Carl Schaschke

Release cells, breath analysis and in-mouth analysis in flavour research.

The flavour of a food or beverage is not perceived in a single event, but rather as a series of events experienced as the food is consumed. Recent methods in flavour research have taken account of this, and techniques have been developed to study flavour release in model systems (release cells or simulated mouths) and from the mouth or nose of assessors, while consuming foods. However, while there is agreement on the need in some cases for hydration or artificial saliva in simulated mouths, other parameters must be optimised on a case-by-case basis. Individual variability may still be a problem in breath analysis, and further work is required to determine the extent to which there are real differences in volatile profiles. The techniques of release cells and breath analysis must now be applied to provide data, which will allow flavour release to be modelled.

Combined effect of high pressure, temperature and holding time on polyphenoloxidase and peroxidase activity in banana (Musa acuminata)

Polyphenoloxidase and peroxidase enzyme activities were evaluated following combined pressure, temperature and holding time treatment in banana (Musa acuminata). Using pressures of up to 110 MPa, temperatures of up to 70 °C and holding times of up to 25 min, based on a 23 central composite design, the interactive effects were found to significantly influence the activity of both enzymes in prepared banana pulp. Temperature and pressure were found to influence the inactivation of polyphenoloxidase separately, while temperature, pressure and holding time were found to influence the loss of peroxidase in the banana, although no significant interactive effects were found. The reduction in polyphenoloxidase activity was found to be less influenced by the combined treatment than peroxidase activity, thought to be due to solubilisation of the enzyme and effects of the soluble solids content.

Combined Effects of Thermal and Pressure Processing on Food Protein Structure

Food proteins are affected significantly when processed in terms of temperature, holding time and pH. Their combined effects together with temperatures up to 75°C and pressures up to 100 MPa for the three proteins ovalbumin,β-lactoglobulin and lysozyme are reported. The examination of circular dichroism spectra revealed that the secondary and tertiary structure of the three proteins behaved differently when exposed to the processing conditions. β-lactoglobulin was the least stable protein at both pH 7.0 and pH5.6 while lysozyme was the most stable protein being only marginally affected on a secondary structural level at pH 7.0. Although the higher pressures used in this study are recognized as being insufficient to impart the energy necessary to disrupt protein structure, when used in conjunctionwith temperature and holding time, the applied energy was found to be sufficient to disrupt the protein structure. It therefore appears that the processing conditions applied at specific pH act in combination to bring about structural change.

High Pressure Falling Sinker Liquid Viscosity Determination without Supplementary Density Data: A New Approach

Accurate measurement and determination of liquid viscosity data under high pressure conditions requires knowledge of liquid density data. In this study, a high pressure falling sinker-type viscometer was used to determine the viscosity of n-dodecane at elevated pressures up to 132 MPa without supplementary knowledge of liquid density. The viscometer, which involves the downward movement of a cylindrical sinker under the influence of gravity through the liquid contained within a closed tube, avoided the need for density data by repeating the sinker-timing experiments with two geometrically similar but different-sized sinkers thereby allowing the liquid density in the associated formulae to be eliminated. Furthermore, it was possible to subsequently derive liquid density. Both viscosity and density data were compared to published data for which good correlation was found for viscosity. To minimize errors, it is suggested that the two sinkers for such an approach should be of sufficiently differing densities.

Editorial: Biodegradable Materials

This Special Issue “Biodegradable Materials” features research and review papers concerning recent advances on the development, synthesis, testing and characterisation of biomaterials. These biomaterials, derived from natural and renewable sources, offer a potential alternative to existing non-biodegradable materials with application to the food and biomedical industries amongst many others. In this Special Issue, the work is expanded to include the combined use of fillers that can enhance the properties of biomaterials prepared as films. The future application of these biomaterials could have an impact not only at the economic level, but also for the improvement of the environment.

High-pressure viscosity measurement of fatty acids and oils

The viscosities of olive oil and its constituent fatty acids were measured using a falling sinker-type high-pressure viscometer. The viscometer consists of a titanium cylindrical sinker with ferrite core and descends concentrically under the influence of gravity through a close-fitting titanium tube. The movement of the sinker was detected by electrical induction through coils surrounding the tube. For the oil and fatty acids, the calculated dynamic viscosity increased according to the model η=ηo exp (β p). The coefficients were readily obtained by linearizing experimental data for sinker fall-times and found to be dependent on the chain length and degree of saturation.

Prosthetic limb sockets from plant-based composite materials

Background: There is a considerable demand for lower limb prostheses globally due to vascular disease, war, conflict, land mines and natural disasters. Conventional composite materials used for prosthetic limb sockets include acrylic resins, glass and carbon fibres, which produce harmful gasses and dust in their manufacture. Objectives: To investigate the feasibility of using a renewable plant oil-based polycarbonate-polyurethane copolymer resin and plant fibre composite, instead of conventional materials, to improve safety and accessibility of prosthetic limb manufacture. Study Design: Experimental, bench research. Methods: Test pieces of the resin with a range of plant fibres (10.0% by volume) were prepared and tensile strengths were tested. Test sockets of both conventional composite materials and plant resin with plant fibres were constructed and tested to destruction. Results: Combinations of plant resin and either banana or ramie fibres gave high tensile strengths. The conventional composite material socket and plant resin with ramie composite socket failed at a similar loading, exceeding the ISO 10328 standard. Both wall thickness and fibre-matrix adhesion played a significant role in socket strength. Conclusions: From this limited study we conclude that the plant resin and ramie fibre composite socket has the potential to replace the standard layup. Further mechanical and biocompatibility testing as well as a full economic analysis is required. Clinical relevance Using readily sourced and renewable natural fibres and a low-volatile bio-resin has potential to reduce harm to those involved in the manufacture of artificial limb sockets, without compromising socket strength and benefitting clinicians working in poorer countries where safety equipment is scarce. Such composite materials will reduce environmental impact.

Interactive effects of pressure, temperature and time on the molecular structure of ovalbumin, lysozyme and beta-lactoglobulin

The structure of three food proteins, ovalbumin, lysozyme and g -lactoglobulin were investigated when subjected to pressure, temperature and holding time. Structural effects were determined by the examination of circular dichroism spectra. Experiments were performed using pressures of up to 105 MPa, temperatures up to 79 °C and holding times of 30 minutes using experimental design methodology and compared with ultra high pressures (600 MPa). Examination of the spectra showed that the structure of the three proteins behaved differently to the processing conditions. g -lactoglobulin was found to be the least stable protein while lysozyme was the most stable protein. The higher pressure of 105 MPa was not sufficient to cause structural change when used at ambient conditions but when used in conjunction with raised temperatures and holding time, the applied energy was found to be sufficient to disrupt the protein structure.

EXPERIMENTAL VISCOSITY MEASUREMENTS OF BIODIESELS AT HIGH PRESSURE

The viscosity of biodiesels of soybean and rapeseed biodiesels blended with mineral diesel fuel were measured at pressures of up to 200 MPa. Using a falling sinker-type viscometer reproducible viscosity data were obtained based on the time taken for a sinker to descend a fixed distance down an enclosed tube under the influence of gravity. Measurements were taken using pressures which correspond to those of interest in automotive common rail diesel engines, and at temperatures of between 25oC and 80oC. In all cases, the viscosity of the biodiesel blends were found to increase exponentially for which the blends were noted as being more viscous than pure mineral fuels. A pressure-freezing effect was not observed for the blends.