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    Effect of bound ligands and [kappa]-casein on the denaturation of [beta]-lactoglobulin : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology at Massey University
    (Massey University, 2000) Cho, Younghee
    The objective of this study was to gain greater understanding of the behaviour of bovine β-lactoglobulin (β-lg) during thermal denaturation. The first part of the study was focused on gaining more knowledge of the structural changes in β-lg during heat-induced and urea-induced denaturation and the effect of ligands and the genetic variants of β-lg. The second part of the study explored the mechanism of the heat-induced interaction of β-lg with κ-casein (κ-CN) and the effects of genetic variants. The reversible early steps during thermal denaturation of β-lg are not readily separated from the later irreversible steps which involve sulphydryl-disulphide interchange reactions. However, it should be possible to examine the behaviour of β-lg in the early steps without reactive thiols either by using a porcine β-lg, that does not have cysteine residue equivalent to Cys-121 of bovine β-lg, by blocking the free thiol or by using solvent denaturation. Heating to 80 °C irreversibly altered near- and far-UV circular dichroism (CD) spectra, and 1,8-anilinonaphthalene sulphonate and retinol binding fluorescence spectra for bovine β-lg, but not for porcine β-lg which unfolded reversibly. Also the examination of the induced CD spectral changes of retinol and cis-parinaric acid (PnA) on binding to bovine β-lg B upon heating revealed that bovine β-lg lost the ability to bind retinol and PnA in a chiral environment. In contrast, porcine β-lg did not show significantly induced CD bands upon mixing with retinol, but PnA/β-lg mixtures showed induced CD bands of low intensity. In addition to the lack of a free thiol group in porcine β-lg, the sequence differences between bovine β-lg and porcine β-lg are also likely to affect the behaviour of these β-lgs during heat treatment and the binding of ligands. Although palmitic acid does not show any absorbance in CD spectra, it enhanced the stability of the bovine β-lg and porcine β-lg mixture. The urea-induced unfolding of bovine β-lg at neutral pH (6.7) revealed that the stability of the genetic variants followed the order, β-lg B<β-lg A<β-lg C, as observed during thermal denaturation and tryptic hydrolysis. The stabilisation effect was also observed by adding retinol, retinoic acid and palmitic acid during urea denaturation of β-lg, and by retinol, retinyl acetate and PnA during ammonium sulphate denatuation of β-lg. Blocking the sulphydryl group of β-lg destabilised the native protein against urea denaturation through the introduction of a bulky group to the compact structure of β-lg. This result, together with the results for porcine β-lg, confirms that the sulphydryl group plays an important role in the unfolding of bovine β-lg. In the second part of the study, an attempt was made to investigate the effect of bovine κ-CN on the established heat-induced unfolding and aggregation pathway of bovine β-lg, by adding κ-CN A or κ-CN B to native or pre-heated β-lg A, B or C and heating the mixture. The CD band intensity of the mixture of β-lg and κ-CN at 270 nm, an index of significant alteration to the disulphide bond dihedral angle, indicated increasing structural changes involving disulphide bonds during heat treatment. The rates of loss of β-lg and the distributions of intermediate products were determined using alkaline- and sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). During reaction with β-lg, some monomeric κ-CN was found by SDS-PAGE, probably as a result of disulphide bond interchanges between κ-CN and β-lg, and two-dimensional PAGE also revealed disulphide-bonded β-lg/κ-CN aggregates. In the presence of κ-CN, the loss of monomeric β-lg increased and less non-native monomer and dimer were observed compared to β-lg alone and κ-CN reacted more rapidly with β-lg that had been unfolded by prior heat treatment than with native β-lg. This suggested that β-lg probably denatured (unfolded) independently and either simultaneously or consequently and contained higher sulphydryl reactivity than native β-lg, which lead to the reactions with κ-CN via disulphide bond interchange. It is possible that the equilibrium between native β-lg and denatured β-lg shifted rapidly, because κ-CN preferred to interact with denatured (unfolded) β-lg that has higher sulphydryl reactivity than native β-lg. The kinetics of the interaction between β-lg and κ-CN were evaluated from the heat-induced loss of alkaline-monomeric β-lg at 80 °C. The interaction between β-lg and κ-CN could not be described by any reaction order between 1.0 and 2.0. The slopes of the plots changed at about 7.5-10 min heating time and this corresponded to intensity changes in the alkaline-monomeric, non-native monomeric and dimeric β-lg bands, which increased during the first 10 min of heating and then slightly decreased or remained relatively constant for the rest of the heating. The loss of native β-lg in β-lg/κ-CN mixtures during heating at 80 °C was shown to be significantly influenced by the genotypes of both β-lg and κ-CN. The κ-CN B variant showed considerably higher reactivity than κ-CN A, while the β-lg B variant was the most reactive. The greatest loss of native β-lg was observed from the β-lg B/κ-CN B mixture
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    Technical information capture for food product innovation in Thailand : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology at Massey University in Food Technology at Massey University, Palmerston North, New Zealand
    (Massey University, 2001) Prasong Siriwongwilaichat
    Since rapidly effective product design and launch requires advanced technical skills and as new knowledge is expanding at an exponential rate, it is critical that food technologists keep up to date with international scientific developments. This is significant in Thailand in which the food market has been developed as a result of greater industrialisation, changes in consumer lifestyle and higher demand for processed foods. This study has identified the main technical knowledge sources used by Thai food manufacturing companies to support their development of new branded food products. Data were obtained from interviews with sixty two food processing companies, forty three potential providers of technical information and services, and from three focus groups held with technical food product developers. Internal technical staff in the food manufacturing companies were the major source of technical knowledge for food product development. Food ingredient suppliers were the most important outside providers of knowledge to these technical staff. The main technical information and services provided by the food ingredient suppliers included ingredient specifications, food recipes, consultancy, and product testing. Technical information was mostly required to support product formulations, food processing, shelf life studies, and quality control. New products that were radically innovative required more external technical knowledge sources, usually equipment suppliers, than those that were incrementally innovative. The main barriers to technical knowledge absorption were foreign language difficulties, time limitation and business secrecy. To strengthen food product development activities in Thailand, it is recommended that a company enhance internal technical staff's capabilities to absorb external technical knowledge more efficiently. In addition, the technical knowledge providers should also simplify technical information access to the food companies.
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    Image processing and DSP technology applied to remote activity monitoring : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Technology at Massey University
    (Massey University, 2000) Body, Nick
    This thesis describes the development of image processing algorithms to achieve industrial remote activity monitoring. The design of such algorithms is constrained by the requirement that they must be implemented in real-time on a cost effective digital signal processor (DSP). A review of the literature revealed that two viable alternatives were available. These are JPEG, a well established lossy block-based image compression algorithm and methods using wavelets. A suitable family of wavelets was identified as the biorthogonal-7.9, the coefficients indicating the number of taps in the quadrature mirror filters at the heart of the transform. Data compression is then achieved through the construction of zerotrees followed by sequential baseline coding. The two candidate algorithms were then systematically compared for recovered image quality and implementation cost at high compression ratios in the range of 16:1 to 64:1. On this basis the wavelet approach was selected and its implementation on a DSP studied. The architectural features of the Motorola 56303 DSP are presented and analysed. It is shown that the various components required for the wavelet based algorithm can be efficiently mapped onto the DSP architecture. Motion detection and image watermarking algorithms were designed and co-operatively implemented with the compression algorithm. A new method of watermarking highly compressed images was developed and this algorithm has been named the Image Authentication Watermark. A new way of representing optimal Huffman code tables has been developed to enable Huffman entropy coding to perform competitively with the more complex arithmetic coding. A product of this research is a smart digital camera that has been integrated into an automated video surveillance system now in industrial production.
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    Studies into the hydraulics of waste stabilisation ponds : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Environmental Engineering at Massey University, Turitea Campus, Palmerston North, New Zealand
    (Massey University, 2001) Shilton, Andy
    Wastewater stabilisation ponds are used extensively to provide wastewater treatment throughout the world. A review of the literature indicated that, while understanding the hydraulics of waste stabilisation ponds is critical to their optimisation, the research in this area has been relatively limited and that there is a poor mechanistic understanding of the flow behaviour that exists within these systems. Traditional tracer studies were used in this study but, in addition, new methodologies were developed involving drogue-tracking techniques to directly quantify the internal flow pattern. The investigation included study of physical scale models in the laboratory, operational ponds in the field and the simulation of both using computational fluid dynamics (CFD) mathematical modelling. Twenty experimental configurations were tested in the laboratory with the variables being: retention time; outlet position; inlet type and position; and the influence of a baffle. Ten of these experimental cases were then mathematically modelled and, in general, the simulations had close similarity to the experimental data. In the next phase of the work, the tracer and drogue tracking techniques were applied on two full-scale waste stabilisation ponds in the field. For one of the ponds a large scale model was also constructed. Mathematical modelling was again performed and a high degree of similarity was achieved. The study then finished with a broad review of wind effects and an investigation of integrating a biodegradation equation within the CFD model. While it was concluded that a CFD model cannot always be expected to precisely predict the performance of a field pond, this work has validated its use to the extent that it can be pragmatically applied for the systematic evaluation of alternative baffle, inlet and outlet configurations, thereby, addressing a major knowledge gap in waste stabilisation pond design.
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    Aerobic thermophilic composting of piggery solid wastes : a thesis presented in partial fulfilment of the requirement for the degree of Doctor of Philosophy in Environmental Engineering at Massey University
    (Massey University, 2001) Pandey, Surya Prakash
    Commercial piggery operations produce substantial quantities of solid waste requiring further treatment and disposal. Screened piggery solids contain recyclable nutrients and pathogenic organisms. Point source contribution from piggeries to surface and ground water pollution can be minimised by the application of composting process and technology. This process can serve as the treatment component of an overall waste management plan of a commercial piggery to biologically convert the putrescible to a stabilised form free of pathogenic organisms. The rate of biochemical reaction determines the speed at which composting can proceed. Solids Retention Time (SRT) is the most important factor in determining the stability of the compost product. SRT is function of, among many other factors, the type of substrate and amendments and their corresponding reaction rate constants. In order to establish the minimum SRT, it is important to correctly derive the reaction rate constant from decomposition data. Rates of decomposition vary widely depending on the organic substrate. Although numerous guidelines are available for the design of effective composting plant, most of these guidelines or studies deal with sewage sludge or municipal solid waste. There is a complete lack of data on composting process design or reaction rates for piggery solids. Due to these specific concerns, the main objectives of this thesis were to examine the composting process in relation to bulking material and operating conditions; analyse the disappearance of Total Organic Carbon with temperature development in order to determine first order reaction rates; and to analyse the inactivation or decay of indicator pathogens in piggery solids and sawdust composting trials and experiments. Aerobic static pile composting of piggery solids was investigated at pilot (5 m3) scale. Sawdust was used as the bulking agent to provide additional carbon and to increase the porosity of the substrate. Composting trials, using different substrate to bulking agent ratios and aeration frequencies were performed. The composting mixture was placed over an aerated base in the form of a pile. Temperature development, pH, Total Nitrogen. Total Phosphorus, Total Organic Carbon, Total Solids, Volatile Solids and pathogenic indicators were monitored until the completion of the trial. The development of temperature profiles in three layers of the pile in each trial was similar and in agreement with trials conducted by various researchers. The change in moisture levels at two sampling points within the compost heap for each trial were similar. The moisture removal results demonstrated that the moisture removal from the compost pile depends not only upon a suitable temperature range, but also on the mode of heat movement. The increase in Total Solids and decrease in the fraction of Volatile Solids during the composting period in many trials were in agreement with trends described by many authors and demonstrated the decomposition process. The nutrient analysis showed that up to 75% of initial nitrogen was conserved in the compost while there was no significant change in phosphorus concentration. There was varying order of magnitude reduction in Streptococci numbers in different trials. Similar trends were observed for total coliform(MPN) reduction. The high temperatures of the pile for prolonged periods were expected to decrease the bacterial counts to levels lower than those observed. The high values of MPN indicate that there are certain spore formers which survive the composting process. The decomposition curve of Total Organic Carbon was used to calculate rate constant (k) over time from the temperature development data. A medium-order. Newton-Raphson algorithm, which solved non-stiff differential equation was used to solve the reaction rate equation numerically. Two models were compared for the determination of reaction rate constant. Values of reaction rate constant varied under different operating conditions of compost piles. The best values of reaction rate constant of the order of 0.008 and 0.007 per day were obtained from trial 4 that used a 25:75 (volume basis) sawdust-waste ratio; and was aerated for 10 minuted every hour. Same trial had the lowest Mean Residence Time (MRT) of approximately 115days. Two controlled laboratory experiments at 70 °C and 60 °C, respectively were also performed to independently verify rate constants developed from pilot trials. Laboratory experiments gave similar reaction rate constants to those mentioned above. This is beside the fact that a constant temperature profile was maintained throughout the composting period in these two experiments. The average residence time of solids under controlled conditions was not very different from MRT values obtained in the same pilot trial. A comparison of two models showed that a simple first-order kinetic model can be used for the determination of inactivation coefficient, but using Arrhenius equation incorporating the reference temperature would provide a better thermal inactivation coefficient estimates. In trial 4, inactivation rate coefficient values were of the order of 0.394 and 0.380 per day at two sampling positions, respectively. The laboratory experiments provided inactivation rate coefficient values of the order of 61.97 and 47.34 per day, respectively. The significant difference in the reduction of indicator microorganisms between pilot trials and controlled experiments emphasises that homogeneity is critical in any composting process. It also emphasises the need for a temperature feedback aeration system.
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    Biosorption and leaching of heavy metals from activated sludge applied to soil : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Technology at Massey University, Palmerston North, New Zealand
    (Massey University, 2002) Mahenthiran, Pushpalatha
    Accumulation of heavy metals in sewage sludge and soil and their subsequent movement to ground water and surface water are major environmental issues. Cadmium (Cd), copper (Cu), zinc (Zn), nickel (Ni) and chromium (Cr) are the most commonly occurring sludge-borne heavy metals in New Zealand. The potential toxicity of these heavy metals depends more on their availability and mobility than on their total content. This study examined the adsorption-desorption and potential leachability of these heavy metals in sewage sludge and a volcanic soil. Results of adsorption - desorption experiments using Cd, Cu, Zn and Ni showed that activated sewage sludge sorbed Cd, Cu and Zn more effectively than Ni. Adsorption capacities of Cd, Cu and Zn were 35.7-44.8, 14.1-26.4 and 57.5-59.5 mg/g biomass, respectively. The affinity of activated sewage sludge with Ni was very low thereby no further isotherm study was carried in Ni. Biosorption increased with increases in pH. Adsorption capacity also increased with increases in initial metal ion concentration but the adsorption yield decreased. Chloride ion concentration (0.145 N) had a more significant effect on the reduction of adsorption of Cd than on the reduction of the adsorption of either Cu or Zn. A desorption study was carried out using deionized water, 0.1 N Na2SO4,0.1 N K2SO4,0.1 M Na citrate, and 0.1 M Na2CO3 solutions and the results showed that Zn desorbed more in every desorbing agent. Results of the study of the adsorption behaviour of Zn in volcanic Egmont soil in the presence of phosphate showed an increase in adsorption of Zn and the presence of nitrate did not show any significant difference in adsorption. Both 500 and 1000 mg/kg phosphate levels reduced the water-soluble Zn in volcanic Egmont soil remarkably. The desorption study showed that more Zn was desorbed with 0.1 M KNO3 than with deionized water and 0.1 M KH2PO4. An in situ leaching study was carried out in volcanic Egmont soil using Zn amended sewage sludge and inorganic Zn as Zn sources and soil columns were pretreated with nitrate and phosphate anions. More Zn leached from inorganic Zn applied soil columns than from Zn amended sewage sludge applied soil columns. There was no substantial difference in the amount of Zn leached between nitrate and phosphate treated columns. Determination of total acid digestible Zn in sewage sludge and inorganic Zn applied soils showed a greater accumulation of Zn in 0-10 cm depth. More Zn moved to the lowest (25-32 cm) depth in the nitrate treated inorganic Zn applied soil column and less Zn moved to the lowest (25-32 cm) soil depth in the phosphate treated sewage sludge applied column. Fractionation of Zn in Zn amended sewage sludge showed that most of the fractions of Zn were in water-soluble and exchangeable, followed by carbonate and organically complexed forms. However, fractionation of Zn in control volcanic Egmont soil showed that most of the Zn was in oxide and residual forms. After the application of both Zn amended sewage sludge and inorganic Zn, the overall percentages of water-soluble and the exchangeable, carbonate and organically complexed forms of total Zn increased. All the fractions of Zn in both sludge and inorganic Zn applied columns decreased with the increase in soil depthFractionation of Zn in inorganic Zn applied soil showed that the increase in the exchangeable and oxide forms of Zn was higher in the phosphate than in the nitrate treatment. The overall percentage of the water-soluble and the exchangeable and the carbonate forms of total Zn increased except the organic, the oxide and the residual form in inorganic Zn applied soil columns. The results of this study suggest that activated sewage sludge has a high affinity for Cd, Zn and Cu. Zn desorbed from sewage sludge more easily than Cu indicating that the Zn from the sewage sludge may be more reactive than Cu in soil. Ex situ and in situ studies showed that phosphate remarkably limited the Zn movement in both sewage sludge and inorganic Zn applied soils but nitrate did not have any significant impact on the movement of Zn.
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    Treatment of meat processing wastewater for carbon, nitrogen and phosphorus removal in a sequencing batch reactor : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Process & Environmental Technology at Massey University
    (Massey University, 2002) Thayalakumaran, Nagalingam
    The typical New Zealand meat processing industry wastewater was treated by a laboratory scale Sequencing Batch Reactor (SBR) to determine an effective operating cycle for biological carbon, nitrogen and phosphorus removal. The Activated Sludge Model No. 1 and Model No. 2 with modifications were used to simulate the treatment of meat processing wastewater using the SBR. The average values of main pollution parameters of the wastewater were characterised as 1390 mg total COD L-1, 755 mg soluble COD L-1, 75 mg L-1 NH3 - N, 145 mg L-1 TKN and 34 mg L-1 TP. The readily biodegradable COD (RBCOD) accounts for 15 - 18% of the total COD, while the inert soluble and particulate portion were 4% each. In order to establish an effective operating cycle for the simultaneous removal of nutrients and organic carbon, different dissolved oxygen (DO) concentrations in the mixed liquor, duration of operating phases and hydraulic retention time (HRT) of a 6 h cycle were tested. The most effective cycle consisted of seven phases. The first two hours of the anaerobic period was followed by the aerobic and anoxic periods. The first aerobic period was maintained at a DO concentration of 0.5 ±0.25 mg L-1 for 1 h, the second aerobic period for 1 h at a DO concentration of 3.75 ±0.25 mg L-1 and the third aerobic period for half an hour at 0.5 ±0.25 mg L-1 DO concentration. A half an hour anoxic period followed the first aerobic period. A settling period of 0.75 h followed the third aerobic period. The last quarter of an hour was for decanting and idling. The solids retention time (SRT) was 15 d, while the HRT was 2.5 d. Greater than 99% removal of biodegradable soluble COD, NH3 - N and PO4 - P was achieved in the effective operating cycle where the TN and TP in the wastewater were reduced to 10 mg L-1 and 1.0 mg L-1, respectively. In addition the soluble COD was reduced to 98 mg L-1. The key kinetic and stoichiometric parameters for ASM 1 and ASM 2 models were determined using batch tests. The heterotrophic maximum specific growth rate, yield coefficient and the half saturation constant were 2.0 d-1, 0.63 mg cell COD (mg COD)-1 and 8 mg L-1 respectively. The maximum specific growth rate of autotrophs was 0.65 - 0.80 d-1. The anaerobic phosphorus removal stoichiometric coefficients were also determined in batch tests. During the anaerobic period, when 1 g of acetate COD was initially present, 1.48 g of PHA COD was stored while 0.48 g of P was released. The batch trials conducted using acetate to assess the influence of Mg2+ in P uptake showed that the Mg2+ could limit the P uptake and the uptake rate could be represented by Monod type kinetics. In the Monod kinetic expression the Mg2+ half saturation constant was found to be 4.7 mg L-1 The molar ratio of Mg2+ with P was 0.21 during the anaerobic period, and 0.33 during the aerobic period. The SBR performance was modelled using ASM 1 and ASM 2 models after the addition of more processes in these models. Ammonification of the soluble organic N process rate was modified in the ASM 1 model. Similarly it was necessary to add anoxic P uptake and anoxic growth processes involving PHA of Bio-P bacteria in the ASM 2 model. Glycogen storage and glycogen lysis processes of Bio-P bacteria were added in the ASM 2 model to understand the involvement of glycogen in P removal. Also a modification was performed to the storage process of poly-P in the ASM 2 model to account for potential Mg2+ limitation in meat processing wastewater treatment for P removal. During the settling period anoxic hydrolysis was assumed to be negligible. The calibrated ASM 1 and ASM 2 models in general well simulated the effluent NH3 - N, NO3 - N and PO4- P of SBR cycles carried out in distinctly different periods of time and in different batch tests. As the calibrated modified ASM 2 model was able to predict the performance of an SBR cycle conducted over a time period of three months, it was used to identify the most promising treatment strategies of the SBR performance. Variation in duration of feed cycle during the first non-aerated mixed period did not affect the effluent NO3 - N, NH3 - N and PO4 - P concentrations significantly. DO concentration of 3.75 mg L-1 during the third aerobic period instead of 0.5 mg L-1 increased the effluent NO3 - N and PO4 - P concentrations. The simulations confirmed that the operating conditions identified in a 6-h cycle period for the simultaneous organic carbon and nutrient removal are effective.
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    A CFD modelling system for air flow and heat transfer in ventilated packing systems during forced-air cooling of fresh produce : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Engineering at Massey University
    (Massey University, 2002) Zou, Qian
    Forced-air cooling is the common method for precooling horticultural produce. Ventilated packaging systems are often used to facilitate cooling efficiency. A computational fluid dynamics (CFD) modelling system was developed to simulate airflow and heat transfer processes in the layered and bulk packaging systems during the forced-air cooling of fresh produce. Airflow and heat transfer models were developed using a porous media approach. The areas inside the packaging systems were categorised as solid, plain air, and produce-air regions. The produce-air regions inside the bulk packages or between trays in the layered packages were treated as porous media, in which the volume-average transport equations were employed. This approach avoids dealing with the situation-specific and complex geometries inside the packaging systems, and therefore enables the development of a general modelling system suitable for a wide range of packaging designs and produce. The calculation domains were discretised with a block-structured mesh system that was referenced by global and local grid systems. The global grid system specifies the positions of individual packages in a stack, and the local grid system describes the structural details inside individual package. The solution methods for airflow and heat transfer models were based on SIMPLER (Semi-Implicit Method for Pressure-Linked equations Revised) method schemes, and the systems of linear algebraic equations were solved with GMRES (Generalised Minimum Residual) method. A prototype software package CoolSimu was developed to implement the solution methods. The software package hid the core components (airflow and heat solvers) from user, so that the users without any knowledge of CFD and heat transfer can utilise the software to study cooling operations and package designs. The user interaction components in CoolSimu enable users to specify packaging systems and cooling conditions, control the simulation processes, and visualise the predicted airflow patterns and temperature profiles. When the predicted and measured product centre temperatures were compared during the forced-air cooling of fresh fruit in several layered and bulk packaging systems, good agreements between the model predictions and experimental data were obtained. Overall, the developed CFD modelling system predicted airflow patterns and temperature profiles with satisfactory accuracy.
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    Physiological measures related to crispness perception of extruded snacks : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology at Massey University, Albany, New Zealand
    (Massey University, 2003) Duizer, Lisa Marjorie
    Published research for understanding crispness perception has relied on correlations of sensory results to objective measurements. This research was undertaken to evaluate the contribution of physiological responses to the perception of crispness of corn based puffed snacks. Predictive models published in literature relate crispness perception to instrumental force and sounds produced during biting and compression. These models were used as the basis for this research. Air-conducted and bone-conducted sounds were measured using both consumer and trained panelists. A novel analysis technique, fractal analysis, was used to analyse the jagged sound wave patterns produced during biting into extruded snacks. A specialised bite force apparatus was designed for measuring bite forces produced by the incisors. All physiological results were then related to panelists' perception of crispness. To minimise sample variability, extruded snack samples were prepared and used throughout the entire trial. A range of crispness levels were achieved by equilibrating the extrudates over various water activities. Consumer panelists and trained panelists consistently agreed on the relative crispness of the extruded snacks. Air-conducted sounds and bite force showed significant correlations with crispness, while bone-conducted sounds did not. Bite force measures were also shown to relate to instrumental measures of force. For statistical validity, the physiological data from the 39 consumers were used to develop predictive equations for crispness. Analysis of the data showed no significant correlation between the physiological data and crispness. Therefore, it was not possible to develop a predictive equation for crispness based on the physiological measures collected from consumers. While there are reports linking crispness to various instrumental measures, this is the first time in-vivo physiological measures have been collected from a large group of individuals for development of statistically viable models for crispness. The lack of a relationship between crispness and physiological measures indicates that crispness perception across consumers is complex and not adequately explained by bite force and sounds alone.
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    Prediction of the thermal conductivity of porous foods : a thesis submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Engineering, Massey University, Palmerston North, New Zealand, 2002
    (Massey University, 2002) Carson, James K
    A review of the food engineering literature exposed a paucity of information in the area of effective thermal conductivity prediction for porous foods. No useful guidelines were found that could advise a food engineer on the selection of appropriate effective thermal conductivity models for this application. The aims of this study were to increase the understanding in this area and to produce a general procedure for effective thermal conductivity prediction. The specific focus of this study was the influence of porosity on thermal conduction and so the porous foods under consideration were assumed to contain small (<5mm), uniformly distributed void spaces filled with stagnant gas (either air or carbon dioxide), in order that convection and radiation effects could be neglected. It was also assumed that only bound water was present within foods so that moisture migration and its associated heat effects would not be an issue. Two basic classes of porous foods were identified: foods in which void spaces existed in the interstices of particulate foods were referred to as having "external porosity" and foods in which bubbles existed within a solid or liquid matrix were referred to as having "internal porosity". Using a comparative method, thermal conductivity measurements were performed on food analogues comprised of expanded polystyrene (EPS) beads suspended in guar gel. Thermal conductivity data were produced that revealed a basic dependence of the relative effective thermal conductivity (ke/kl) on the porosity (v2) The mean volume of the individual EPS beads used to simulate the air bubbles was varied between 10-6 and 4x10-3 of the total sample volume, but no significant dependence of ke/kl on bead diameter was observed. Thermal conductivity measurements were also performed on samples containing squat aluminium cylinders suspended in guar gel. The results from these samples highlighted the significant influence of the component thermal conductivity on the uncertainties involved in effective thermal conductivity prediction. Using a finite element software package, two-dimensional numerical models were constructed to simulate the measurement of effective thermal conductivity for theoretical material samples having different basic structures. These models allowed the relative significance of several structure-related variables to be examined. The results indicated that the status of the gaseous and solid/liquid components of porous foods, whether continuous or dispersed, and the degree to which pores (in the case of internal porosity) or particles (in the case of external porosity) were in contact with neighbouring pores or particles had a significant influence on the effective thermal conductivity. The sizes and shapes of the individual pores or particles were found to have only minor or negligible influence. The predictions from two basic types of models were compared to the results from the physical experiments: those models that were functions of component thermal conductivity and volume fractions only (referred to as Type A models), and those that were functions of these two variables as well a third variable (referred to as Type B models). None of the Type A models provided accurate predictions for all the experimental data considered and it was concluded that, apart from certain scenarios, the use of Type B models was preferable. Of the Type B models considered, those that were based on isotropic physical models such as the Maxwell and Effective Medium Theory (EMT) based models, provided better predictions on average than those based on anisotropic physical models, such as the Krischer and Chaudhary-Bhandari models. The analysis of the experiments and the results of the model evaluation exercise highlighted an important issue regarding the selection of appropriate effective thermal conductivity models: the effective thermal conductivity of the materials had a strong dependence on the optimum heat conduction pathway for a given structure. Hence an assessment of a material's structure should be performed in order to determine the optimum heat conduction pathway within that material. Two basic optimal heat conduction pathways were identified. In the first scenario the continuous phase of the material has a higher thermal conductivity than the dispersed phase, as is the case with materials having internal porosity, and the optimum heat conduction pathway avoids the gas bubbles that comprise the dispersed phase. In the second scenario, the continuous phase has a lower thermal conductivity than the dispersed phase, as is the case with materials having external porosity, and the optimum heat conduction pathway passes through as many of the solid particles that comprise the dispersed phase as possible. Previous workers have shown that the two forms of the Maxwell-Eucken model provided theoretical upper and lower limits of the effective thermal conductivity of isotropic materials. In this work, it was proposed that the effective thermal conductivities of materials having internal porosity are bounded by the Landauer-EMT model and the form of the Maxwell-Eucken model in which the continuous phase has a higher thermal conductivity than the dispersed phase. Similarly, it was proposed that the effective thermal conductivities of materials having external porosity are bounded by the Landauer-EMT model and the form of the Maxwell-Eucken model in which the continuous phase has a lower thermal conductivity than the dispersed phase. The degree of contact between the pores or particles of the dispersed phase, which was related to the optimum conduction pathway, was identified as the variable having the most significant influence on a material's thermal conductivity, in terms of its position relative to thermal conductivity bounds. For this reason, effective thermal conductivity models for general applications should incorporate some measure of this variable. For isotropic, non-frozen foods, two new models based on the Maxwell and EMT structural models with structure-related parameters were proposed. An advantage of these models was that the values of the structure-related parameters had linear variation between the thermal conductivity bounds, unlike other models in the literature. A simple, general procedure for predicting the effective thermal conductivity of isotropic non-frozen foods was proposed and tested on two types of cake. The predictions from the models recommended by the procedure for the cakes agreed with the experimental data to within ±10%, which would be sufficient for many food industry purposes. It was recommended that further testing of the proposed thermal conductivity prediction procedure be performed to assess its accuracy and practicality. A need to improve the understanding of the relationship between the structure-related model parameter and the extent of contact between pores or particles was also identified.