Potassium lactate combined with sodium diacetate can inhibit growth of Listeria monocytogenes in vacuum-packed cold-smoked salmon and has no adverse sensory effects

Growth of Listeria monocytogenes in ready-to-eat fish products such as cold-smoked salmon is an important food safety issue. The objective of this study was to evaluate the antilisterial activity of potassium lactate (PL) in combination with sodium acetate (SA) or sodium diacetate (SDA) in cold-smoked salmon and to determine whether these compounds could be incorporated easily into the formulations and technology currently used by processors. A commercial brine injector was used to inject salmon filets with either saturated saline brine or saturated saline brine supplemented with combinations of PL and SA (PURASAL Opti.Form PA 4) or PL and SDA (PURASAL Opti.Form PD 4). In the brine-injected cold-smoked salmon, 2.1% (water phase) PL and 0.12% (water phase) SDA delayed the growth of L. monocytogenes for up to 42 days of vacuum-packaged storage at 10 degrees C. Storage at 25 degrees C for 6 h resulted in only a 1-log CFU/g increase in L. monocytogenes. Treatments with lower concentrations of PL and SDA or similar concentrations of PL and SA resulted in an extended lag phase and slower growth of L. monocytogenes. It was not possible to incorporate more than 2% (water phase) PL while ensuring a minimum of 3% (water phase) NaCl in the finished product because PL decreased the solubility of NaCl. Sensory analyses revealed that the preservatives did not negatively affect flavor or odor. The combination of PL and SDA is therefore a viable technology for preventing L. monocytogenes growth on cold-smoked salmon.     

Block copolymers comprising poly(ethylene oxide) and poly(hydroxyethyl methacrylate) blocks: synthesis and characterization

Monofunctional poly(ethylene oxide) macroinitiators with a molecular weight of 2000, 5000, 10?000, 20?000 and bifunctional poly(ethylene oxide) macroinitiators with a molecular weight of 20?000 were used for the atom transfer radical polymerisation (ATRP) of hydroxyethyl methacrylate (HEMA) in ethylene glycol as a solvent. The polymerisation proceeds in a controlled way up to high conversions. The molecular weight of the obtained copolymers increases linearly with conversion. A high rate of polymerisation was observed for the ATRP of HEMA. The effect of the poly(ethylene oxide) moiety on the course of the reaction is limited to solvating effects. The surface analysis of poly(ethylene oxide)/poly(hydroxyethyl methacrylate) block copolymers by means of atomic force microscopy in tapping mode using phase imaging shows phase separated domains with characteristic features related to the volume fraction of the respective blocks.     

Advanced Alumina Composites Reinforced with Titanium-Based Alloys

New (inter)metallic-ceramic composites for high-temperature structural and functional applications are prepared via high-energy ball milling. During compaction by pressureless sintering, dense Al₂O₃/Ti-based alloy composites are formed that consist of inter-connected networks of the ceramic and the (inter)metallic phases. Ti-Al-V/Al₂O₃ and Ti-Al-Nb/Al₂O₃ composites show enhanced damage tolerance over monolithic Al₂O₃, i.e ., fracture toughnesses up to 5.6 MPa·m^0.5 and bending strengths up to 527 MPa. The resistance against abrasive wear is almost doubled with respect to monolithic Al₂O₃ ceramic. Electrical resistivity scales with the ceramic volume fraction and ranges between 0.3 mΩ·cm and 55.1 mΩ·cm, with only a weak temperature dependence ≤700°C.     

Chemical synthesis of a dual branched malto-decaose: a potential substrate for alpha-amylases

A convergent block strategy for general use in efficient synthesis of complex alpha-(1-->4)- and alpha-(1-->6)-malto-oligosaccharides is demonstrated with the first chemical synthesis of a malto-oligosaccharide, the decasaccharide 6,6'-bis(alpha-maltosyl)-maltohexaose, with two branch points. Using this chemically defined branched oligosaccharide as a substrate, the cleavage pattern of seven different alpha-amylases were investigated. Alpha-amylases from human saliva, porcine pancreas, barley alpha-amylase 2 and recombinant barley alpha-amylase 1 all hydrolysed the decasaccharide selectively. This resulted in a branched hexasaccharide and a branched tetrasaccharide. Alpha-amylases from Asperagillus oryzae, Bacillus licheniformis and Bacillus sp. cleaved the decasaccharide at two distinct sites, either producing two branched pentasaccharides, or a branched hexasaccharide and a branched tetrasaccharide. In addition, the enzymes were tested on the single-branched octasaccharide 6-alpha-maltosyl-maltohexaose, which was prepared from 6,6'-bis(alpha-maltosyl)-maltohexaose by treatment with malt limit dextrinase. A similar cleavage pattern to that found for the corresponding linear malto-oligosaccharide substrate was observed.     

Survival and movement of enterovirus in connection with land disposal of sludges

Coxsackievirus and tritiated water were added to municipal sludges which were placed on lysimeters containing sandy soil or clay soil. It took 23 weeks during a normal Danish winter to inactivate virus from an initial 10⁶tcid₅₀/g sludge to a not demonstrable level. Irrespective of sludge and soil type no virus was demonstrated in the leachate water. The rainfall during December–May was 300 mm.     

Methodology for quantifying the volatile mixing state of an aerosol

Mixing state refers to the relative proportions of chemical species in an aerosol, and the way these species are combined; either as a population where each particle consists of a single species (‘externally mixed’) or where all particles individually consist of two or more species (‘internally mixed’) or the case where some particles are pure and some particles consist of multiple species. The mixing state affects optical and hygroscopic properties, and quantifying it is therefore important for studying an aerosol's climate impact. In this article, we describe a method to quantify the volatile mixing state of an aerosol using a differential mobility analyzer, centrifugal particle mass analyzer, catalytic denuder, and condensation particle counter by measuring the mass distributions of the volatile and non-volatile components of an aerosol and determining how the material is mixed within and between particles as a function of mobility diameter. The method is demonstrated using two aerosol samples from a miniCAST soot generator, one with a high elemental carbon (EC) content, and one with a high organic carbon (OC) content. The measurements are presented in terms of the mass distribution of the volatile and non-volatile material, as well as measures of diversity and mixing state parameter. It was found that the high-EC soot nearly consisted of only pure particles where 86% of the total mass was non-volatile. The high-OC soot consisted of either pure volatile particles or particles that contained a mixture of volatile and non-volatile material where 8% of the total mass was pure volatile particles and 70% was non-volatile material (with the remaining 22% being volatile material condensed on non-volatile particles).

© 2016 American Association for Aerosol Research     

The Diffusible Signal Factor Family of Bacterial Cell?Cell Signals

Bacterial cell-to-cell signals of the diffusible signal factor (DSF) family are cis-2-unsaturated fatty acids that differ in their chain length and branching patterns. Signaling involving DSF family members occurs in diverse bacteria to include plant and human pathogens. In the majority of these organisms, the perception of DSF is linked to turnover of the second messenger cyclic di-GMP by one of two “core” pathways. Additional “accessory” signal transduction pathways can also be found, but are not widely conserved. DSF signaling acts to regulate diverse functions to include biofilm formation and architecture, antibiotic resistance, and the production of virulence factors in pathogens. DSF family signals can also participate in interspecies signaling with other bacteria and interkingdom signaling with the yeast Candida albicans. Such interactions may have importance in modifying microbial behavior during polymicrobial infections.