Factors affecting colour and cloud stability in a wildberry herbal drink : a thesis presented in partial fulfilment of the requirements for the degree of M. Tech. in Food Science at Massey University, Albany, New Zealand

An investigation was undertaken into the stability of the natural colour, from anthocyanins, and cloud in a Wildberry Herbal fruit drink. The fruit drinks consisted of cloudy apple and berry fruit juice with natural herb extracts and flavours. The objectives of the research were to identify the cause of cloud instability and sediment formation in the drink; determine the effect of ascorbic acid, berryfruit juice volume, storage temperature and light on anthocyanin stability; investigate the use of stabilisers to prevent sediment formation and determine consumer acceptability of a modified drink. The cause of sediment formation was determined by analysing the contribution of the major ingredients to the total amount of sediment formed. To minimise the sediment, a range of commercially available polysaccharide stabilisers were added to the drink and the amount of sediment formed determined. A consumer sensory evaluation was undertaken to determine consumer acceptability of drinks in which stabilisers had been added to improve the cloud stability. The factors affecting the anthocyanin's in the drink were analysed using a fractional factorial experimental design. The effect of the commercial pasteurisation process on the colour was also investigated. The formation of sediment was identified as being the result of complexing between the unstable cloud of the cloudy apple juice and polyphenolics, including anthocyanins, in the berryfruit juice. No sediment formed during eight weeks storage when clarified apple juice was substituted for cloudy apple juice. The sediment was reduced by approximately 45% using stabiliser systems consisting of either xanthan or a xanthan/propylene glycol alginate mixture. Consumer sensory evaluation of the modified drinks found no significant difference in liking from the standard drink. The anthocyanin loss in the drink was found to be significantly affected by increased storage temperature. Elderberry juice was found to have better colour stability over blackcurrant juice. Pasteurisation did not initially affect the colour stability of the drink. It was recommended that the composition of the Wildberry Herbal drink remain unchanged. The product should be stored at as low a temperature as possible. The drinks should be cooled to ambient temperature as quickly as possible after the pasteurisation process

Critical Casimir Forces and Colloidal Phase Transitions in a Near-Critical Solvent : A Simple Model Reveals a Rich Phase Diagram

From experimental studies it is well-known that colloidal particles suspended in a near-critical binary solvent exhibit interesting aggregation phenomena, often associated with colloidal phase transitions, and assumed to be driven by long-ranged solvent mediated (SM) interactions (critical Casimir forces), set by the (diverging) correlation length of the solvent. We present the first simulation and theoretical study of an explicit model of a ternary mixture that mimics this situation. Both the effective SM pair interactions and the full ternary phase diagram are determined for Brownian discs suspended in an explicit two-dimensional supercritical binary liquid mixture. Gas-liquid and fluid-solid transitions are observed in a region that extends well-away from criticality of the solvent reservoir. We discuss to what extent an effective pair-potential description can account for the phase behavior we observe. Our study provides a fresh perspective on how critical fluctuations of the solvent might influence colloidal self-assembly.Comment: 4 pages, 4 figure

The effects of polydispersity and metastability on crystal growth kinetics

We investigate the effect of metastable gas-liquid (G-L) separation on crystal growth in a system of either monodisperse or slightly size-polydisperse square well particles, using a simulation setup that allows us to focus on the growth of a single crystal. Our system parameters are such that, inside the metastable G-L binodal, a macroscopic layer of the gas phase "coats" the crystal as it grows, consistent with experiment and theoretical free energy considerations. Crucially, the effect of this metastable G-L separation on the crystal growth rate depends qualitatively on whether the system is polydisperse. We measure reduced polydispersity and qualitatively different local size ordering in the crystal relative to the fluid, proposing that the required fractionation is dynamically facilitated by the gas layer. Our results show that polydispersity and metastability, both ubiquitous in soft matter, must be considered in tandem if their dynamical effects are to be understood.Comment: Published in Soft Matter. DOI: 10.1039/C3SM27627

Smart overlay coatings - concept and practice

Smart overlay coatings are a functionally gradient coating system designed to provide high temperature corrosion protection over a wide range of operating conditions. The SMARTCOAT design consists of a MCrAlY base, enriched first in chromium, then aluminium to provide a chemically graded structure. At elevated temperatures, above 900°C (1650°F), the coating oxidises to form a protective alumina scale. However, at lower temperatures this alumina scale does not reform rapidly enough to confer protection under type II hot corrosion conditions. The coating is therefore designed with an intermediate chromium-rich interlayer, which permits the rapid formation of chromia healing areas of type II corrosion damage. Laboratory and burner rig tests have been carried out on a series of developmental smart overlay coatings. These have shown that the development of an intermediate chromium-rich phase provides protection under low temperature hot corrosion conditions, while the aluminium-rich surface layer provides resistance to high temperature oxidation and type I hot corrosion. Thus, the single application of SMARTCOAT permits operation over a broad range of industrial and marine turbine conditio

The Retirement Adjustment Process: Changes in the Well-being of Male Retirees Across Time

The purpose of this prospective study was to (1) evaluate the impact of retirement, (2) monitor the change in adjustment across time, and (3) identify the resources predictive of short- and long-term adjustment in retirement. A sample of 117 male retirees was assessed on indices of physical and psychological health, perceived control, retirement satisfaction, and life satisfaction at 2-4 months preretirement, 1 year post-, and 6-7 years postretirement. The results provided support for a positive impact of retirement, as retirees evidenced increases in well-being during the first year. There was also evidence of a retirement adjustment process, in that aspects of well-being (i.e., psychological health) changed from short- to long-term retirement. Finally, physical health, income, and voluntary retirement status predicted short-term adjustment, while internal locus of control was an additional resource for long-term adjustment. Changes in resources over time also differentially predicted short- and long-term adjustment (e.g., an increase in internal locus of control predicted an increase in activity satisfaction at 1 year but not at 6-7 years postretirement

Gravitational instabilities in a protosolar-like disc - I. Dynamics and chemistry

MGE gratefully acknowledges a studentship from the European Research Council (ERC; project PALs 320620). JDI gratefully acknowledges funding from the European Union FP7-2011 under grant agreement no. 284405. ACB's contribution was supported, in part, by The University of British Columbia and the Canada Research Chairs program. PC and TWH acknowledge the financial support of the European Research Council (ERC; project PALs 320620).To date, most simulations of the chemistry in protoplanetary discs have used 1 + 1D or 2D axisymmetric α-disc models to determine chemical compositions within young systems. This assumption is inappropriate for non-axisymmetric, gravitationally unstable discs, which may be a significant stage in early protoplanetary disc evolution. Using 3D radiative hydrodynamics, we have modelled the physical and chemical evolution of a 0.17 M⊙ self-gravitating disc over a period of 2000 yr. The 0.8 M⊙ central protostar is likely to evolve into a solar-like star, and hence this Class 0 or early Class I young stellar object may be analogous to our early Solar system. Shocks driven by gravitational instabilities enhance the desorption rates, which dominate the changes in gas-phase fractional abundances for most species. We find that at the end of the simulation, a number of species distinctly trace the spiral structure of our relatively low-mass disc, particularly CN. We compare our simulation to that of a more massive disc, and conclude that mass differences between gravitationally unstable discs may not have a strong impact on the chemical composition. We find that over the duration of our simulation, successive shock heating has a permanent effect on the abundances of HNO, CN and NH3, which may have significant implications for both simulations and observations. We also find that HCO+ may be a useful tracer of disc mass. We conclude that gravitational instabilities induced in lower mass discs can significantly, and permanently, affect the chemical evolution, and that observations with high-resolution instruments such as Atacama Large Millimeter/submillimeter Array (ALMA) offer a promising means of characterizing gravitational instabilities in protosolar discs.Publisher PDFPeer reviewe

Orbital-Free Density Functional Theory: Kinetic Potentials and Ab-Initio Local Pseudopotentials

In the density functional (DF) theory of Kohn and Sham, the kinetic energy of the ground state of a system of noninteracting electrons in a general external field is calculated using a set of orbitals. Orbital free methods attempt to calculate this directly from the electron density by approximating the universal but unknown kinetic energy density functional. However simple local approximations are inaccurate and it has proved very difficult to devise generally accurate nonlocal approximations. We focus instead on the kinetic potential, the functional derivative of the kinetic energy DF, which appears in the Euler equation for the electron density. We argue that the kinetic potential is more local and more amenable to simple physically motivated approximations in many relevant cases, and describe two pathways by which the value of the kinetic energy can be efficiently calculated. We propose two nonlocal orbital free kinetic potentials that reduce to known exact forms for both slowly varying and rapidly varying perturbations and also reproduce exact results for the linear response of the density of the homogeneous system to small perturbations. A simple and systematic approach for generating accurate and weak ab-initio local pseudopotentials which produce a smooth slowly varying valence component of the electron density is proposed for use in orbital free DF calculations of molecules and solids. The use of these local pseudopotentials further minimizes the possible errors from the kinetic potentials. Our theory yields results for the total energies and ionization energies of atoms, and for the shell structure in the atomic radial density profiles that are in very good agreement with calculations using the full Kohn-Sham theory.Comment: To be published in Phys. Rev.

Collective traffic-like movement of ants on a trail: dynamical phases and phase transitions

The traffic-like collective movement of ants on a trail can be described by a stochastic cellular automaton model. We have earlier investigated its unusual flow-density relation by using various mean field approximations and computer simulations. In this paper, we study the model following an alternative approach based on the analogy with the zero range process, which is one of the few known exactly solvable stochastic dynamical models. We show that our theory can quantitatively account for the unusual non-monotonic dependence of the average speed of the ants on their density for finite lattices with periodic boundary conditions. Moreover, we argue that the model exhibits a continuous phase transition at the critial density only in a limiting case. Furthermore, we investigate the phase diagram of the model by replacing the periodic boundary conditions by open boundary conditions.Comment: 8 pages, 6 figure