 2000. In addition, the standard deviations of, and the correlations between, the measured particle properties were analyzed. The results showed current to have the strongest impact on particle velocity and particle temperature and argon flow rate to be the only parameter with an inverse effect on velocity and temperature.     

Design of a General‐Purpose European Compound Screening Library for EU‐OPENSCREEN

This work describes a collaborative effort to define and apply a protocol for the rational selection of a general‐purpose screening library, to be used by the screening platforms affiliated with the EU‐OPENSCREEN initiative. It is designed as a standard source of compounds for primary screening against novel biological targets, at the request of research partners. Given the general nature of the potential applications of this compound collection, the focus of the selection strategy lies on ensuring chemical stability, absence of reactive compounds, screening‐compliant physicochemical properties, loose compliance to drug‐likeness criteria (as drug design is a major, but not exclusive application), and maximal diversity/coverage of chemical space, aimed at providing hits for a wide spectrum of drugable targets. Finally, practical availability/cost issues cannot be avoided. The main goal of this publication is to inform potential future users of this library about its conception, sources, and characteristics. The outline of the selection procedure, notably of the filtering rules designed by a large committee of European medicinal chemists and chemoinformaticians, may be of general methodological interest for the screening/medicinal chemistry community. The selection task of 200K molecules out of a pre‐filtered set of 1.4M candidates was shared by five independent European research groups, each picking a subset of 40K compounds according to their own in‐house methodology and expertise. An in‐depth analysis of chemical space coverage of the library serves not only to characterize the collection, but also to compare the various chemoinformatics‐driven selection procedures of maximal diversity sets. Compound selections contributed by various participating groups were mapped onto general‐purpose self‐organizing maps (SOMs) built on the basis of marketed drugs and bioactive reference molecules. In this way, the occupancy of chemical space by the EU‐OPENSCREEN library could be directly compared with distributions of known bioactives of various classes. This mapping highlights the relevance of the selection and shows how the consensus reached by merging the five different 40K selections contributes to achieve this relevance. The approach also allows one to readily identify subsets of target‐ or target‐class‐oriented compounds from the EU‐OPENSCREEN library to suit the needs of the diverse range of potential users. The final EU‐OPENSCREEN library, assembled by merging five independent selections of 40K compounds from various expert groups, represents an excellent example of a Europe‐wide collaborative effort toward the common objective of building best‐in‐class European open screening platforms.     

From Side Chains Rattling on Picoseconds to Ensemble Simulations of Protein Folding

Simulations of biological macromolecules have evolved tremendously since the discoveries of the 1970s. The field has moved from simple simulations in vacuo on picosecond scales to milliseconds of accurate sampling of large proteins, and it has become a standard tool in biochemistry and biophysics, rather than a dedicated theoretical one. This is partly due to increasing computational power, but it would not have been possible without huge research efforts invested in new algorithms and software. Here, we illustrate some of this development, both past and future challenges, and in particular, discuss how the recent introduction of modern ensemble methods is breaking the trend of ever-longer simulations to instead focus on throughput and sampling. This has not only helped simulations become much more accurate, but it provides statistical error estimates, which are critical, as simulations are increasingly used to predict properties that have not yet been measured experimentally.     

Acid Hydrogen Peroxide Treatment of Norway Spruce TMP: The Effect of an Extended pH Range when Catalyzed by Free Ferrous and Free or EDG/EDTA-Chelated Ferric Ions

The influence of different types of iron salts (i.e., ferrous or ferric cations with sulphate, nitrate or chloride anions) on the reaction between coarse thermomechanical pulp and acid hydrogen peroxide (Fenton chemistry) was studied when the initial pH was 3.2 and 5.3. Also, ferric ions chelated with EDTA or EDG at different molar ratios were compared with ferrous sulphate when the initial pH was extended from about 3 to 8. Different anions of ferric ion salt gave a similar catalytic effect. At an initial pH of 7–8, the ferric-EDTA catalyzed reaction resulted in similar or higher hydrogen peroxide consumption and more detectable hydroxyl radicals than the ferrous sulphate catalyzed reaction, but less reaction with the pulp was indicated. Between pH 5–8, using Fe-EDG as a catalyst gave higher hydrogen peroxide consumption and more detectable hydroxyl radicals than if using ferrous sulphate; however, the measured effect on the pulp was similar or less.     

Using a GIS system in mapping risks of nitrate leaching and erosion on the basis of SOIL/SOIL-N and USLE simulations

An assessment system that combines digital information on soil types, climates, slopes and crops with simulated values of nitrate leaching and erosion within a geographical information system was developed. The system was used for assessing risks of nitrate leaching and erosion on the regional as well as national scale, having municipalities as the level of aggregation. In Denmark the system has been used for assessing risks of erosion at a catchment scale.     

Mechanism and kinetics of the free radical ring-opening polymerization of cyclic allylic sulfide lactones

The polymerization of 7-, 8- and 11-membered lactones, 6-methylene-1,4-oxathiepan-7-one, 3-methylene-1,5-oxathiocan-2-one and 3-methylene-1-oxa-5-thiacycloundecan-2-one in benzene at 70, 40–70 and 40–65 °C, respectively, is presented. All polymerizations proceeded with complete ring-opening up to approximately 25% conversion, where insoluble polymer was formed. Evidence is given attributing polymer double bond loss to crosslinking, although redistribution of the molecular weights via addition to polymer double bonds followed by β-fragmentation also appears to occur for polymerizations of the 8- and 11-membered lactones. Michael adducts of lactones with 2-methyl-2-propanethiol were prepared as models for chain-transfer products of hydrogen abstraction by carbon-centred radicals. Polymerization rates were found to increase marginally with ring size. Arrhenius parameters obtained for the polymerizations of the 8- and 11-membered lactones indicated that the addition step was more important than fragmentation in determining the rate of propagation.     

Aflatoxin contamination of consumer milk caused by contaminated rice by‐products in compound cattle feed

BACKGROUND: Elevated levels of aflatoxin M1 were observed in routine checks of consumer milk in southern Sweden in early 2006. A trace‐back study revealed contaminated milk from several farms, and a total of 68 farms were banned from delivering milk to dairies for shorter or longer periods. The maximum level of aflatoxin M1 in a single sample from an individual farm was 257 ng kg^?1 fresh milk. RESULTS: Aflatoxin analyses of commercial compound feed revealed that the contamination originated from the ingredient rice feed meal, a by‐product from the preparation of Basmati rice for human consumption. Up to 56 µg kg^?1 of aflatoxin B1 was found in rice feed meal at one feed mill. CONCLUSION: The present example shows that an aflatoxin‐contaminated minor feed ingredient included at less than 10% (w/w) of compound cattle feed can significantly contaminate the milk produced. This emphasises the need for effective monitoring of the feed chain of food‐producing animals in order to prevent food contamination. Copyright © 2008 Society of Chemical Industry