Parallel enzymatic and non-enzymatic formation of zinc protoporphyrin IX in pork

Zinc protoporphyrin is formed in pork homogenates in both enzymatic and non-enzymatic reactions. Ferrochelatase is active in formation of the highly fluorescent pigment known from Parma ham as demonstrated by inhibition with N-methylmesoporphyrin and by thermal inactivation. A non-enzymatic transmetallisation reaction, exchange of iron in myoglobin by zinc(II), is demonstrated by Pb(II) inhibition of zinc protoporphyrin formation at low Pb(II) concentrations, but promoted at higher Pb(II) concentrations. The non-enzymatic reaction is characterised as a slow bimolecular reaction between protoporphyrin IX and zinc(II) with a second-order rate constant of 0.63 l mol⁻¹ s⁻¹ at 35 °C and a high energy of activation of 98 kJ mol⁻¹ for acetone:water (3:1, v/v) as solvent. Zinc protoporphyrin formation is concluded to be thermodynamically controlled with a formation constant of 4 × 10⁵ M (35 °C, acetone:water (3:1)). An efficient inhibition of formation of zinc protoporphyrin by nitrite is related to myoglobin as substrate and involves both enzymatic and non-enzymatic reactions.     

Spatial distribution of light-induced lipid oxidation in semi-hard yellow cheese as detected by confocal microscopy

The migration of oxidative damage in semi-hard yellow cheese resulting from surface exposure to 436 nm monochromatic light with an intensity of 2.5 × 10¹⁷ quanta min⁻¹ cm⁻² for 0, 5, 10, and 15 min was followed by confocal laser scanning microscopy using labelling with the lipophilic fluorescence ratio probe C₁₁-Bodipy (581/591). From 5 × 5 × 5 mm cubes of cheese exposed to light on one plane 35 μm was sliced off and fluorescence of oxidised and non-oxidised probe recorded simultaneously on the surface of the slice reaching 250 μm inwards from the exposed surface. From the emission of the fluorescence ratio probe light-induced lipid oxidation could be followed with time of exposure to light. The penetration of light inwards in the cheese with time expressed as quanta cm⁻², as calculated from light transmittance at 436 nm determined spectrophotometrically for cheese slices of up to 300 μm thickness, together with light intensity as determined by actinometry, could alone account for the inwards migration of oxidation. Diffusion of radicals seems of less importance for spatial dispersion of light-induced oxidation in semi-hard cheese.     

By-products from herbs essential oil production as ingredient in marinade for turkey thighs

Herb decoctions—the aqueous extract of rosemary, sage and thyme, left as by-product after steam distillation of essential oils, were investigated as a source of antioxidants in marinades for turkey thigh meat. Lipid oxidation after marinating, cooking and chill storage (warmed over flavour, WOF) was assessed by thiobarbituric acid-reactive substances (TBARS), GC-MS and sensory judgement on marinated and untreated meat. Results showed that marinating with herb decoctions, which exerted antioxidant activity (free radical scavenging), was an effective means of retarding lipid oxidation in raw and cooked meat. Meat from the rosemary marinade had the lowest TBARS values and volatile levels, while the control samples showed the highest values throughout the marinating, cooking and storage period. Oxidative changes in meat marinated with thyme and sage were significantly more advanced than in meat marinated with rosemary decoction. The partial least squares regression (PLS-R) showed that control samples were strongly related to the oxidation variables (volatiles, TBARS, rancidity) while the marinated meat had high scores for spicy and acidic odour and flavour. Results indicated that antioxidants contained in herb decoction, could be exploited in marinades to prevent rancidity in stored, heat-treated turkey meat products.     

Modelling the coupled transfer of mass and thermal energy in the vapour–liquid region of a nitrogen–oxygen mixture

Current non-equilibrium distillation models do not explicitly include the coupling between thermal and mass fluxes. We present a calculation model for the coupled transfer of mass and thermal energy in the vapour–liquid region of a binary mixture. The region is modelled as a vapour–liquid interface in between two homogeneous films. The entropy production in the vapour–liquid region can be calculated using both irreversible thermodynamics and the entropy balance. The film thickness ratio is found by requiring the entropy production calculated with the two methods to be equal, while keeping the vapour film thickness fixed. Using a nitrogen–oxygen mixture as example, we show that neglecting the coupling between thermal and mass fluxes can have a large impact on the magnitude and direction of the theoretical (net) fluxes. The size of the impact depends on the vapour film thickness, but it is significant for all thicknesses. By increasing the number of control volumes that is used to represent the liquid and vapour films, we also show that the fluxes depend highly on the resistivity profiles in the films. They depend slightly on the interface resistance. A sensitivity analysis of the transport properties shows that accurate values of the Maxwell–Stefan diffusion coefficients in both homogeneous phases and of the liquid phase heat of transfer are most important. Especially the measurable heat flux at the liquid boundary of the system is sensitive to neglect of coupling, to neglect of the interface resistance and to uncertainties in the transfer properties.     

Modeling a non-equilibrium distillation stage using irreversible thermodynamics

We compare transport equations derived from non-equilibrium thermodynamics to a classical rate model developed over the last 20 years, in terms of their ability to calculate the heat and mass fluxes by modeling a segment of a packed distillation column. We show, using water and ethanol separation as an example, that there is a significant coupling between heat and mass transfer. Neglect of this transport coefficient leads to variations in the magnitude, even the sign of the calculated heat flux, while the mass flux is less affected.     

ICT and Integrated Care: Some Dilemmas of Standardising Inter-Organisational Communication

There is a growing interest in the issues of how to organise healthcare work along individual patient cases rather than along the demarcation lines of healthcare organisations. Health information systems, such as electronic patient records, are seen as important change agents, since they are asserted to help the coordination of care across organisations through fast and accurate exchange of clinical data. The paper explores how a semi-standardised discharge letter is employed to communicate about the patient between two organisational settings, the hospital and the general practitioner. It is shown that the discharge letter plays a double role as informational tool and accounting device. And it is argued that further standardisation of the discharge letter content – in order to facilitate electronic exchange – is likely to strengthen the letters role as a tool for organisational accountability and weaken it as a clinical tool. The paper concludes that this finding adds to the theoretical understanding of how computers support cooperative work, and that understanding how healthcare professionals present themselves as accountable and trustworthy should be of major concern when designing healthcare ICTs.     

Study of Cheese Associated Lactic Acid Bacteria Under Carbohydrate-Limited Conditions Using D-Stat Cultivation

The metabolic pathways alternative to glycolytic energy (ATP) during growth of starter and nonstarter lactic acid bacteria were studied simulating the depletion of carbohydrates during cheese ripening. D-stat cultivation strategy with the gradual decrease of galactose concentration in tryptone-arginine feeding medium was used. With the decrease of galactose feeding, the biomass yield calculated on carbohydrate consumption (Y_X/HEX) and acetate/lactate production ratio of all strains increased. We assume that ATP and biomass yields improved by directing the pyruvate flow from lactate to acetate and that metabolic energy could be obtained either by producing acetate from carbohydrates or from arginine metabolism in ADI-positive strains. Four LAB strains out of eight produced ornithine from arginine indicating active arginine-deiminase (ADI) pathway. These ADI-positive strains achieved 3-10 times higher Y_X/HEX than ADI-negative strains in tryptone-arginine medium. Lactobacillus plantarum also used serine as an energy source. Starters and NSLAB strains using the amino acids arginine and serine or limited amounts of carbohydrates therefore have the potential to influence flavor production in cheese more efficiently.     

Oxy-fluoro aluminate complexes in molten cryolite melts

Cryoscopic measurements on the KF rich side in the reciprocal salt system KF-AlF₃-K₂O-Al₂O₃ are presented. The amounts of K₃ AlF₆ and K₂O added to KF are so small that ideal Henrian behaviour of the solution can be expected. The results which indicate complex formations with the Al₂OF_2x^4?2x complex as the dominating species for atomic ratio O/Al < 0.3 and a mol fraction of K₃AlF₆ < 0.05, agree with similar investigations of the corresponding sodium system. A new possible explanation of the anode effect in the industrial aluminium electrolysis is given.     

Ex situ measurements of through-plane thermal conductivities in a polymer electrolyte fuel cell

In this paper thermal properties for materials typically used in the proton exchange membrane fuel cell (PEMFC) are reported. Thermal conductivities of Nafion membranes were measured ex situ at 20 °C to be 0.177 ± 0.008 and 0.254 ± 0.016 W K⁻¹ m⁻¹ for dry and maximally wetted membranes respectively. This paper also presents a methodology to determine the thermal conductivity of compressible materials as a function of applied load. This technique was used to measure the thermal conductivity of an uncoated SolviCore porous transport layer (PTL) at various compaction pressures. For the dry PTL at 4.6, 9.3 and 13.9 bar compaction pressures, the thermal conductivity was found to be 0.27, 0.36 and 0.40 W K⁻¹ m⁻¹ respectively and the thermal contact resistivity to the apparatus was determined to be 2.1, 1.8 and 1.1 × 10⁻⁴ m² K W⁻¹, respectively. It was shown that the thermal contact resistance between two PTLs is negligible compared to the apparatus’ thermal contact resistivity. For a humidified PTL, the thermal conductivity increases by up to 70% due to a residual liquid saturation of 25%.     

Application of chemometrics to low-field 1H NMR relaxation data of intact fish flesh

The possibilities for application of low-field ¹H nuclear magnetic resonance (NMR) as a rapid method for simultaneous assessment of basic quality parameters in fish were explored. In a first experiment, 200 salmon (Salmo salar) samples mapping the variation over an entire fish were measured by NMR and subsequently analysed for oil or water content by standard chemical methods. In a second experiment, 58 differently thawed cod (Gadus morhua) samples were measured by NMR and subsequently analysed for water-holding capacity. Correlations between chemical data and NMR data were evaluated using partial least squares (PLS) regression on complete relaxation curves and compared with conventional regression models on exponential fitting parameters. Predictions on an independent test set were superior for the PLS regression models, with optimal prediction errors of 12 g kg⁻¹, 6 g kg⁻¹ and 3.9% for oil and water content in fresh salmon flesh and water-holding capacity in thawed cod flesh respectively. Thus rapid, non-invasive low-field NMR can be used to simultaneously determine both oil and water content of fish flesh. Furthermore, it can predict water-holding capacity of cod flesh, with an R² of 0.9 over the range 30–90%, as determined by a centrifuge test. © 1999 Society of Chemical Industry