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Der Produktschutz gilt als die wichtigste Verpackungsfunktion, um Schäden an Erzeugnissen zu verhindern und einem Lebensmittelverderb vorzubeugen. Innovationen, der Einsatz neuer Werkstoffe und Technologien sowie eine ökologische Gestaltung der Verpackungssysteme sprechen für einen Umbruch in der Verpackungsindustrie. Neue Verpackungen sollen ressourcenschonend und kreislaufwirtschaftsfähig gestaltet sein. Bestehende Verpackungs-systeme werden auf ihren Nutzen und ihre Effektivität überdacht. Die vorliegende Arbeit beschäftigt sich einerseits mit der Frage, ob Streifenkaugummis in der Aluminium-verbundverpackung noch gerecht verpackt sind oder ob Kunststoff beziehungsweise Glas einen besseren Schutz bieten. Dafür wurden Kaugummiproben in der Originalverpackung, einer bi-orientierten Polypropylen (BOPP) -Folie und einem Glasbehälter für drei beziehungsweise sechs Wochen im Klimaschrank bei 45°C, 30 % r.F. und 50 % Umluft gelagert. Nach drei und sechs Wochen wurden Proband*innen (n = 15; n = 7) zur Kaugummiverkostung geladen, um Kaugummiproben auf Unterschiede im Aussehen und Geschmack/Mundgefühl zu bewerten. Bei der Auswertung hat sich herausgestellt, dass die einzelnen Kategorien Aussehen und Geschmack/Mundgefühl einen signifikanten Unterschied aufweisen, was zu der Annahme führt, dass ein Unterschied zwischen den drei verschiedenen Verpackungsproben mit einer Wahrscheinlichkeit von 1/3 besteht. Die Aspekte Aussehen und Geschmack/Mundgefühl ergaben insgesamt keinen signifikanten Unterschied. Deshalb sind Rückschlüsse darauf, ob und welche Verpackung im Lagertest am besten abgeschnitten hat, nicht erlaubt. Zusätzlich wurden sowohl die originalen Kaugummiverpackungen als auch die zwei alternativen Verpackungsvarianten einer Nachhaltigkeitsbewertung unterzogen. Der Fokus lag dabei auf der Recyclingfähigkeit der vorliegenden Verpackungssysteme, wobei keine der Verpackungen mit einer guten Recyclingbilanz ausgestiegen ist. Das Ergebnis ist mit Bedacht anzunehmen, da die Verpackungsalternativen als Probematerialien ohne Distributionsmerkmale, beispielsweise einer Bedruckung, bewertet wurden. Die genauen Veränderungen der Kaugummiproben und die detaillierten Unterschiede zwischen den jeweiligen Verpackungen sind Teil zusätzlicher, empirischer Forschung, sowie eine ganzheitliche Nachhaltigkeitsbetrachtung erst Aufschluss über die umweltfreundlichste Verpackung geben könnte. Product protection is considered as the most important packaging function to prevent damage to products and food spoilage. Innovations, the use of new materials and technologies as well as an ecological design of packaging systems speak for a radical change in the packaging industry. New packaging should be designed in a resource-saving and circular economy way, existing packaging systems are reconsidered with regard to their usefulness and effectiveness. On the one hand, this paper deals with the question of whether strip chewing gum is still fairly packaged in aluminium composite packaging or whether plastic or glass offers better protection. For this purpose, chewing gum samples were stored in the original packaging, a bi-oriented polypropylene (BOPP) film and a glass container for three and six weeks in a climatic chamber at 45°C, 30% RH and 50% circulating air. After three and six weeks, subjects (n = 15; n = 7) were invited to chew gum tasting to evaluate chewing gum samples for differences in appearance and taste/mouthfeel. The evaluation revealed that the individual categories of appearance and taste/mouthfeel showed a significant difference, leading to the assumption that a difference between the three different packaging samples exists with a probability of 1/3. When added together, the appearance and taste/mouthfeel aspects did not show a significant difference. Therefore, conclusions as to whether and which packaging performed best in the storage test are not permitted. In addition, both the original chewing gum packaging and the two alternative packaging variants were subjected to a sustainability assessment. The focus was on the recyclability of the packaging systems, in which none of the packaging was able to show a good recyclability balance. The result must be accepted with caution, since the packaging alternatives were evaluated as sample materials without distribution features, such as printing. The exact changes in the chewing gum samples and the detailed differences between the respective packaging are part of additional, empirical research, just as a holistic sustainability assessment could provide information about the most environmentally friendly packaging.

Diese Arbeit beschäftigt sich mit der mikrobiellen und sensorischen Untersuchung dreier Convenience-Produkte aus Kräuterseitlingen (Pleurotus eryngii) eines ober-österreichischen Lebensmittelunternehmens. Die Anschaffung einer neuen Verpackungsanlage und ein damit neu etabliertes Verpackungssystem (Schutzgas-Gemisch und Tiefziehfolie) erfordert eine erneute Gewährleistung der Qualität der Produkte über eine Lagerungsdauer von 30 Tagen. Überprüft wurden die Proben an drei Untersuchungstagen bei einer Lagerungstemperatur von 7 und 12 °C mithilfe von Lagertests auf verschiedenen Agar-Platten. Die Lagerungsdauer und -temperatur hatten Einfluss auf die Qualität, ebenso Faktoren wie die Produktgruppe, Verpackungstag und Versuchszyklus. Aufschlussreiche Ergebnisse für den Betrieb wurden erzielt und Maßnahmen konnten umgehend umgesetzt werden, um die Qualität weiterhin zu verbessern. This thesis deals with the microbial and sensory examination of three convenience-products, made of King Oyster Mushrooms (Pleurotus eryngii), by an Upper Austrian food manufactory. Due to a new packaging machine and therefore a new established packaging method, with protective gases and a thermoforming film, the products` quality must be guaranteed once again. A storage period of 30 days and storage temperatures of 7 and 12 °C were examined on different agar plates. The quality of the products was influenced by the storage period and temperature, as well as by multiple factors like product group, packing day and trial cycle. Insightful results were achieved, which lead the processing to immediately take measures to improve the quality further.

The temperature dependence of device degradation of AlGaN/GaN HEMTs on SiC substrate with a gate length of 0.25 μm has been investigated. The critical surface temperature, where device degradation sets in has been determined using drain-current step-stress tests in combination with infrared microscopy. Using this fast reliability test, devices with different passivation technologies have been compared and, by optimizing the passivation technology, the critical temperature at which degradation of the threshold voltage begins has been improved from 310 °C to above 330 °C. Storage tests at 300 °C in nitrogen atmosphere confirm the improvement in high temperature stability. Physical failure analysis using electroluminescence and TEM/EDX cross-section revealed void formation and Au-diffusion at the gate as the main degradation mechanisms of devices with the conventional passivation technology.

Poly(lactic acid) (PLA) is a biodegradable and renewable polyester, which is considered as the most promising eco-friendly substitute of conventional plastics. It is mainly used for food packaging applications, but some drawbacks still reduce its applications. On the one hand, its low barrier performance to gases (e.g. O2 and CO2) limits its use for applications requiring low gas transfer, such as modified atmosphere packaging (MAP) or for carbonate beverage packaging. On the other hand, its natural water sensitivity, which contributes to its biodegradation, limits its use for high moisture foods with long shelf life.Other biopolymers such as wheat gluten (WG) can be considered as interesting materials able to increase the PLA performances. WG is much more water sensitive, but it displays better gas barrier properties in dry surroundings. This complementarity in barrier performances drove us to study the development of multilayer complexes PLA-WG-PLA and to open unexplored application scenarios for these biopolymers.This project was thus intended to better understand how food components and use conditions could affect the performances of PLA films, and how these performances could be optimized by additional processing such as surface modifications (e.g. corona treatment and coatings).To that aim, three objectives were targeted:-To study the stability of industrially scale produced PLA films in contact with different molecules (CO2 and water) and in contact with vapour or liquid phases, with different pH, in order to mimic a wide range of food packaging applications.-To better understand the impact of some industrial processes such as corona or hot press treatments on PLA.-To combine PLA with WG layer to produce high barrier and biodegradable complexes.Different approaches coming from food engineering and material engineering were adopted. PLA films were produced at industrial scale by Taghleef Industries with specific surface treatments like corona. Wheat gluten films, coatings and layers were developed and optimized at lab scale as well as the 3-layers PLA-WG-PLA complexes. Different technologies able to mimic industrial processes were considered such as hot press, high pressure homogenization, ultrasounds, wet casting and spin coating. The physical and chemical properties of PLA films were then studied at the bulk and surface levels, from macroscopic to nanometer scale. The functional properties like permeability to gases (e.g. O2 and CO2) and water, gas and vapour sorption, mechanical and surface properties were also investigated.Exposed to CO2, PLA films exhibited a linear sorption behaviour with pressure, but the physical modifications induced by high pressure did not affect its use for food packaging. However, when exposed to moisture in both liquid and vapour state (i.e. environments from 50 to 100 % relative humidity (RH)), PLA was significantly degraded after two months at 50 °C (accelerated test) due to hydrolysis. This chemical deterioration was evidenced by a significant decrease of the molecular weight, which consequently induced a loss of transparency and an increase of the crystallinity. The hydrolysis was accelerated when the chemical potential of water was increased, and it was surprisingly higher for vapour compared to liquid state. In addition, pH did not affect the rate of hydrolysis.Knowing much better the limitation of PLA films, the challenge was to improve its functional properties by combining them with WG, as a high gas barrier bio-sourced and biodegradable polymer. The use of high pressure homogenization produced homogeneous WG coatings, with improved performances. This process was thus selected for making 3 layer complexes by assembly of a wheat gluten layer between two layers of PLA, together with corona treatment and hot press technologies.Corona treatment applied to PLA physically and chemically modified its surface at the nanometer scale (...), Los materiales plásticos tradicionales son utilizados en todos los campos de nuestra vida y en particular modo como embajales de productos alimenticios; los cuales después de ser utilizados contaminan y dañan nuesto medio ambiente. Materiales plásticos derivados de recursos naturales y biodegradables, como el ácido poliláctico (PLA) se encuentran actualmente disponibles en el mercado a pesar de sus menores performances. Este proyecto de doctorado está orientado 1) al estudio de la estabilidad de películas de PLA bajo diferentes condiciones como temperatura, humedad relativa, pH o exposición a vapores o gases, 2) comprender los efectos en las propiedades de las películas de PLA de algunos procesos industriales como el tratamiento corona y hot press, 3) desarrollar complejos multicapas de PLA y gluten que tengan propiedades barrera mejores que las de las películas individuales.Los embalajes a base de PLA han sido producidos por Taghleef Industries, productor líder en el sector y dotado de las infraestructuras industriales adaptadas a los tratamientos superficiales como el tratamiento corona. Las películas de gluten y los coatings han sido desarrollados a escala de laboratorio, así como los complejos tricapa PLA-gluten-PLA.Las propiedades físicas y químicas de las películas de PLA han sido investigadas a nivel de superficie así como a nivel de bulk. Diferentes técnicas de análisis, frecuentemente utilizadas en los campos de las ciencias de los materiales y de las ciencias de los alimentos, han sido empleadas en este proyecto como calorimetría diferencial de barrido (DSC), análisis termogravimétrico (TGA), cromotagrafía de exclusión por tamaño (SEC), microscopía de fuerza atómica (AFM), microscopía electrónica de barrido (SEM), espectroscopía de infrarrojos por transformada de Fourier con reflectancia total atenuada (ATR-FTIR) y espectroscopía fotoelectrónica de rayos X (XPS).Las propiedades funcionales de los embalajes como las permeabilidades al vapor de agua, al oxígeno (O2), al dióxido de carbono (CO2) o al helio (He) han sido investigadas, asi como la absorción de gases/vapores, las propiedades mecánicas y las propiedades superficiales. A pesar de que las películas de PLA absorven linealmente CO2 a presiones mayores, la absorción del gas es reducida a bajas presiones y no modifica las propiedades físicas del PLA, como contrariamente sucede cuando el PLA es expuesto a altas presiones de CO2. Por lo tanto, su influencia en las propiedades funcionales del PLA es mínima en las normales aplicaciones alimentarias. De todos modos cuando los embalajes de PLA son expuestos a ambientes húmedos o cuando son sumergidos en agua, procesos de hidrólisis los degradan significativamente después de dos meses de conservación a 50 °C (test acelerado). Este deterioramiento químico ha sido evidenciado por una significativa reducción del peso molecular del PLA, que en consecuencia induce una pérdida de transparencia y un aumento de su cristalinidad. Además, se ha observado que el pH no influye en la velocidad de hidrólisis. Esta información tiene una importancia práctica para posibles usos del PLA como embalajes de alimentos a alta humedad. El gluten ha sido elegido por sus altas propiedades barrera cuando es protegido de ambientes a alta humedad. La incorporación de lípidos en las películas de gluten no han mejorado sus performances. Pero la tecnología de la homogenización a altas presiones ha permitido mejorar la dispersión del gluten, obteniendo películas más homogéneas y con mejores propiedades funcionales. Esta tecnología ha sido, por lo tanto, elegida para producir los complejos multicapa, intercalando las películas de gluten entre dos de PLA, utilizando el tratamiendo hot press (10 MPa, 130 °C, 10 min) (...), Les plastiques sont aujourd'hui des matériaux ubiquitaires utilisés dans tous les aspects de notre vie quotidienne, en particulier pour l'emballage alimentaire. Cependant, après usage, les plastiques sont une source de pollution de notre environnement naturel. Certains plastiques biodégradables et biosourcés sont déjà disponibles sur le marché, comme l’acide polylactique (PLA), mais ils présentent des performances inférieures. Ce travail de thèse vise à: 1) étudier la stabilité des films de PLA dans diverses conditions de température, d'humidité relative, de pH, d'exposition à des liquides ou à des vapeurs... 2) mieux comprendre l'impact de certains procédés industriels tels que les traitements corona ou pressage à chaud sur le PLA 3) combiner le PLA à des couches de gluten de blé afin de produire des complexes ayant des propriétés barrière plus élevées.Les films de PLA ont été produits par la société Taghleef Industries sur demande et avec des traitements de surface spécifiques, comme le traitement Corona. Des films et des enductions à basede gluten de blé ont été développés à l’échelle laboratoire ainsi que des complexes tricouches PLA- gluten-PLA. Les propriétés physiques et chimiques des films ont été étudiées par différentes techniques issues des sciences des matériaux et des aliments ont été utilisées, telles que l’analyse enthalpique différentielle (DSC), l'analyse thermogravimétrique (TGA), la chromatographie d'exclusion de taille (SEC), la microscopie de force atomique (AFM), la microscopie électronique (SEM), la spectroscopie infrarouge à transformée de Fourier (ATR-FTIR) et la spectroscopie de rayons X (XPS). Les propriétés fonctionnelles telles que la perméabilité à la vapeur d'eau, à l'oxygène (O2), au dioxyde de carbone (CO2) ou à l'hélium (He), la sorption de gaz et de vapeurs, les propriétés mécaniques et de surface ont également été étudiées.Exposés au CO2, les films de PLA présentent une isotherme de sorption linéaire avec l’augmentation de pression. Cependant les modifications physiques et chimiques induites à des pressions élevées n'affectent pas son utilisation dans le domaine d’application alimentaire. Au contraire, lorsque les films de PLA sont exposés à l'humidité à l'état liquide ou vapeur, leur dégradation survient après deux mois à 50 ° C (essai accéléré) suite à son hydrolyse. Cette détérioration chimique, mise en évidence par une diminution significative de la masse molaire, entraine une perte de transparence, mais également par une augmentation de la cristallinité. Par ailleurs, le pH n'affecte pas le taux d'hydrolyse, ce qui est d'un intérêt essentiel pour conditionner des aliments humides.Les films à base gluten de blé ont été choisis pour leurs propriétés de barrière élevées lorsque l’humidité relative reste faible. L'incorporation de lipides n'a pas apporté d'amélioration de leurs performances barrières. Cependant, l'utilisation d’un procédé d’homogénéisation à haute pression a permis une meilleure dispersion du gluten, ce qui a conduit à des films plus homogènes ayant ainsi de meilleures propriétés fonctionnelles. Ces conditions ont donc été retenues pour réaliser des complexes à 3 couches par assemblage d'une couche de gluten de blé entre deux couches de PLA en utilisant un pressage à chaud (10 MPa, 130 ° C, 10 min).La technologie de pressage à chaud montre une forte influence sur les films de PLA, de gluten et sur les tricouches. Elle induit une cristallisation accrue du PLA, ce qui augmente ses propriétés de barrière d'environ 40% et 60%, respectivement pour l'eau et l'oxygène. Cela masque par contre l’effet du traitement corona. D’autre part, le pressage à chaud induit une restructuration du réseau de gluten qui améliore les propriétés de barrière aux gaz des complexes, mais provoque aussi une évaporation de l'eau à l'interface gluten / PLA défavorable à l’adhésion des couches (...), I materiali plastici convenzionali trovano impiego in tutti campi della nostra vita, specialmente nel settore del packaging alimentare, ed in seguito all’utilizzo contaminano e danneggiano il nostro ecosistema. Materiali plastici derivanti da risorse naturali e biodegradabili, come acido polilattico (PLA), sono attualmente disponibili sul mercato anche se caratterizzati da performances inferiori.Questo progetto di dottorato è mirato 1) allo studio della stabilità di film di PLA a varie condizioni di stoccaggio come temperatura, umidità relativa, pH, o esposizione a vapori o gas; 2) a comprendere meglio le influenze di alcuni processi industriali come trattamento corona e hot press nelle proprietà dei film di PLA; 3) a sviluppare complessi multistrato tra film di PLA e di glutine che abbiano proprietà barriera più elevate rispetto ai singoli film.Gli imballaggi a base di PLA sono stati prodotti da Taghleef Industries, produttore leader nel settore e dotato di infrastrutture atte ai trattamenti di modificazione di superfice come il trattamento corona. I film a base di glutine e i coatings sono stati sviluppati e ottimizzati su scala di laboratorio, così come i complessi trilaminari PLA-glutine-PLA.Le proprietà fisiche e chimiche dei film di PLA sono state investigate a livello di superficie, così come a livello di bulk. Diverse tecniche analitiche, provenienti dal campo delle scienze dei materiali e delle scienze degli alimenti, sono state adottate in questo progetto di dottorato come calorimetria differenziale a scansione (DSC), termogravimetria (TGA), cromatografia di esclusione molecolare (SEC), microscopia a forza atomica (AFM), microscopia elettronica a scansione (SEM), spettrofotometria infrarossa a trasformata di Fourier in riflettanza totale attenuata (ATR-FTIR) e spettroscopia fotoelettronica a raggi X (XPS).Le proprietà funzionali come le permeabilità al vapore acqueo (H2O), all’ossigeno (O2), al diossido di carbonio (CO2) o all’elio (He) sono state investigate, cosi come l’assorbimento di gas e/o vapori, le proprietà meccaniche e le proprietà di superfice.Nonostante i film di PLA assorbano linearmente CO2 a pressioni crescenti, l’assorbimento di tale gas è ridotto a basse pressioni in modo da non modificare le sue proprietà fisiche – come contrariamente osservato quando il PLA è esposto a CO2 ad alte pressioni – e da non influenzare negativamente il suo utilizzo come imballaggio alimentare. Ad ogni modo, quando i film di PLA sono esposti ad ambienti umidi, o quando sono immersi in acqua liquida, sono significativamente degradati per idrolisi dopo due mesi di stoccaggio a 50 °C (test accelerato). Questo deterioramento chimico è stato evidenziato da una significativa riduzione del peso molecolare del PLA che, conseguentemente, induce una sua perdita di trasparenza e ne incrementa la sua cristallinità. Inoltre, è stato evidenziato che il pH non influenza la velocità di idrolisi. Quest’informazione ha importanza pratica per possibili utilizzi di PLA come imballaggio di alimenti ad alta umidità.Il glutine è stato scelto per le sue alte proprietà barriera, quando è protetto da ambienti ad alta umidità. Si è visto che l’incorporazione di lipidi non porta con sé grandi miglioramenti nelle performances dei film a base di glutine. Invece, l’utilizzo della tecnologia di omogeneizzazione ad alte pressioni permette una migliore dispersione del glutine, ottenendo film più omogenei e con migliori proprietà funzionali. Questa tecnologia è stata quindi scelta per produrre i complessi multistrato, intercalando i film di glutine tra due film di PLA, usando il trattamento hot press (10 MPa, 130 °C, 10 min). Si è osservato che il trattamento hot press modifica le proprietà dei film di PLA, di glutine e dei film multistrato Hot press induce cristallizzazione in PLA, e conseguentemente aumenta le sue proprietà barriera complessive, approssimativamente al 40 % all’acqua e al 60 % all’ossigeno (...)

International audience; Various types of food are now commercialized in packaging materials based on poly(lactic acid) (PLA) due to its eco-friendly nature. However, one of the main limitations related to PLA is its reactivity with water. For food applications, it is of critical importance to better understand the hydrolysis of PLA driven by water molecules either in liquid or in vapour state. This work focuses on the modifications of PLA induced by water when simulating contact with semi-dry foods (aw ≈ 0.5), high moisture foods (aw ≈ 1) and liquid foods (aw ≈ 1). This study undoubtedly shows that both the chemical potential of water and its physical state influence the hydrolytic degradation of PLA films. From a practical point of view, PLA packaging is very well suited for semi-dry foods, but is highly sensitive to high moisture and liquid foods.

Two studies (storage and challenge tests) investigated the microbial shelf life combined with a semi-quantitative determination of volatile compounds of cloudy apple juices after power ultrasound (US) treatment. The sublethal injury of spoiler yeasts (Candida parapsilosis and Rhodotorula glutinis) was also evaluated. The maximum effect of sonication was observed 14 days post-treatment in both tests, especially on psychrotrophic count. Sublethal injury occurred only in C. parapsilosis. Microbiological data estimated the shelf life of sonicated juices to be around 21 days. The typical aroma compounds of the raw juices decreased quickly in control samples compared with sonicated ones. The flavor stability provided by US treatment seemed to be maintained for at least the first 14 days of cold storage. The US affected the shelf life of raw apple juices, probably due to yeast sublethal stress; some specific aroma compounds could be used as freshness or treatment markers.

Nougat filled milk chocolates were stored at different temperatures to registrate the changes of their qualities. As a consequence of fat migration, triglyceride composition, melting properties, and solid fat contents of coating and filling were changed. After long-term storage fat bloom was developed on the chocolate surfaces. In parts I and II of the publication the influences of storage temperature on kinetics of lipid migration have been reported. Now, part III demonstrates the influence of storage temperature on bloom formation. Fat bloom on filled chocolates is started by fat migration and influenced by the crystallization tendency within the chocolate coating. The results are useful to improve shelf-life of filled chocolates and chocolate-coated bakery.