by Wai Yin Karen Fong. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1996. / Includes bibliographical references (leaves [106]-[110]). / Abstract --- p.2 / Acknowledgments --- p.3 / Dedication --- p.4 / Abbreviations --- p.5 / Table of Contents --- p.7 / Chapter Chapter 1: --- Introduction --- p.11 / Chapter 1.1 --- Overviews of packaging materials --- p.11 / Chapter 1.2 --- Source of contamination --- p.14 / Chapter 1.2.1 --- Contamination from packaging materials --- p.15 / Chapter 1.2.2 --- Contamination of plasticisers from packaging materials and its effect --- p.16 / Chapter 1.3 --- Classification of commercial plasticisers --- p.19 / Chapter 1.3.1 --- Application of plasticisers --- p.20 / Chapter 1.4 --- Analysis of the plasticisers in the food packaging films --- p.22 / Chapter 1.5 --- Analysis of plasticisers in food using isotope dilution technique --- p.22 / Chapter Chapter 2 --- : Instrumentation and Analytical methods --- p.25 / Chapter 2.0 --- Instrumentation --- p.25 / Chapter 2.1 --- Gas chromatography --- p.25 / Chapter 2.2 --- Detector --- p.26 / Chapter 2.2.1 --- Flame ionisation detector --- p.26 / Chapter 2.2.2 --- Mass spectrometer --- p.27 / Chapter 2.2.2.1 --- Ion trap detector --- p.28 / Chapter 2.2.3 --- Ionisation mode --- p.33 / Chapter 2.2.3.1 --- Electron ionisation (EI) --- p.33 / Chapter 2.2.3.2 --- Chemical ionisation (CI) --- p.34 / Chapter 2.4 --- Analytical methods --- p.36 / Chapter 2.3 --- The use of combined GC/MS in the analysis of plasticisers --- p.36 / Chapter 2.3.1 --- Identification by GC/MS --- p.37 / Chapter 2.3.2 --- Qualitative MS --- p.37 / Chapter 2.3.3 --- Quantitative MS --- p.39 / Chapter 2.3.3.1 --- Isotope dilution technique --- p.40 / Chapter Chapter 3: --- Analysis of plasticisers in food packaging materials --- p.41 / Chapter 3.1 --- Introduction --- p.41 / Chapter 3.2 --- Experimental and Instrumental --- p.42 / Chapter 3.2.1 --- Reagents --- p.43 / Chapter 3.2.2 --- Materials --- p.43 / Chapter 3.3 --- Identification of food packaging materials --- p.43 / Chapter 3.3.1 --- Fourier transform infrared spectrometry --- p.44 / Chapter 3.3.2 --- Burning test --- p.45 / Chapter 3.3.3 --- Solvent dissolution method --- p.46 / Chapter 3.4 --- Extraction of plasticisers from the packaging materials --- p.49 / Chapter 3.4.1 --- Chloroform extraction --- p.50 / Chapter 3.4.2 --- Solvent reflux method --- p.50 / Chapter 3.5 --- Results and discussion --- p.51 / Chapter 3.5.1 --- Precision test --- p.51 / Chapter 3.5.2 --- Calibration curve --- p.52 / Chapter 3.5.3 --- Detection limit --- p.54 / Chapter 3.5.4 --- Recovery --- p.54 / Chapter 3.6 --- Survey of the level of plasticisers in food packaging materials --- p.55 / Chapter 3.7 --- Conclusion --- p.66 / Chapter 4.0 --- Analysis of plasticisers in foods --- p.67 / Chapter 4.1 --- Introduction --- p.67 / Chapter 4.2 --- Experimental and instrument --- p.67 / Chapter 4.2.1 --- Reagents --- p.68 / Chapter 4.2.2 --- Materials --- p.68 / Chapter 4.3 --- Analysis --- p.69 / Chapter 4.3.1 --- selection of stable isotope labelled analogues --- p.69 / Chapter 4.3.2 --- Synthesis of deuterated internal standard --- p.70 / Chapter 4.4 --- Extraction of foods --- p.71 / Chapter 4.4.1 --- Clean up method --- p.73 / Chapter 4.4.2 --- Quantitation --- p.77 / Chapter 4.5 --- Results and discussion --- p.82 / Chapter 4.5.1 --- Precision test --- p.82 / Chapter 4.5.2 --- Calibration curve --- p.84 / Chapter 4.5.3 --- Detection limit --- p.85 / Chapter 4.5.4 --- Survey of the level of plasticisers in food --- p.86 / Chapter 4.6 --- Conclusion --- p.91 / Chapter 5.0 --- Analysis of plasticisers in food by EI and CI method / Chapter 5.1 --- Introduction --- p.93 / Chapter 5.2 --- Experimental and Instrumental --- p.94 / Chapter 5.2.1 --- Reagents --- p.95 / Chapter 5.2.2 --- Materials --- p.95 / Chapter 5.3 --- Extraction of foods --- p.95 / Chapter 5.3.1 --- Clean up method --- p.95 / Chapter 5.4 --- Result and discussion --- p.95 / Chapter 5.4.1 --- Precision test --- p.95 / Chapter 5.4.2 --- Calibration curve --- p.97 / Chapter 5.4.3 --- Detection limit --- p.99 / Chapter 5.4.4 --- Survey of plasticisers in food by EI and CI method --- p.100 / Chapter 5.4.5 --- Paired t-Test --- p.103 / Chapter 5.5 --- Conclusion --- p.104 / Chapter Chapter 6 --- Conclusion --- p.105 / Bibliography --- p.106 / Appendices : / Chapter 1 --- The mass spectrum of DEP --- p.i / Chapter 2 --- The mass spectrum of DIBA --- p.i / Chapter 3 --- The mass spectrum of DIBP --- p.ii / Chapter 4 --- The mass spectrum of DBP --- p.ii / Chapter 5 --- The mass spectrum of DBS --- p.iii / Chapter 6 --- The mass spectrum of ATBC --- p.iii / Chapter 7 --- The mass spectrum of BBP --- p.iv / Chapter 8 --- The mass spectrum of DEHA --- p.iv / Chapter 9 --- The mass spectrum of DPOP --- p.v / Chapter 10 --- The mass spectrum of DEHP --- p.v / Chapter 11 --- The mass spectrum of DCHP --- p.vi / Chapter 12 --- The mass spectrum of DOAZ --- p.vi / Chapter 13 --- The mass spectrum of DOS --- p.vii / Chapter 14 --- Calibration curve of GC/FID --- p.viii / Chapter 15 --- Calibration curve of GC/MS (magnum) --- p.xi / Chapter 16 --- Calibration curve of GC/MS (GCQ) --- p.xiv

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No description available.

Aunque la plata se usa como componente clave en el control microbiano en incontables aplicaciones, las tecnologías basadas en plata disponibles son escasas. Esto radica en la dificultad para evaluar su eficacia debido a problemas de estabilidad y de especiación. En la presente tesis, iones de plata fueron incorporados en matrices biopoliméricas para obtener materiales de prolongada capacidad antimicrobiana basados en su liberación sostenida. Se realizó un estudio profundo de las interacciones químicas entre las especies activas de plata, las bacterias, y posibles ligandos presentes en el medio de acción. En condiciones óptimas, la plata demostró ser eficaz en el rango de los nanomoles. Sin embargo, interacciones químicas con varios ligandos afectaron drásticamente tanto su eficacia como la evaluación de la viabilidad bacteriana. La incorporación de iones de plata en películas de EVOH no alteró las propiedades físico-químicas de los materiales que mostraron una rápida liberación del contenido de plata al entrar en contacto con la humedad. Esto se reflejó en la inactivación de las bacterias a concentraciones muy bajas (0.0001wt.%) en condiciones óptimas. Cuando se incorporaron iones de plata en PLA por casting o mezclado-fundido, la liberación y el rendimiento antimicrobiano se prolongaron de días a meses, dependiendo del contenido, el método de incorporación, la humedad o el pH del medio de liberación. Una etapa inicial de liberación mayor pudo ser atenuada gracias a la aplicación de una capa de cera de abejas, lo que permitió adaptar los perfiles de liberación a demanda y cumplir con la legislación vigente en diversas condiciones de liberación. Las películas demostraron un alto efecto antibacteriano y antiviral contra los patógenos transmitidos por los alimentos más comunes en medios sintéticos, en superficie y en alimentos líquidos y sólidos. Este estudio representa un avance en la comprensión de la eficacia antimicrobiana de la plata y destaca su posible idoneidad para la fabricación de materiales de envasado de alimentos, de contacto con alimentos u otras aplicaciones. / Martínez Abad, A. (2014). Development of silver based antimicrobial films for coating and food packaging applications [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/36738 / TESIS / Premios Extraordinarios de tesis doctorales

Tesis por compendio / [ES] La presente tesis doctoral tuvo como objetivo desarrollar nuevos materiales biodegradables hechos a base de fibras obtenidas mediante la técnica de electroestirado, denominadas "biopapers" o biopapeles, con barrera a agua y a gases y propiedades de secuestro de oxígeno para su posible aplicación en recubrimientos de papel o como capas intermedias en envases alimentarios basados en papel y cartón. En un primer estudio, se desarrollaron biopapeles de PHB mediante electroestirado, usando dos tipos de colectores, colectores de placa plana y rotativo, para evaluar la influencia del alineamiento de las fibras. Con posterioridad se aplicó un tratamento de recocido por debajo del punto de fusión del polímero a diferentes temperaturas, tiempos y procesos de enfriamiento para obtener películas continuas por coalescencia de las fibras, lo que a su vez condujo a la adhesión entre capas, y a una mejora en las propriedades barrera y ópticas. En un segundo estudio, se depositaron biopapeles monocapa y multicapa hechos de PHB, PVOH y PLA sobre un sustrato de papel no estucado, utilizando los dos colectores citados; y el tiempo de procesamiento por electrospinning se varió para producir espesores diferentes. Para mejorar la adhesión al sustrato de papel, y las propiedades ópticas y de barrera de las multicapas, los biopapeles se sometieron a un proceso de recocido como se describe y optimiza en el primer estudio. Con respecto a la barrera al agua, el sistema de papel/ PVOH/PHB presentó las mejores propriedades. En un tercer estudio, se obtuvieron dos nanopapeles de alta barrera hechos a base de nanofibras de celulosa de dos tipos, nanofibras de celulosa (CNF) y nanofibras de lignocelulosa (LCNF) y se recubrieron con biopapeles de PHA electroestirados con barrera a agua. Como resultado, el carácter hidrófobo de los nanopapeles se mejoró significativamente. Por otra parte, estos también exhibieron un rendimiento mecánico más equilibrado. En un cuarto estudio, se desarrollaron biopapeles de PHA con capacidad activa de secuestro de oxígeno, para lo cual se usaron nanopartículas de paladio (PdNP) como catalizadores de la respuesta activa. La principal dificultad asociada con las nanopartículas es mantenerlas dispersas, por lo que en este trabajo evaluamos el uso de surfactantes CTAB y TEOS como sustancias permitidas en contacto con alimentos para ayudar a la dispersión y distribución de PdNP dentro de las fibras de PHA. Como resultado, se prepararon nanocompuestos electroestirados con capacidad de secuestro de oxígeno hechos de PHB y PdNP, seguidos de un tratamiento de recocido para obtener capas continuas y autoadhesivas. La capacidad de secuestro de oxígeno de los biopapeles, medida a un 100% de humedad relativa (HR), mostró un mejor rendimento para el material en forma de fibra que en forma de film. En cualquier caso, los resultados indicaron una cinética de absorcion relativamente baja. Con el fin de mejorar aún más la cinética de secuestro de oxígeno, incluso a una humedad intermedia y en forma de película, un quinto estudio, desarrolló biopapeles multicapa hechos de PCL y PHA aplicados sobre papel no estucado. Los nanocompuestos de PCL/PdNP mostraron uma cinética de secuestro de oxígeno mucho mayor que la del sistema PHA / PdNP anterior. Este resultado se atribuye a la mayor fración de volumen libre del PCL que permite que la humedad, el hidrógeno y la permeación de oxígeno desencadenen la reacción de eliminación catalítica de forma más eficiente. Finalmente, un sexto estudio, desarrolló un nuevo concepto de capa con capacidad de secuestro de oxígeno y con alta barrera passiva a gases y vapores orgánicos basado en PdNP, CNC y EVOH. Así, CNC y CNC oxidado com TEMPO (TEMPO oxidized CNC), se utilizaron para producir PdNP in situ sobre el nanorefuerzo, que se incorporaron en la matriz del polímero EVOH. El TEMPO oxidized CNC demostró poseer una mayor absorción de oxígeno debido a los grupos car / [CA] La present tesi doctoral va tindre com a objectiu desenvolupar noves capes biodegradables actives obtingudes mitjançant electrospinning, denominades "biopapers" o biopapeles, amb barrera a aigua i a gasos i propietats de segrest d'oxigen per a la seua possible aplicació en recobriments de paper o com a capes intermèdies en envasos alimentaris basats en paper i cartó. En un primer estudi, es van desenvolupar bio-papers de PHB mitjançant electrospinning, utilitzant dos tipus de col·lectors, col·lectors de placa plana i rotatiu, per a avaluar la influència de l'alineament de les fibres. Amb posterioritat es va aplicar un tractament de recuita per davall del punt de fusió del polímer a diferents temperatures, temps i processos de refredament per a obtenir pel·lícules contínues per coalescència de les fibres, la qual cosa al seu torn va conduir a l'adhesió entre capes, i a una millora en les propietats barrera i òptiques. En un segon estudi, es van depositar bio-papers monocapa i multicapa fets de PHB, PVOH i PLA sobre un substrat de paper no estucat, utilitzant els dos col·lectors citats; i el temps de processament per electrospinning es va variar per a produir grossàries diferents. Per a millorar l'adhesió al substrat de paper, i les propietats òptiques i de barrera de les multicapes, els biopapers es van sotmetre a un procés de recuita com es descriu i optimitza en el primer estudi. Respecte a la barrera a l'aigua, el sistema de paper/PVOH/PHB va presentar les millors propietats. En un tercer estudi, es van obtenir dos nano-papers d'alta barrera fets a base de nanofibres de cel·lulosa de dos tipus, nanofibres de cel·lulosa (CNF) i nanofibres de lignocel·lulosa (LCNF) i es van recobrir amb bio-papers de PHA electro-estirats amb barrera a aigua. Com a resultat, el caràcter hidròfob dels nano-papers es va millorar significativament. D'altra banda, aquests també van exhibir un rendiment mecànic més equilibrat. En un quart estudi, es van desenvolupar bio-papers de PHA amb capacitat activa de segrest d'oxigen, per a això es van usar nanopartícules de pal·ladi (PdNP) com a catalitzadors de la resposta activa. La principal dificultat associada amb les nanopartícules és mantenir-les disperses, per la qual cosa en aquest treball avaluem l'ús de surfactants CTAB i TEOS com a substàncies permeses en contacte amb aliments per a ajudar la dispersió i distribució de PdNP dins de les fibres de PHA. Com a resultat, es van preparar nano-compostos electro-estirats amb capacitat de segrest d'oxigen fets de PHB i PdNP, seguits d'un tractament de recuita per a obtenir capes contínues i autoadhesives. La capacitat de segrest d'oxigen dels bio-papers, mesurada a un 100% d'humitat relativa (HR), va mostrar un millor rendiment per al material en forma de fibra que en forma de film. En qualsevol cas, els resultats van indicar una cinètica de absorció relativament baixa. Amb la finalitat de millorar encara més la cinètica de segrest d'oxigen, fins i tot a una humitat intermèdia i en forma de pel·lícula, un cinquè estudi, va desenvolupar bio-papers multicapa fets de PCL i PHA aplicats sobre paper no estucat. Els nano-compostos de PCL/PdNP van mostrar una cinètica de segrest d'oxigen molt major que la del sistema PHA/PdNP anterior. Aquest resultat s'atribueix a la major fracció de volum lliure del PCL que permet que la humitat, l'hidrogen i la permeància d'oxigen desencadenen la reacció d'eliminació catalítica de forma més eficient. Finalment, un sisè estudi, va desenvolupar un nou concepte de capa amb capacitat de segrest d'oxigen i amb alta barrera passiva a gasos i vapors orgànics basat en PdNP, CNC i EVOH. Així, CNC i CNC oxidat com TEMPO (TEMPO oxidat CNC), es van utilitzar per a produir PdNP in situ sobre el nano-reforç, que es van incorporar en la matriu del polímer EVOH. El TEMPO oxidat CNC va demostrar posseir una major absorció d'oxigen degut als grups carboxílics generats. / [EN] The present PhD thesis aimed to develop novel active fiber based biodegradable layers obtained by electrospinning, so-called biopapers, with water and gas barrier and oxygen scavenging properties for their potential use as paper coatings or packaging interlayers in fiber based packaging. In a first study, PHB biopapers were obtained by electrospinning, by means of two types of collectors namely, flat plate and rotation drum collectors, to evaluate the influence of the alignment of fibers. Annealing post-processing below the polymer melting point was carried at different temperatures, isothermal times and cooling processes to obtain transparent and pore free continuous films by fibers coalescence which in turn led to interlayer adhesion, enhanced barrier and optical properties. In a second study, mono and multilayer biopapers comprising PHB, PVOH and PLA were deposited onto a conventional uncoated paper substrate, using the cited two collectors; and the electrospinning processing time was varied to produce different thickneses. To enhance adhesion to the paper substrate, optical and barrier performance of the multilayer, the biopapers were subjected to an annealed process as described and optimized in the first study. Regarding water barrier, the system paper/PVOH/PHB presented the highest barrier performance. In a third study, environmentally friendly materials such as cellulose based nanopapers, i.e. gas barrier layers made of cellulose nanofibrils (CNFs) and lignocellulose nanofibrils (LCNFs), were obtained and coated with the water barrier electrospun PHA biopapers. As a result, the hydrophobic character of the nanopapers was significantly improved by the electrospun biopapers. Moreover, these also exhibited a more balanced mechanical performance. In a fourth study, active oxygen scavenging PHA biopapers were developed, in which palladium nanoparticles (PdNP) were used as catalysts to scavenge oxygen from the headspace. The main difficulty associated with nanoparticles is to keep them dispersed, so in this work we assessed the use of CTAB and TEOS surfactants as food contact permitted substances to help dispersion and distribution of the PdNP within the PHA fibers. As a result, oxygen scavenging nanocomposite biopapers made of electrospun PHB and PdNP were prepared, followed by annealing treatment to obtain homogeneous and continuous active layers. The oxygen scavenging capacity at 100% relative humidity (RH) of the biopapers in fiber form showed better performance than their annealed specimens as expected, but in general this was not considered optimal. In order to improve further the oxygen scavenging capacity, even at a low relative humidity and in film form, a fifth study, developed multilayered biopapers made of PCL and PHA coated on conventional cellulose paper. The PCL/PdNP nanocomposites showed much more enhanced oxygen scavenging performance in comparison with the above PHA/PdNP system. This result is attributed to the higher fractional free volume of the PCL polymer that allows moisture, hydrogen and oxygen permeation to trigger the catalytic scavenging reaction. Finally, a sixth study, developed a solvent casting high gas barrier and active oxygen scavenging layer concept based on PdNP, CNC and EVOH. Thus, CNC and TEMPO oxidized CNC, were used to produce in situ PdNP, which were incorporated into the EVOH polymer matrix. The TEMPO oxidized CNC exhibited higher oxygen absorption due to the generated carboxylic groups. / Spanish Ministry of Economy and Competitiveness (MINECO) project AGL2015-63855-C2-1-R for financial support. A. Cherpinski also would like to thank the Brazilian Council for Scientific and Technological Development (CNPq) of Brasilian Government for her predoctoral grant (205955/2014-2). A. Cherpinski also acknowledges the European Cooperation in Science and Technology (COST) Action FP1405 for funding through a Short Term Scientific Mission (STSM) / Cherpinski Correa, A. (2019). NOVEL ELECTROSPUN POLYHYDROXYALKANOATE BASED HIGH BARRIER AND ACTIVE BIOPAPERS OF INTEREST IN FOOD PACKAGING [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/123064 / TESIS / Compendio

No description available.

A major problem associated with the development of complex polymeric materials for food contact applications is the potential for migration of toxic substances from the polymer to the food. This thesis investigates the transfer of migrants from non-ovenable food contact materials at elevated temperatures, and several applications where migration has occurred have been identified. Boil in the bag applications lead to exposure times of 30 - 120 minutes for complex multilayer laminates, whilst plastic kettles are repeat exposure items, and plastic 'vacuum flasks' have a potential for up to 4 hours exposure. Analytical techniques including, GC-MS, LC-MS, HPLC and UV spectroscopy have been employed to quantify the species migrating from these food contact materials into aqueous and oil simulants, and to ensure that they conform to the implemented EC restrictions. Olive oil is a stipulated EC fatty food simulant, but it is unsuitable for specific migration analyses since it contains many interfering compounds. These could not be eliminated by repeated solvent extraction, and a silicone oil was therefore substituted. In an attempt to identify the species migrating into aqueous and fatty food simulants both the final materials and also the individual components i.e. nylon, adhesive, polyethylene and polypropylene were examined separately. HPLC techniques have been developed to quantify both the known levels of antioxidants present in the polymers and also the anticipated degradation products from these materials. Typical levels of antioxidants in simulants range from <0.1 (aqueous) to 45j..lgdm-2 (oil) and <0.1 (aqueous) to 200j..lgdm" (oil) for antioxidant degradation products. In commercial boil in the bag laminates the major migrants have been shown to be derived principally from the nylon film, and the polyurethane adhesive used to fabricate the laminate. Le-MS investigations have confirmed the presence of the residual monomer Ecaprolactarn and its cyclic oligomers (up to the nonarner) in aqueous food simulants boiled in direct contact with the nylon 6. This technique has also identified the main migrants from the aliphatic and aromatic polyurethane adhesives to be residual oligomers from the polyols. Any residual isocyanates in the adhesive are converted to the corresponding amine, and colourimetric assays have determined levels between 1.1 and O.lj..lgdm". Measured, migration levels into fatty food simulants were found to be greater than in aqueous food simulants. However, none of the material examined showed an overall migration value greater than the EC limit of 10mg dm" for single sided testing. Some instances were found where the consumer was instructed to boil the dry food part of a boil in the bag meal in the same water as that used to heat the pouch containing the meat, and under these circumstances a total migration value for the laminate greater than 10mg dm-2 was measured.

by Lung Man Tung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1991. / Includes bibliographical references. / ACKNOWLEDGMENT --- p.i / ABSTRACT --- p.ii / Chapter CHAPTER 1 --- GENERAL INTRODUCTION --- p.1 / Chapter 1.1 --- Stationary phases and detectors --- p.2 / Chapter 1.2 --- Internal standardization --- p.5 / Chapter 1.3 --- Common pre-treatment technique --- p.6 / Chapter 1.4 --- Pre-treatment techniques --- p.9 / Chapter 1.5 --- Objectives of this work for the determination of styrene --- p.11 / Chapter CHAPTER 2 --- EXPERIMENTAL --- p.13 / Chapter 2.1 --- Instrumentation --- p.13 / Chapter 2.2 --- Reagents and solutions --- p.16 / Chapter 2.3 --- Preparation of stock solutions --- p.18 / Chapter 2.4 --- Sample preparation --- p.19 / Chapter 2.5 --- Extraction method for food samples --- p.20 / Chapter 2.6 --- Procedure for the analytical finish --- p.22 / Chapter 2.7 --- Assessment of the food matrix effect on the recovery of styrene --- p.23 / Chapter 2.8 --- Confirmatory Procedures --- p.23 / Chapter 2.9 --- Treatment of data --- p.24 / Chapter CHAPTER 3 --- DEVELOPMENT OF METHOD --- p.26 / Chapter 3.1 --- Development of GC method --- p.26 / Chapter 3.2 --- Development of the extraction method --- p.29 / Chapter CHAPTER 4 --- DETERMINATION OF RESIDUAL STYRENE IN POLYSTYRENE POLYMER --- p.50 / Chapter 4.1 --- The proposed method --- p.50 / Chapter 4.2 --- Identification of polymer and one cup for the ice-cream cone --- p.51 / Chapter 4.3 --- Determination of residual styrene monomer in polystyrene container and cup --- p.52 / Chapter CHAPTER 5 --- DETERMINATION OF STYRENE MONOMER MIGRATED INTO FOODSTUFFS --- p.58 / Chapter 5.1 --- Methodolgy and scope --- p.58 / Chapter 5.2 --- Determination of styrene migrated into ice-cream --- p.59 / Chapter 5.3 --- Determination of styrene migrated into Yakult and Yogo --- p.60 / Chapter 5.4 --- Determination of styrene migrated into foodstuff kept at elevated temperature in polystyrene containers --- p.60 / Chapter 5.5 --- Conclusion --- p.74 / REFERENCES --- p.76 / APPENDIX --- p.80

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The development of a simulation strategy and modelling algorithm with potential application to a variety of food process operations, particularly to thermal processing of canned foodstuffs has been undertaken. A review of published work identified previous efforts in the development of mathematical models for thennal process operations, including their limitations. The review showed that Finite Difference methods have found wide application in modelling conduction heating of canned foods. A similar model would be a useful numerical yardstick for validating any developments in this work. The great diversity of food handling operations have been grouped into a more manageable small number of classes. Such classification recognised that sets of related operations share common characteristics and functions which are the basis for the development of mathematical models for each class of operations. The strategy developed involved hierarchical decomposition of unit operations into assemblies of basic modules and mathematical modelling of these basics. A model of the operation can then be constructed simply by selecting and arranging the required basic units with due consideration to the boundary conditions of the physical problem. For transient operations with positional variation, these elementary modules have been termed "zones". The range of basic zones to model representative units have been identified. This hierarchical zone-model simulation has been demonstrated for heat transfer in a cylindrical container and for batch retort operation. The repeated use of the same unit modules for different operations makes this a flexible and robust strategy. The mathematics of zone-modelling has been developed for heat conduction in foodstuffs in cylindrical containers. To ensure accuracy, the numerical integration steps were rigorously monitored using mathematical procedures well-established for this purpose. The validity of the model has been tested against the analytical and implicit finite difference solutions. Generally, zone models agreed within 1 % of these standard yardsticks with the difference becoming negligible when sufficiently small integration steps or zone sizes were used. The effectiveness of zone-modelling as a simulation tool has been established using experimental data and the various sources of discrepancy between the model and experimental data accounted for. Thermocouple measurement errors have been found to have contributed most significantly to this discrepancy. Detailed analysis and modelling of thermocouple measurement errors has been carried out using zone-modelling to simulate the true experimental system which accounted for the presence of a thermocouple. The result has been an improved agreement between experiment and the zonemodel, and it also demonstrated the flexibility of the modelling technique. Further resuhs have shown that the discrepancy varied with thermocouple size and type. The contributions to error of temperature variability of, and of uncertainty in, thermophysical properties of the food were discussed. , The flexibility and robustness of zone-modelling have been further demonstrated using some practical situations including heat transfer to foodstuff in flexible packaging - such as sausage rolls, heat transfer in a food container with varying headspaces and the consequence of steam interruption during processing. Examples have been discussed of other transient processes that could similarly be modelled using this technique. The main achievements of this work include the application of hierarchical simulation and zonemodelling techniques to food processing and the development of a novel mathematical modelling technique which is more flexible than finite differences. Moreover, the applications of zonemodelling to the study of thermocouple errors, to the study of the consequences of steam interruption during thermal processing, and to heat transfer in foods in flexible containers, are developments of interest in food processing. It is concluded that the hierarchical simulation and zone modelling algorithm are robust and flexible techniques with potential applications in food process simulation .