Glass Packages Research Articles

Si-Integrated Secondary Li-Ion Micro Batteries with Side-By-Side Electrodes for the Application As Buffers in Self-Sufficient Energy Harvesting Micro Systems

Lithium-ion cell chemistries, with their quite high energy densities, are naturally interesting candidates for the application as buffers in future self-sufficient energy-harvesting microelectronic systems [1, 2]. For these applications, thin film or 3D micro batteries could come into consideration [3, 4], although they might be comparatively expensive. Another promising approach that may limit production cost is the fabrication of micro batteries on a silicon wafer, where a vast number of batteries can be produced in one batch.Previously we have investigated a concept involving the integration of conventional stacked electrodes and a porous polymer separator in a silicon glass package [5]. In this study, a design with the anode and the cathode lying side by side, separated by a narrow silicon spacer, has been implemented. This design facilitates assembly and encapsulation considerably since no polymer separator is needed and both electrodes can be contacted from downside. Geometry can be adapted to meet balancing requirements for different electrode materials.Figure 1: Schematic profile of a battery with side-by-side electrode setup (arrows: paths of Li-ion movement)The production process for this kind of micro battery has been described in detail elsewhere [6]. Briefly, wet chemical etching of a Si-wafer of {110} crystal orientation is applied to form long and narrow cavities with vertical sidewalls at the long sides and a slope at the front sides. Such geometry ensures a good utilization of area (i.e. high specific capacity) at a high geometric accuracy as well as an easy contacting of the current collectors. The structured substrate is oxidized and passivated against Li-diffusion prior to the deposition of the active materials and the electrolyte by micro dispensing [7]. Finally, the device is almost hermetically sealed by the attachment of a glass lid (fig 1.).To obtain a high energy density, we have applied graphite as the anode material and nickel cobalt manganese oxide as the cathode material (LixC6 / Liy(Ni1/2Co1/5Mn3/10)O2). The fabricated single cells show a reproducible rate capability and cycling performance during continuous cycling between 4.1 and 3V (fig. 2). Due to the long paths for Li ion movement and the relatively thick electrodes the impedance of such cells is naturally higher as compared to cells with stacked electrodes. However, utilizing the special mechanical properties of silicon as a battery housing material it is possible to further decrease the width of the cavities for the electrodes (wcav) and the separator (wsep) substantially which is expected to result in improved rate capabilities. Furthermore, by fabricating cells with interdigital electrodes and narrow separators it is possible to enlarge the specific capacity per area, tailoring batteries for specific applications.The fabricated micro batteries have convential (i.e. non-thin-film) electrodes with a thickness in the range of around 50…150 µm. This is interesting for applications where a small volume, high capacity energy supply is needed. Examples are small energy autarkic sensors, e.g. implantable sensors for medical applications [8], or miniaturized sensor networks. Such applications are usually linked to radio modules for transmitting information. We can show that during pulsed discharge the system performance is less influenced by the relatively thick electrodes due to relaxation effects, resulting in higher extractable energies that are several times higher than during continuous discharge of the cells.Fig. 2: Cycling performance and rate capability of a cell with wcav=1.8mm, wsep=0.2mm, d1=0.15mm, d2=0.1mm The fabricated structures could be used in materials research, e.g. for high-throughput screening and in-operando electrode surface studies by applying different lid materials.REFERENCES[1] Belleville, M. et al., Energy autonomous sensor systems: Towards a ubiquitous sensor technology, Microelectronics Journal, 41, 11 (2010) pp. 740-745.[2] Hahn, R. Autonomous energy supply for electronic grains and wireless sensors, Frequenz, no. 3-4, pp. 87-91, 2004.[3] Hahn, R. und K. Marquardt, Secondary Microbatteries for Energy Harvesting Microsystems, In IDTEchEx Energy Harvesting Conference 2010 (Munich, Germany, 2010). May 26-27, 2010.[4] Hahn, R. Microbatteries for Energy Storage. In 4th SINANO device modeling summer school (Bertinoro, Italy, 2010). Jul. 19-23, 2010. [5] M. Thunman et al, Discharge Performance Dependence on Electrode Thickness for Li4Ti5O12/LiMn2O4 Cells for Application in Wafer-Integrated Microbatteries, ECS Trans. 2012 volume 41, issue 41, 147-157; doi: 10.1149/1.4717972.[6] K. Hoeppner et al., Design, Fabrication and Testing of Silicon-integrated Li-ion Secondary Micro Batteries with Side-by-Side Electrodes, Proceedings of PowerMEMS, London, 2013.[7] K. Hoeppner et al., Development and Investigation of Electrode Slurries for the Batch Fabrication of Li-ion Secondary Micro Batteries, EnMat Conference, 2013, Abstr. No 3276.[8] F. Albano et al., A fully integrated microbattery for an implantable microelectromechanical system, Journal of Power Sources, 185 (2008), pp. 1524–1532.

Irradiation Impact on the Leaching Behavior of HLW Glasses

Fission products and minor actinides arising from spent fuel reprocessing are immobilized in a borosilicate matrix known as high level nuclear waste glass (i.e. HLW glass). Glass packages are intended eventually for disposal in a geological repository. The long-term behavior of HLW glass subjected to radiation by long-life radionuclides must thus be investigated with respect to geological disposal. The present article focuses on HLW glass alteration under irradiation conditions by providing a general description of the methodology and illustrating it through examples. The scientific approach adopted to study irradiation potential effects combines experiments performed on radionuclide-doped borosilicate glasses and non radioactive glasses externally irradiated, focusing on all the different leaching stages (initial, drop and residual steps). Different parameters, such as the cumulative dose, the dose rate, the electronic and the ballistic impacts, are taken into account. As under disposal conditions the glass radioactivity will be quickly governed by alpha decay (after 300 years), the results presented here to illustrate the methodology concern the behavior of alpha-doped glasses. Concerning the initial alteration rate, both the alpha activity and the alpha cumulative dose have been studied and no significant effects have been observed. The structural variations observed on the irradiated solid are thus not important enough to induce any changes in the initial chemical reactivity between glass and water. Concerning the drop and residual alteration steps, the behavior of a 239Pu-doped glass having an alpha dose rate corresponding to a HLW glass after around 1500 years has shown no effect on the kinetics, nor on the altered layer morphology. Moreover, the plutonium appears to be highly retained in the alteration layer (∼ 95%).

Monitoring and modelling of headspace-gas concentration changes for shelf life control of a glass packaged perishable food

Gas concentrations in the headspace of hermetically sealed glass packages of seasoned soybean sprouts were monitored and related to their microbial quality, i.e., the change in aerobic bacterial count, in order to examine the potential for using package gas changes as a primary quality index for shelf life control. Aerobic bacterial count, CO2 and O2 concentrations were measured from packages stored at four different temperatures: 0, 5, 10 and 15 °C. The CO2 concentration increased and the O2 concentration decreased with microbial growth. The microbial growth and CO2 concentration change were described by a logistic function to yield kinetic parameters, and their temperature dependence was analysed by a square-root model. The kinetic parameters for microbial growth and CO2 production differed in their magnitude and temperature dependence. The lag time observed for the increase in CO2 concentration could be used as a shelf life index that corresponds to the time to reach a given microbial limit (here, 107 CFU/g) under different temperature conditions, particularly under conditions of temperature abuse.

Specific outcomes of the research on the radiation stability of the French nuclear glass towards alpha decay accumulation

This paper presents an overview of the main results of the French research on the long-term behavior of SON68 nuclear glass towards alpha decay accumulation. The effect of the radiation damage induced by alpha decay and also helium build-up were investigated by examining glass specimens, doped with a short-lived actinide 244Cm, irradiated by light and heavy ions. Additionally, atomistic simulations by molecular dynamics have provided further information on the atomic-scale effects of the macroscopic phenomena observed.These studies have shown that some macroscopic properties vary with the accumulation of alpha decay, but then stabilize after integrated doses of the order of 4×1018αg−1. For example, the glass density diminishes by about 0.6%, its Young’s modulus by about 15%, and its hardness by about 30%, while its fracture toughness increases by around 50%. The SEM and TEM characterization showed that the glass is still homogeneous. No phase separation, crystallization or bubbles formation was noticed up to an alpha decay dose corresponding to several thousand years of disposal of nuclear glass canister. Moreover the initial alteration rate of the glass is not significantly affected by the glass damage induced by alpha decays or heavy ions irradiations.The comparison of the macroscopic evolutions of the Cm doped glass with those obtained for glasses irradiated with light or heavy ions (from either experimental and molecular dynamic studies) suggests that the macroscopic evolutions are induced by the nuclear interactions induced by the recoil nuclei of alpha decay.The analysis of the behavior of the glass structure subjected to ballistic effects with various spectroscopic studies, together with the results of atomistic modeling by molecular dynamics, have identified some slight changes in the local order around some cations. Moreover a modification of the medium-range order has also been demonstrated through changes in the bond angles between network formers and broadening of the ring size distributions, indicating increasing disorder of the glass structure. This structural evolution induced by alpha decays would be driven by the reconstruction of the glass disorganized by displacement cascades of the recoil nuclei, freezing a glass structure with a higher fictive temperature. This “ballistic disordering (BD) fast quenching” event induces a new glassy state characterized by a higher enthalpy state. Accumulation of α decays induce similar phenomena of “BD-fast quenching”, increasing the fraction of the sample volume characterized by a “high enthalpy state”. At dose around 4×1018αg−1 the entire sample volume has been affected by “BD-fast quenching” events at least once, which explain the stabilization of the evolutions of glass structure and properties.Helium behavior was also studied by measuring the helium solubility constants and diffusion coefficients. Helium atoms are incorporated into the glass free volume with a solubility constant that varies less than 10% around a value of about 1011atcm−3Pa−1 and a density of solubility sites accessible for helium around 2×1021 sitescm−3 which is larger than helium production in a glass package. Helium diffusion experiments performed on infused and Cm doped SON68 glasses indicate that helium migration is controlled by a classical thermally activated diffusion process, whose activation energy (e.g. 0.6±0.03eV) is not affected by an alpha decay dose of around 1019αg−1.Helium implantation studies suggest that helium trapping could exist in nanometer size bubbles. SEM and TEM analysis performed on a Cm doped glass damaged by an alpha decay dose of around 1019αg−1, showed a homogeneous glass without crystallization, phase separation or bubbles with a spatial resolution limit of 10nm. Bubbles of significant size seem very unlikely to form at room temperatures. But, the ability to form helium bubbles of nanometer size, at temperature below the glass vitreous transition temperature cannot be excluded. However, all these studies agree on one point, the absence of macroscopic consequence on the glass integrity of accumulation of high helium concentration in the glass.

Simulation of cooling and solidification of three-dimensional bulk borosilicate glass: effect of structural relaxations

The modeling of the viscoelastic stress evolution and specific volume relaxation of a bulky glass cast is presented in this article and is applied to the experimental cooling process of an inactive nuclear waste vitrification process. The concerned borosilicate glass is solidified and cooled down to ambient temperature in a stainless steel canister, and the thermomechanical response of the package is simulated. There exists a deviant compression of the liquid core due to the large glass package compared to standard tempered glass plates. The stress load development of the glass cast is finally studied for different thermal load scenarios, where the cooling process parameters or the final cooldown rates were changed, and we found a great influence of the studied cooldown rates on the maximum stress buildup at ambient temperature.

Effect of Sulfites and Sorbates on the Preservation and Color of Pickled Blanched Garlic under Different Storage Conditions

The influence of sulfites and sorbates on the microbial stability and color of pickled blanched garlic stored under different conditions was studied. Two storage temperatures (ambient, 20–24C; refrigeration, 6–9C) and two types of packaging (glass bottle, plastic pouch consisting of polyester/polyethylene/saran) were considered. Both sulfites and sorbates gave satisfactory results as antimicrobial agents, even at room temperature. Sulfite was also effective as an anti-browning agent, but sorbate produced the opposite effect on color. The samples packed in plastic pouches stored at room temperature had the highest values of the parameters b* (yellowness), C (color purity) and browning index. The sorbate level hardly changed during storage, regardless of the storage conditions used, but the sulfite level decreased, especially in samples packed in plastic pouches stored at room temperature, in which oxidation to sulfate was demonstrated to be the sole mechanism of sulfite loss. Practical Applications Long-term preservation of pickled blanched garlic without the need for expensive preservation treatments such as pasteurization or refrigeration is possible with the help of sulfites and/or sorbates as preservatives. However, these preservatives yield opposite effects on garlic color. The data collected in this study demonstrated that sulfite at approximately 100 mg/L of SO2 at equilibrium was an effective antimicrobial and anti-browning agent. For practical purposes, we recommend the use of sulfites alone and glass packages to maintain the quality of pickled blanched garlic as the presence of sorbates and/or the use of plastic packages enhance browning reaction.

ДОСЛІДЖЕННЯ КОНТАКТНОЇ ВЗАЄМОДІЇ ЦИЛІНДРИЧНИХ ТІЛ НА ПОХИЛОМУ ТРАНСПОРТЕРІ У ФАРМАЦЕВТИЧНІЙ ТЕХНОЛОГІЇ

There was studied the percussive interaction of bodies rotation on transport lines of medicaments’ bottling on inclined conveyers. There were determined and substantiated the analytical dependences for finding out the maximum meanings of raprochement of different speeds of conveyer’s motion and glass packages type and size. There was shown that the typical time of determination of contact deformations by the statistic elasticity (Herts’ sum) is less than the typical time of interaction of glass packages, that confirms the usage correctness of statistic theory

Laser Assisted Frit Sealing for High Thermal Expansion Glasses

Analysis of laser assisted frit sealing processes for high CTE > 5x10 -6 /°C (coefficient of thermal expansion) glasses was done. The method is based on the thermal fusion of two glasses with a low melting point glass frit. This method is used when thermal sensitive materials such as OLED (organic light emissive device) are present in the glass package. The frit is selected to be highly absorbent at the sealing laser wavelength, while the glasses are transparent at the sealing wavelength. It was found that laser sealing of a high CTE glass with sealing conditions optimized for a low CTE (< 5x10 -6 /°C) glass, such as glass suitable for display devices, produces very poor results. The issue with sealing glasses with high CTE is high transient stress formed during heating and cooling the glass to the sealing temperatures. The sealing yield of high CTE glasses could be significantly improved by increasing “residential heating time” by reducing sealing speed or increasing laser spot size. This results in lower cooling rate of the glass and helps to reduce the residual stress. This was confirmed by stress analysis showing a reduction of the stress for soda lime glass with increasing residential heating time.

Thermal properties of organic light-emitting diodes

Thermal management is important for the efficient operation of organic light-emitting diodes (OLED, or PHOLED) at high brightness, with the device operating temperature influencing both lifetime and performance. We apply a transmission-matrix approach to analytically model the effects of thermal conduction, convection and radiation on OLED temperature. The model predictions match experiment without requiring the use of fitting parameters. This allows for the simulation of the thermal response of various device architectures, materials combinations and environmental factors under a variety of operating conditions. Using these simulations, we find that 87% of the heat is dissipated through the air space adjacent to the glass package cap. Furthermore, an air gap between the device cathode and cap provides a significant thermal impedance. Minimizing the thickness of the internal air gap can lead to nearly room temperature operation, even at very high brightness.

Investigation of the use of Solderjet Bumping for joining the thinwalled glass package of a complex mechatronic lens implant

Article Investigation of the use of Solderjet Bumping for joining the thinwalled glass package of a complex mechatronic lens implant was published on September 6, 2012 in the journal Biomedical Engineering / Biomedizinische Technik (volume 57, issue SI-1-Track-S).

Viscous Hot Glass Forming for Optical Wafer Level Packaging of Micro Mirrors

Abstract MEMS mirrors are gaining considerable interest for consumer applications like embedded pico projectors in smartphones. The use of micro mirrors in mobile systems demands for a robust package that prevents the system from contamination by particles, gases or fluids. Appropriate optical packaging so far has been neglected in most published MEMS mirror developments. This paper describes a unique technology to fabricate glass packages on 8 inch wafers with inclined optical windows for MOEMS on wafer scale which avoids the occurrence of highly intense reflections of the incident laser beam in the projected images. The new viscous glass forming process enables the fabrication of glass devices with optical windows with oblique surfaces using bonded silicon-glass wafers.

Armazenamento de sementes de Erythrina velutina willd

O trabalho teve como objetivo avaliar o efeito de diferentes embalagens e ambientes de armazenamento na manutenção da qualidade fisiológica de sementes de Erythrina velutina Willd.. O experimento foi conduzido no Laboratório de Análise de Sementes do Departamento de Fitotecnia do Centro de Ciências Agrárias da Universidade Federal da Paraíba (CCA-UFPB), localizado no município de Areia (PB). As sementes de Erythrina velutina Willd. foram coletadas embaixo de árvores matrizes, no mesmo município e levadas para o laboratório, onde se realizou a homogeneização e acondicionamento em embalagens de papel, pano e vidro e, posterior armazenamento em condições não controladas de laboratório (±25ºC), geladeira (6 ± 2ºC) e câmara fria (4 ± 2ºC), por um período de 225 dias. Antes e após os intervalos de 45 dias foram retiradas amostras de cada embalagem e ambiente de armazenamento para avaliação das seguintes características: teor de água, emergência (porcentagem e índice de velocidade), comprimento e massa seca de epicótilo, hipocótilo e raiz das plântulas normais. O delineamento experimental utilizado foi inteiramente ao acaso com quatro repetições de 25 sementes para cada teste. As sementes de mulungu são ortodoxas e acondicionando-as nas embalagens de papel, pano ou vidro podem ser armazenadas nos ambientes de laboratório, geladeira e câmara fria, durante 225 dias sem perdas significativas na emergência das plântulas.

Helium diffusion in curium-doped borosilicate waste glass

The isothermal release of helium from 244Cm-doped borosilicate glass has been studied as a function of time at different annealing temperatures. Helium measurements were performed using a micro gas chromatograph coupled to a furnace installed in a hot cell at ATALANTE nuclear research facility. Plane-parallel glass samples were prepared from glass discs that had been stored for 5.1 years at room temperature, accumulating around 10 19 alpha decays per gram of glass, a level that will be reached in current nuclear glass packages several thousand years after disposal. The experimental helium release data were simulated using a 3D numerical model to determine the helium diffusion coefficients. The extracted diffusion coefficients follow the Arrhenius law with an activation energy of 0.61 ± 0.03 eV and a pre-exponential factor of (5.7 ± 1.6) × 10 −3 cm 2 s −1. The results were compared with literature data on damaged and undamaged glasses to assess the effect of glass damage on helium release. The helium release results are consistent with a thermal diffusion mechanism involving only one population of helium atoms. The helium diffusion coefficients were unaffected by the glass alpha damage.

Semi-stochastic generator (FraGMA) of 2D fractured media by mechanistic analogy – Application to reactive transport in a fractured package of vitrified nuclear waste

In a geological storage context, the durability of nuclear glass is first and foremost determined by its alteration rate and by the surface being leached. This surface is comprised of a network of three-dimensional cracks due to the stress relief generated by the cooling of glass packages. In order to improve the methods employed so far for quantifying the impact of a fissure network on the life time of glass packages in geological disposal, we have developed a software, referred to as FraGMA, which can be used to generate a realistic 2D geometry of the fissure network inside the glass based on mechanistic analogies. This type of tool is required for providing a mesh adapted to the calculation codes simulating water flow and glass alteration in such a medium. The main principles of this tool have been developed and its parameters have been defined based on the analysis of theoretical fracture processes and observations of real fissure networks. The 2D networks developed using FraGMA are compared with cross-sections of real networks. It is outlined that the general structure of the fracture maps is correctly reproduced, compared to the observations; consequently, it is relevant to apply the tool for further studies in order to generate more complex crack networks, and to study the channeling in such structures, as expected by the strong organized pattern of the experimental fracture maps.

Kapselung eines mechatronischen Systems zur Wiederherstellung der Akkommodationsfähigkeit

In order to restore the ability of accommodation of the human eye, a lens implant manufactured by micro system technology can be used. This highly integrated Artificial Accommodation System contains sensitive electronics as well as moving components in order to adapt its refractive power. One challenge of the production of this system is the encapsulation. It has to be a biocompatible and long-term reliable package. In this paper the advantages of a hermetic glass package over other approaches of encapsulation are introduced. Concepts of production for a glass package are presented. The package is thereby optimised to be placed in the optical path of the eye, but it can also be used for the encapsulation of other implants.

Analytic implementation of the GRAAL model: Application to a R7T7-type glass package in a geological disposal environment

The Glass Reactivity with Allowance for the Alteration Layer Model (GRAAL) was proposed in 2008 to describe borosilicate nuclear glass alteration based on coupling an affinity law with the formation and dissolution of a passivating reactive interface. It is examined here in a simplified form in which only the affinity with respect to silicon is taken into account with a concentration at saturation C sat, and the precipitation of neoformed phases is described by an affine relation for silicon above a precipitation threshold C sat ′ . This simplified “analytical GRAAL” model is capable of predicting the quantities of altered glass and the silicon and boron concentration variations in analytical or semi-analytical form, and thereby identify the main characteristic quantities of the system. The model was tested against a series of laboratory experiments lasting from a few days to a few years; its sensitivity to the parameter values was examined, and the model was validated with respect to SON68 glass alteration in initially pure water. It was then applied to the alteration of a glass package in a repository over periods of up to a million years, by means of exploratory calculations comprising a sensitivity study of the internal model parameters and extrapolation to the temperatures expected in a geological repository in order to identify the parameters and mechanisms having the greatest impact on the residual alteration rate. Alteration is controlled by the precipitation of neoformed phases in every case. The transient conditions are of very limited duration with respect to either silicon or boron (no more than a 100 years, with less than 0.01% alteration of the package). In the precipitation law used in the model, the residual alteration rate and total package lifetime are determined primarily by two parameters: k′ (the precipitation kinetics) and σ′ (the precipitate surface area per unit volume in the geological barrier). The package lifetime is about 3 × 10 5 years at 30 °C assuming a reasonable value for σ′ (10 6 m −1), and would be increased by a factor 3–6 if precipitation in the barrier were disregarded. This cursory description of precipitation will be validated and refined through specific laboratory tests at 50 °C and lower temperatures, coordinated with the development of the “geochemical GRAAL” model and with integral tests in contact with clay and canister corrosion products.

Determination of Nutritive Values of Jamun Fruit (Eugenia jambolana) Products

Study on the nutritive values of stored Jamun (Eugenia jambolana) products, namely jam, squash, ready-to-drink juice, seed powder and pulp powder was carried out at the Institute of Food Sciences and Technology, Sindh Agriculture University Tandojam. The specific fruit cultivar undertaken for this scientific evaluation was commonly known as (Improved) variety of Jamun. Besides of jam, squash and juice products, Jamun seed and pulp powder also have good nutritive values and were quite rich in carbohydrates accompanied by enough protein, ash, crude fibers but were not sufficient in fat composition. It was observed that nutritional values were varied at different packaging and storage temperature. The glass package among the packages and refrigerator temperature among the storage temperatures showed good results in terms of retaining good quality nutritive values and extensive shelf life of the products. The results were statistically significant. This study could be a beneficial source to the dieticians/nutritionist to consider Jamun as best nutraceutical fruit with natural curing and food industries for manufacturing commercially viable food products.

Determination of the correlation between physical measurements of roughness, optical properties, and perception of frosted glass surfaces

Chemical frosting is used as a surface decorating method by many glass package producers. After immersion in an acid frosting bath, glass items present the desired frosted effect. The perception of this particular effect is due to the formation of a microscopic crystalline pattern on the glass surface, which scatters light passing through the glass surface. The chemical composition of the frosting bath influences these properties by modifying the surface roughness, the depth, and the average slopes of the crystalline pattern. Perception of the final aspect can be modified according to the chemical composition of the frosting bath. Different correlations between all these parameters exist and have been quantified.

Driver IC and COG Package Design

This paper investigates the interconnection between the driver integrated circuit (IC) and glass substrate via anisotropic conductive adhesive (ACF) of chip on glass package. The conductive particle deformation is evaluated using a novel method, optical microscope (OM) inspection. The proposed method is more convenient than the traditional approach using scanning electron microscopy applied in the manufacturing process. Interconnection performance is easily judged using OM, allowing poor interconnection between the driver IC and glass substrate to be screened out. Several types of driver ICs with different bump area ratios (total input bump area/total output bump area, input/output ratio) and length/width (L/W) ratios are designed in this experiment. The conductive particle deformations are investigated in this study. Driver ICs with L/W ratios larger than 15 have better conductive particle deformation uniformity at each position. The average deformation degree at the driver IC center position is larger than that at the side and edge positions. The deformation degree at the input position with a smaller bump area is better than that at the output position. The conductive resistance increases with the reliability testing time because of the thermal stress effect and softening of the ACF polymer material. The deformation degree is related to the conductive resistance of the interconnection. The conductive resistance is lower at the center and input positions with larger deformation degree.

Mold challenge study in bottled natural mineral waters and spring waters

Microbiological challenge study was carried out to verify the microbial stability of bottled waters against four different mold species isolated from bottled water (Fusarium sp.; Cladosporium sp.; Penicillium chrysogenum and Aspergillus fumigatus) and to follow the growth of the molds in bottled water. Twelve types of bottled water with different mineralization and CO2 level in PET and glass packages were collected from 4 European countries. Three different inoculation levels of spore suspensions were used to contaminate bottled water samples. The surviving colony forming unit (CFU) numbers and visual growth were monitored during the investigation period (26 weeks). The results of surviving CFU showed that the fungal growth is mostly determined by the carbonation level and the type of the mold strain. Neither the inoculation level nor the mineral content had any significant effect on the survival of the different mold strains. Results showed decreased CFU numbers in carbonated waters, while slow decreasing, stagnation or even some growth in still waters. A. fumigatus was the most resistant test species. None of the other tested mold strains survived the first 12-week test period in carbonated water. Visual growth was not detected in carbonated water samples, in contrast to all of the non-carbonated samples.