Partial coalescence and whipping capabilities of dairy aerated emulsions as affected by inclusion of monoglycerides with different fatty acid species

Whipping capabilities are the most important indices of dairy aerated emulsions for their use in cakes, desserts and toppings. However, poor whipping capabilities may occur because of included soft fats. Monoglycerides, namely glyceryl monostearate (GMS), glycerol monooleate (GMO) and glycerin monolaurate (GMLa), are the suggested improvers in controlling whipping process through changing partial coalescence behaviours of fat globules. Effects of the three monoglycerides on two crucial whipping factors, that is, fat crystallisation and interfacial properties, were analysed in the present study. It is found that low levels of monoglycerides (<0.25%) showed little effects on the development of partial coalescence, while positive performance was observed in those formulated with increased concentrations ranging from 0.50 to 0.75%. In comparison with GMO, monoglycerides with saturated species significantly improved density and ordering of fat crystal networks and reduced interfacial protein concentrations, contributing to the development of partial coalescence and bubble structures during whipping. Rheology analyses further strongly supported that GMS and GMLa strengthened fat crystal network structure, thereby improving shaping property and heat resistance of foam. The results provided a theoretical basis for improving whipping capabilities of aerated emulsions.     

Effect of Diglycerides on the Crystallisation of Palm Oleins

The crystallisation time of palm olein was found to be rapidly reduced with the addition of palm diglycerides. Of the palm diglycerides, the dipalmitoylglycerol in particular the 1,3-isomer was more effective in causing rapid crystallisation of palm olein. On the other hand, the palmitoyloleoylglycerol appeared to have a retardation effect on the crystallisation time, while the effect from dioleoylglycerol was not very significant. The effects of diglycerides were also discussed in relation to the unsaturation of the olein.     

Polycrystalline silicon thin‐film solar cells on glass by aluminium‐induced crystallisation and subsequent ion‐assisted deposition (ALICIA)

A research project is under way at The University of New South Wales aiming at the realisation of a novel type of polycrystalline silicon thin‐film solar cell on glass. The idea is to first create a thin large‐grained polycrystalline seed layer on glass by aluminium‐induced crystallisation of amorphous silicon and then to epitaxially thicken the seed layer with ion‐assisted deposition. By mid‐2003 this ALICIA project had achieved laboratory cells with voltages of up to 163 mV, as reported elsewhere. In the present paper we give an overview of recent progress (improved Si epitaxy process, improved control of base doping profile due to the use of phosphorus dopants instead of gallium, hydrogen passivation) that has improved the voltages of ALICIA solar cells to 270 mV. Furthermore, the strategy for further voltage improvements is presented. At the present point in time only the voltages of ALICIA cells are known, but obviously solar cells also require current for good efficiency. Hence much improvement in both voltage and current is still needed. Copyright © 2004 John Wiley & Sons, Ltd.     

The Retrogradation of Concentrated Wheat Starch Systems

The ageing of non‐expanded wheat starch extrudates containing 37% and 51% water on a dry solids basis (d.s.b.) at 25°C was studied using Differential Scanning Calorimetry (DSC), Wide Angle X‐ray Diffraction (XRD), proton Nuclear Magnetic Resonance (NMR) relaxometry and Dynamic Mechanical Thermal Analysis (DMTA). The retrogradation rate increased with water content (∼0.02 h⁻¹ at 37% water (d.s.b.) compared to ∼0.06 h⁻¹ at 51%). While a good correlation was found between the DSC, XRD and NMR data, the kinetics of retrogradation measured by DMTA was delayed. The findings were interpreted in terms of the different molecular processes probed by the different techniques. In addition to the kinetics, information on the physical structure of the partially crystalline retrograded materials were obtained. DSC suggested a broad bimodal melting behaviour, which was attributed to the melting of the crystalline structure followed by the dissociation of the double helices. XRD suggested that at both water contents, the recrystallisation of amylopectin led principally to the A‐polymorph. DMTA suggested a significant interaction between the amorphous and crystalline phases, with a requirement of a minimum relative crystallinity index of ∼0.8 (e.g. ∼80% of the crystallinity index of the fully retrograded material), before any increase in the elastic modulus (at 25°C) was measured.     

Effect of OMMT on microstructure,crystallisation and rheological behaviour of UHMWPE/PP nanocomposites under elongation flow

Different loadings of organo-montmorillonite (OMMT) were mixed with ultra-high molecular weight polyethylene (UHMWPE)/polypropylene (70/30) composites under elongation flow. Results showed that ideal dispersion of OMMT nanoparticles could be achieved and most OMMTs intercalated and exfoliated effectively. However, the layer spacing of OMMT decreased with the increase in the content of OMMT. UHMWPE was surrounded by the OMMT layers, and its shape evolved from a compatible phase to a sphere. OMMT caused heterogeneous nucleation in the blends, leading to a high crystallisation temperature. Meanwhile, the intercalated and exfoliated OMMTs promoted the motion of polymer chains, and inhibited the crystallisation process of UHMWPE in the composites. The crystallinity of UHMWPE with 5% OMMT markedly decreased from 48.39% to 41.46%. Various rheological analyses confirmed that the complex viscosity of composites and the storage modulus decreased first and then increased with the increase in the content of OMMT. UHMWPE/PP with 5% OMMT exhibited the ideal mobility.     

The effect of polymers on the crystallisation of n-alkanes from solution,part 1. Preparation and investigation of spin-labelled fumarate–vinyl acetate copolymers

Spin-labelled fumarate-vinyl acetate (FVA) copolymers with octyl (C₈) and octadecyl (C₁₈) ester groups were prepared and characterised. An interaction between the C₁₈FVA and the developing crystals of n-dotriacontane growing from dodecane solution was observed as a slow-motion component in the electron spin resonace (ESR) spectrum of the system. The C₈FVA showed no such behaviour, the spectrum being entirely of the motionally narrowed type through out the crystallisation process. Above the cloud point of the system, no interaction between the polymer and alkane could be detected either in the ESR spectra or from measurements of the rotational correlation times of the spinlabel nitroxide.     

Closed-loop control of crystal shape in cooling crystallization of l-glutamic acid

Recent simulation research has proved the principle that it is possible to exercise closed-loop control over the particle shape of the crystals produced from cooling crystallisation processes through tracking an optimum temperature or supersaturation profile which can be obtained through optimisation using a morphological population balance (M-PB) model. Here, attention is given to experimentally designing a closed-loop control system on a real crystallisation process to produce the desired shape for rod-like crystals. An optimization algorithm was applied to an M-PB model developed for l-glutamic acid crystallisation to find the optimal profiles of cooling temperature and supersaturation that lead to the desired shape of β-form rod-like product crystals. A closed-loop feedback control system was designed to control the solution temperature or concentration to track the optimum trajectory. On a 1-l crystalliser, it was demonstrated that crystals of different shape can be obtained using the developed closed-loop control methodology. Both supersaturation control and temperature control are compared with each other, and also with constant supersaturation strategy in performance in achieving the final product shape.     

Salting‐out crystallisation using NH3 in a laboratory‐scale gas lift reactor

Despite the advantages offered by gas lift reactors with respect to high gas–liquid mass transfer with a low energy input, their acceptance in the crystallisation field has been slow, especially on an industrial scale. Potassium chloride, potassium sulfate, and magnesium chloride hexammoniate (MgCl₂·6NH₃) were crystallised in a laboratory‐scale gas lift crystalliser by salting‐out using ammonia gas. Ammonia mass transfer rates were calculated for each test. To achieve maximum crystal growth, the gas rate in these reactors needs to be optimised for each crystallising system to achieve sufficient gas mass transfer as well as providing sufficient crystal slurry agitation.     

Supercritical antisolvent micronisation of synthetic all‐trans‐β‐carotene with tetrahydrofuran as solvent and carbon dioxide as antisolvent

BACKGROUND: Supercritical antisolvent (SAS) micronisation of synthetic trans ‐β‐carotene was studied using tetrahydrofuran (THF) as solvent and supercritical carbon dioxide (CO₂) as antisolvent, with the objective of increasing its bioavailability and facilitating its dispersion in oil and emulsion formulations as a result of its smaller particle size. The micronised powder was analysed by scanning electron microscopy and high‐performance liquid chromatography. Micronisation experiments were performed in order to evaluate the effects of temperature (308.15–333.15 K), pressure (6.5–13 MPa) and concentration of the liquid solution (6–9 g L^?1). The effect of the supercritical CO₂/THF flow ratio in the range between 4 and 44 (on a mass basis) was also analysed. Determinations of equilibrium concentrations of β‐carotene in the CO₂/THF mixture were also performed. RESULTS: The particle size obtained ranged from 1 to 500 µm, with mean particle diameters around 100 µm. Three types of morphology were found in the precipitated powder: crystalline with superficial pores and leaf‐like appearance; crystalline with regular shapes and blade‐like edges; and crystalline without superficial pores and leaf‐like apearance. The Peng–Robinson equation of state was used to calculate the density of the CO₂/THF binary mixture, and the solubility of β‐carotene in this mixture was correlated with its density. CONCLUSION: The use of the SAS technique to micronise β‐carotene proved to be efficient, and the absence of degradation in the micronised powder allows the industrial application of this technique. Copyright © 2008 Society of Chemical Industry     

Lactose crystallisation in concentrated whey: the influence of vat type

This work aimed to describe the rate of lactose crystallisation in concentrated whey carried out using two different crystallisers, utilising central or lateral stirring. The lactose crystallisation rate differed between treatments, showing high values with use of the central stirrer. Under the experimental conditions, after 4 h of crystallisation, in neither of the vats was 70% lactose crystallisation achieved. With the standardised conditions applied in this study, with soluble solids, time, and stirring and rate cooling being constant, it was possible to verify the influence of the vat type on the rate of lactose crystallisation.