Adsorption of hydrophobin/ß-casein mixtures at the solid-liquid interface.

The adsorption behaviour of mixtures of the proteins ß-casein and hydrophobin at the hydrophilic solid-liquid surface have been studied by neutron reflectivity. The results of measurements from sequential adsorption and co-adsorption from solution are contrasted. The adsorption properties of protein mixtures are important for a wide range of applications. Because of competing factors the adsorption behaviour of protein mixtures at interfaces is often difficult to predict. This is particularly true for mixtures containing hydrophobin as hydrophobin possesses some unusual surface properties. At ß-casein concentrations ⩾0.1wt% ß-casein largely displaces a pre-adsorbed layer of hydrophobin at the interface, similar to that observed in hydrophobin-surfactant mixtures. In the composition and concentration range studied here for the co-adsorption of ß-casein-hydrophobin mixtures the adsorption is dominated by the ß-casein adsorption. The results provide an important insight into how the competitive adsorption in protein mixtures of hydrophobin and ß-casein can impact upon the modification of solid surface properties and the potential for a wide range of colloid stabilisation applications.

Effect of molecular structure of phenolic families as hydroxycinnamic acids and catechins on their antioxidant effectiveness in minced fish muscle.

The antioxidant effectiveness of two different families of phenolic compounds, hydroxycinnamic acids and catechins, added as a power (0.001% w/w) to chilled minced horse mackerel muscle was evaluated. Caffeic acid, chlorogenic acid, o-coumaric acid, and ferulic acid were selected as hydroxycinnamic acids with similar molecular structures. Commercial catechins with different numbers of hydroxylic groups, including catechin, gallocatechin, catechin gallate, and gallocatechin gallate, were also tested. The effectiveness found was individually discussed for each family as a function of the molecular structure. The capacity of hydroxycinnamic acids for donating electrons seems to play the most significant role for retarding the development of rancidity in fish muscle. Conversely, the properties related to the ability for chelating metals and the distribution between oily and aqueous phases were not correlated with the inhibitory activities. Among hydroxycinnamic acids, the results highlighted the potent antioxidant activity of 10 ppm caffeic acid in inhibiting lipid oxidation in fish muscle. Its antioxidant efficacy was similar to that of propyl gallate. Among catechins, catechin showed the highest antioxidant activity. There was an increment of efficacy in fish muscle using concentrations ranging between 10 and 100 ppm of both caffeic acid and catechin.

Detection of benzene and other gases with an open-path, static Fourier-transform UV spectrometer.

Releases of benzene and other gases have been detected and quantified using a novel optical, open-path instrument based on a deuterium light source and a static Fourier-transform spectrometer. The spectrometer uses Wollaston prisms to form an interferogram in the spatial domain that is recorded by use of a detector array. The instrument is designed to operate in the ultraviolet region of the spectrum between 200 and 270 nm, which coincides with strong absorption features in the spectra of many gases of environmental and health interest. Using the instrument with a 5-s measurement period provides a path-integrated concentration sensitivity to benzene of 2 parts in 10(6) times meter, which corresponds to a 20-parts in 10(9) detection limit over a typical path length of 100 m.

Thermal inactivation of Listeria monocytogenes studied by differential scanning calorimetry.

The effect of NaCl on the thermal inactivation of Listeria monocytogenes has been investigated by conventional microbiological techniques and by using differential scanning calorimetry (DSC). Addition of 1.5 M-NaCl to cells grown at lower NaCl concentrations significantly increases the tolerance of cells to mild heat stress (56-62 degrees C). DSC thermograms show five main peaks which are shifted to higher temperatures in the presence of 1.5 M-NaCl. Measurement of loss of viability in the calorimeter gave good correlation between cell death and the first major thermogram peak at two NaCl concentrations. The time course of the loss of this first peak when cells were heated and held at 60 degrees C in the calorimeter matched the loss of viability, whereas the peak attributable to DNA showed little change during this process. The use of DSC to investigate the mechanisms involved in thermal inactivation is discussed.

The role of the endomysium in the salt-induced swelling of muscle fibres.

Variable uptake of water is a persistent problem in meat processing. To try to understand the changes that occur during water uptake, and thereby explain this variability, we have measured the swelling of salt-treated single muscle fibres from rabbit longissimus dorsi. By dissolving out the myofibrillar proteins with SDS we have been able to tell whether or not a dissected fibre has an endomysial connective sheath. We find that some fibres do lack a sheath and that these stripped fibres swell on average approximately five times more than intact fibres in 0·25 m KI. This shows that the endomysium limits the swelling of the fibre in salt, as is also shown by the greater swelling of those parts of fibres from which the endomysium has been deliberately removed. On prolonged immersion in 0·25 m KI the stripped parts of fibres shrink after swelling whereas the smaller swelling of unstripped parts is maintained. With careful, slow dissection, the proportion of stripped fibres is low at all times post mortem, but if a quicker method is used, the proportion of stripped fibres increases with time post mortem. As ageing proceeds, an increasing incidence of transverse fractures reduces the productivity of the quicker method, so the slow method has to be used. Regardless of the method of dissection the swelling of stripped and unstripped fibres does not depend on time post mortem. Thus it is the changing proportion of stripped fibres that underlies the earlier report (Wilding et al. Meat Sci., 1986 18, 55) of a dependence of swelling on time post mortem. The ease of stripping of endomysium from muscle fibres may be important in meat processing. Thus whether or not fibres produced during comminution and mixing of meat are stripped directly affects water uptake. The extraction of myofibrillar proteins may also be affected, which would be important for the adhesion of cooked reformed meat products.

Salt-induced swelling of meat: The effect of storage time, pH, ion-type and concentration.

The effect of hypertonic salt solutions on meat fibres has been studied as a function of post-mortem storage. Rabbit longissimus dorsi fibres (after about 20 h post-mortem storage at 4°C), were found to swell in hypertonic salt solutions, such as 0·25m KI or 0·6m KCl, to two to three times their original diameter. This swelling occurred in the fibre transverse plane only. X-ray diffraction shows swelling occurs by a combination of an increase in the myofilament lattice spacing and a loss of myofilament order. Fibre swelling is highly co-operative. At pHs below the isoelectric point of the myofibrillar proteins, hypertonic salt solutions induce fibre shrinkage. The post-mortem time course of response shows a peak at 18-35 h bounded by periods of minimal or zero response. We propose that the collagenous endomysial sheath acts as a restraint to myofibril swelling and that the characteristics of post-mortem swelling are a balance of the myofibrillar propensity to swell and the constraint of the endomysium.

Who does what? Role definition in a psychiatric hospital.

This is a report of an interdisciplinary workshop which was held to define the roles of different disciplines within a psychiatric unit. While the report emphasizes the medicolegal responsibility of the psychiatrists, we found, in a review of the knowledge background of the several disciplines, potentials for a further utilization of the knowledge which is acquired during their training. Meeting the patient's needs is the prime factor in determining the roles of the disciplines. The needs of the patient have expanded. Each discipline has both an exclusive role and an inclusive role. One important result of the workshop was the warmth and the esprit de corps that was felt afterwards.