Smartphone-based food diagnostic technologies: A review

A new generation of mobile sensing approaches offers significant advantages over traditional platforms in terms of test speed, control, low cost, ease-of-operation, and data management, and requires minimal equipment and user involvement. The marriage of novel sensing technologies with cellphones enables the development of powerful lab-on-smartphone platforms for many important applications including medical diagnosis, environmental monitoring, and food safety analysis. This paper reviews the recent advancements and developments in the field of smartphone-based food diagnostic technologies, with an emphasis on custom modules to enhance smartphone sensing capabilities. These devices typically comprise multiple components such as detectors, sample processors, disposable chips, batteries and software, which are integrated with a commercial smartphone. One of the most important aspects of developing these systems is the integration of these components onto a compact and lightweight platform that requires minimal power. To date, researchers have demonstrated several promising approaches employing various sensing techniques and device configurations. We aim to provide a systematic classification according to the detection strategy, providing a critical discussion of strengths and weaknesses. We have also extended the analysis to the food scanning devices that are increasingly populating the Internet of Things (IoT) market, demonstrating how this field is indeed promising, as the research outputs are quickly capitalized on new start-up companies

Sensory quality control of alcoholic beverages using fast chemical sensors

Control de calidad sensorial de bebidas alcohólicas utilizando rápidos sensores químicosEn la presente tesis Doctoral, han sido aplicados dos sensores artificiales para el análisis debebidas alcohólicas: la nariz electrónica basada en la espectrometría de masas (MS) y la lenguaelectrónica basada en la espectroscopía infrarroja con transformada de Fourier (FTIR). Elpropósito fue desarrollar nuevas estrategias para analizar la autenticidad de estos productos,desde un punto de vista sensorial, por medio de técnicas las espectrales antes mencionadas.Adicionalmente, ha sido utilizado un espectrofotómetro UV-visible como ojo electrónico. Eltrabajo presentado pretende ser un avance significativo hacia el desarrollo de un catadorelectrónico mediante la fusión de los tres sensores químicos: nariz electrónica, lenguaelectrónica y ojo electrónico.Sensory quality control of alcoholic beverages using fast chemical sensorsIn the present Doctoral Thesis, two chemical artificial sensors are applied to the analysis ofalcoholic beverages: the Mass Spectrometry (MS)-based electronic-noses and Fouriertransform infrared (FTIR)-based electronic-tongue. The aim was developing new strategies totest the authenticity of these products, from a sensory point of view, by means of the spectraltechniques above mentioned. Additionally, has been used an UV-visible spectrophotometer aselectronic eye. The work presented wants to be a significant advance towards the developmentof an electronic taster through the fusion of three chemical sensors: electronic nose, electronictongue and electronic eye

Potential use of electronic noses, electronic tongues and biosensors, as multisensor systems for spoilage examination in foods

Development and use of reliable and precise detecting systems in the food supply chain must be taken into account to ensure the maximum level of food safety and quality for consumers. Spoilage is a challenging concern in food safety considerations as it is a threat to public health and is seriously considered in food hygiene issues accordingly. Although some procedures and detection methods are already available for the determination ofspoilage in food products, these traditional methods have some limitations and drawbacks as they are time-consuming,labour intensive and relatively expensive. Therefore, there is an urgent need for the development of rapid, reliable, precise and non-expensive systems to be used in the food supply and production chain as monitoring devices to detect metabolic alterations in foodstuff. Attention to instrumental detection systems such as electronic noses, electronic tongues and biosensors coupled with chemometric approaches has greatly increased because they have been demonstrated as a promising alternative for the purpose of detecting and monitoring food spoilage. This paper mainly focuses on the recent developments and the application of such multisensor systems in the food industry. Furthermore, the most traditionally methods for food spoilage detection are introduced in this context as well. The challenges and future trends of the potential use of the systems are also discussed. Based on the published literature, encouraging reports demonstrate that such systems are indeed the most promising candidates for the detection and monitoring of spoilage microorganisms in different foodstuff

Hybrid Electronic Tongues Applied to the Quality Control of Wines

The legislation of food industry is becoming increasingly strict with regard to the quality of food products. Therefore, the market is demanding for automatic systems of analysis that allow fast and accurate monitoring of the evolution of quality parameters in agrofood products or permit obtaining information to optimize production processes. In this context, sensors and more specifically microsensors play an important role since they allow fast and reproducible measurement of a large number of quality parameters with good reliability and can be implemented in portable systems. This paper presents a review of the results obtained with an electronic tongue based on different kinds of microsensors applied to wine analysis by the team of IMB-CNM. This multisensor system allows on one hand classifying the wine according to its features like grape variety, geographic origin, year, and organoleptic characteristics and on the other hand quantifying some parameters of interest in quality control, such as alcoholic degree, pH, ions, total acidity, glycerol, and color

Advancements in microfabricated gas sensors and microanalytical tools for the sensitive and selective detection of odors

In recent years, advancements in micromachining techniques and nanomaterials have enabled the fabrication of highly sensitive devices for the detection of odorous species. Recent efforts done in the miniaturization of gas sensors have contributed to obtain increasingly compact and portable devices. Besides, the implementation of new nanomaterials in the active layer of these devices is helping to optimize their performance and increase their sensitivity close to humans’ olfactory system. Nonetheless, a common concern of general-purpose gas sensors is their lack of selectivity towards multiple analytes. In recent years, advancements in microfabrication techniques and microfluidics have contributed to create new microanalytical tools, which represent a very good alternative to conventional analytical devices and sensor-array systems for the selective detection of odors. Hence, this paper presents a general overview of the recent advancements in microfabricated gas sensors and microanalytical devices for the sensitive and selective detection of volatile organic compounds (VOCs). The working principle of these devices, design requirements, implementation techniques, and the key parameters to optimize their performance are evaluated in this paper. The authors of this work intend to show the potential of combining both solutions in the creation of highly compact, low-cost, and easy-to-deploy platforms for odor monitoringPostprint (published version

Review—Lab-in-a-Mouth and Advanced Point-of-Care Sensing Systems: Detecting Bioinformation from the Oral Cavity and Saliva

Cavitas sensors and point-of-need sensors capable of providing physical and biochemical information from the oral cavity and saliva have attracted great attention because they offer remarkable advantages for noninvasive sensing systems. Herein, we introduce the basic anatomy and physiology of important body cavities to understand their characteristics as it is a pivotal foundation for the successful development of in-mouth devices. Next, the advanced development in lab-in-a-mouth sensors and point-of-need sensors for analyzing saliva are explained. In addition, we discuss the integrations of artificial intelligence and electronic technologies in smart sensing networks for healthcare systems. This review ends with a discussion of the challenges, future research trends, and opportunities in relevant disciplines. Mouthguard-based sensors and conventional salivary sensing devices will continue to be significant for the progress in the next-generation sensing technologies and smart healthcare systems.ope

Plasmonic nanostructures for molecular sensing and colour filtering

Plasmonic nanoarrays offer a number of advantages over other technologies when it comes to optical sensing and colour filtering—namely their full tunability across the visible spectrum, high sensitivity to local refractive index changes, relative stability, and ultra-high resolution. For optical sensors, as their use progresses towards portable devices capable of rapid and highly-specific sensing, reduction in complexity, device size, and data acquisition time is key; and for optical colour filtering and encoding, the desire for long-term-stability and ultra-high resolution is key. One way to achieve the aforementioned goals in both fields is through the development of optical devices capable of producing two signals/displays within one region. This thesis explores the fabrication and characterisation of such devices for applications in molecular sensing and colour display technologies. First, a proof-of-concept device consisting of two nanoplasmonic arrays arranged in a multilayer configuration is explored. This device is demonstrated capable of self-correcting for drift by simultaneously obtaining both sensing and reference signals from a single measurement without complex optics or multiple sensing regions. This is design holds promise for point-of-care diagnostics, where data acquisition occurs over extended periods of time and measurement stability due to the external environment may be problematic. Next, another method of arranging two plasmonic nanoarrays is examined. These devices consist of superimposed aluminium and gold nanoarrays with modified surface chemistries resulting in a bimetallic device which produces two distinct resonance peaks for each sensing region. When combined, the signals from the different arrays are demonstrated capable of discriminating between organic solvents and between whiskies using trained pattern recognition. As each element in the bimetallic optical tongue produces two partially-selective measurements (rather than the one measurement capable with comparable devices), the proposed sensor is capable of halving device size and data-acquisition time. This advance in miniaturisation and multiplexed readout would be highly useful in areas that rely on assays for determining if a mixture is within tolerance, such as the medical, food & drug, and security industries. Then, a new approach to high-density image encoding is demonstrated using full-colour, dual-state nano-pixels, doubling the amount of information that can be stored in a unit area. The smallest readable ‘unit’ using a standard optical microscope relates to 370 nm x 370 nm. As a result, dual-state nano-pixels may prove significant for long-term, high-resolution optical image encoding, and counterfeit-prevention measures. Finally, a combination of plasmonic sensing with the dual-state capabilities of the nano-pixel design presented is investigated. The dual-state capabilities of the nano-pixel design will allow trapping of biomolecules with one arm while simultaneously, yet independently, sensing with the other. While only preliminary work is covered, once successfully developed, such devices will aid the understanding of proteins and thus benefit the fields of biology, chemistry, medicine, and pharmacy. Additionally, they will allow for the testing and creation of new disease screenings and drug therapies

Innovative Strategies to Control Oxidation in Wine

The topic of wine oxidation and the need of innovative strategies to prevent its extent were the subject of this PhD thesis. The complexity of the oxidative chemical reactions occurring in wine during its conservation were highlighted, and multiple analytical approaches were used to provide a more comprehensive understanding of wine oxidation and to plan tailored strategies to avoid its occurrence. The complexity of wine oxidation could be in a simplified manner attributed to the following main factors: wine composition, storage conditions, and oxygen exposure. An integrated theoretical and experimental approach was used, including study of chemical, physical and technological variables involved in wine production and storage. Standard protocols currently used to analyse the wine composition were implemented, if needed, and the lab scale trials were coupled with monitoring real case study along the supply chain. In particular, the effectiveness of plant extracts (tannins) commonly used in oenology was also evaluate in order to better understand their antioxidant properties and to encourage an harmonized regulation of their use in winemaking. The information provided and the scientific approach proposed in this thesis work may be useful in future work aimed to study practical implications and effective strategies to control oxidation in wine

Impact of oxygen on quality of white wine

Today?s wine market is becoming more and more saturated. At given conditions, the understanding of the consumer needs and preferences determines the success of a wine producer. The value of white and rosé wines appreciated by the consumers lies in their fruity and fresh character. Wine oxidation is one of the major wine failures. Recently, it has been reported that up to 48% of the wines rated as faulty by judges in wine competitions exhibited off-flavours that can be linked to the erroneous management of oxygen. Wine exposure to oxygen is possible throughout the whole winemaking process and depends on process conditions and applied equipment. Oxygen can be dissolved in wine up to 8.8 mg/L at normal conditions. After dissolution, oxygen concentration in liquid phase is normally decreasing to undetectable content due to chemical reactions of molecular oxygen with other wine constituents. Wine oxidation is a complex process. The effects may vary significantly influenced by numerous factors, including a type of wine, operation, oxygen amount chemical composition of wine, pH, storage temperature, light exposure, metal content and redox state of wine. Oxygen has a potential to support positively, and subsequently to ruin aroma and colour of wine. Most white wines are negatively affected by small amounts of dissolved oxygen provoking rapid aroma loss and oxidative browning, thus decreasing attractiveness for consumers, whereas in red wines microoxygenation may help to stabilise wine colour and remove reductive off-flavours. Up to now, most of the research on wine oxidation was focused on experiments in model solutions. Although these studies deliver valuable information about oxidation mechanisms, there was, however, limited data published on real wine experiments linking analytical data and sensory analysis. Consequently, the background of the present investigations was comprehensive evaluation of the effectiveness of the various factors influencing wine oxidation in real wine medium, and finally the development of innovative strategy for quality improvement and shelf-life extension of white wines. Comparison of different methods for O2 and CO2 measurement in wine The initial part of the present work was to determine a reliable quantification method for dissolved oxygen quantification in wine medium. Since dissolved carbon dioxide present in wine may influence the oxygen concentration, its amount should also be taken into account. Thus, development of dissolved carbon dioxide determination was of major importance for the further experiments described in this thesis. The main aim of the first study was to give a review of the oxygen and carbon dioxide measurement principles and to compare several instruments for carbon dioxide and oxygen measurement in wine available in the market. For carbon dioxide determination, CarboQC, Orbisphere 3658 and agitation cylinder were used. Oxygen measurements were conducted with PreSens, OxyQC and Orbisphere 3650. Sample bottles were prepared with concentrations in the range from 0 to 2200 mg/L for carbon dioxide and from 0 to 12 mg/L for oxygen, respectively, dissolved in white wine of Müller Thurgau variety. O2 and CO2 measurements with six instruments were sequentially conducted at 20°C after 10 minutes shaking of trial bottles. Subsequently calculated concentrations of oxygen and carbon dioxide were used for correlation regression tests. From the data obtained for CO2, three investigated instruments showed good repeatable measurement results (R2=98%) in the range from 0 to 1500 mg/L. However, in the wine samples oversaturated with CO2 (>1500 mg/L at 20°C) CarboQC and Orbisphere 3658 showed significantly higher precision (R2=99%), compared to the agitation cylinder, due to carbon dioxide losses during filling of the cylinder. As for oxygen data, results obtained with each of the measurement devices (PreSens, OxyQC and Orbisphere 3650) demonstrated good correlation with the initial oxygen amount in wine samples (R2=98%) in the whole monitored range of dissolved oxygen concentrations. However, due to the flexibility of PreSens mini-sensor application inside the bottle and noninvasive measurement, this technique was found to be more advantageous, compared to the other two. Additionally, it allowed not only determination of dissolved oxygen, but also of the gaseous oxygen concentration in a bottle headspace. For these reasons, the PreSens device was chosen for further experiments. Effect of Headspace Volume and Iron and Copper Addition on Oxidation Processes in Model Solution and Riesling Wine: Chemical and Sensory Changes Since previous studies in model solutions published by other authors clearly showed the key role of iron and copper in oxidation reactions in wine, the main aim of this part of the thesis was to compare the effects of oxygen and iron and copper additions on oxygen consumption rate, sulphur dioxide and colour of bottled model solution and actual wine with similar properties. Model solution was prepared of deionised water, glycerol, (+)-tartaric acid, ethanol, gallic acid and potassium metabisulfite to reach a free sulphur dioxide concentration of 50 mg/L. 200 L Riesling wine (vintage 2010) was prepared using standard winemaking techniques and equipment, and was subsequently treated with potassium ferrocyanide to eliminate iron and copper. Model solution and Riesling wine were bottled in 500 mL bottles with and without small additions of iron (0.1 mg/L) and copper (0.05 mg/L). Oxygen concentration in bottles was adjusted using various headspace volumes (0, 50 and 100 mL for model solution, and 0, 20 and 40 mL for Riesling, respectively) full of ambient air. Iron and copper concentration, total consumed oxygen, sulphur dioxide, browning rate (E420) were monitored. Additionally, sensory analysis of bottled Riesling wines (triangle tests and descriptive analysis) was conducted after 90 and 240 days of storage. The results revealed major differences between model solution and real wine. In model solution the headspace volume and the metal addition contributed to significant changes in total consumed oxygen, colour, and free sulphur dioxide. The metal addition increased the rate of the molecular oxygen consumption and resulted in elevated consumption of free SO2. Enhanced colour was observed in all wines, where iron was added. The experiment with Riesling wine with similar parameters showed strong influence of the headspace volume. The rate of oxidative browning and oxygen consumption rate strongly correlated with the headspace volume at the bottling. In contrast to model solution experiment, addition of small concentrations of iron and copper did not contribute to the colour and oxygen consumption rate of Riesling wine. Sensory analysis showed that the wines bottled with 0, 20 mL and 40 mL HS volume became significantly different already after three months of storage at 15°C, which was proved by the triangle tests. Descriptive analysis after six and nine months of storage confirmed negative influence of headspace volume, thus proving the significance of oxygen ingress at bottling on wine quality. Moreover, traces of metals in Riesling wines even in the wines with no iron and copper addition were sufficient to initialise oxidation processes. However, since small iron and copper additions had significant impact on model solution, further studies with Riesling wine needed to be conducted. The Impact of Headspace Oxygen and Copper and Iron Addition on Oxygen Consumption Rate, Sulphur Dioxide Loss, Colour and Sensory Properties of Riesling Wine For further investigation of the impact of iron and copper on white wine oxidation, Riesling wine was bottled with the addition of 1 mg/L of iron and 0.5 mg/L of copper, which correspond to average iron and copper concentrations in wines of Baden-Württemberg. Oxygen concentrations were determined, as previously reported, by the headspace volume in the bottle (0 mL, 10 mL and 20 mL) full with ambient air. In contrast to the previous experiment, addition of 1 mg/L of iron and 0.5 mg/L of copper had significant influence on the oxygen consumption rate, on the loss of free SO2 during storage, and on the sensory changes in wine. Addition of iron and copper significantly catalysed the oxygen consumption. Free sulphur dioxide loss was found to be proportional to the total consumed oxygen after bottling. Moreover, in all wines with iron and copper addition free sulphur dioxide decay was significantly elevated compared to wines with no iron and copper addition. Although colour changes were not observed in wines after 90 days of storage, significant sensory changes were detected. Both oxygen and iron and copper addition made an impact on sensory evaluation of wines. At low oxygen concentration (0 mL headspace) metal addition had positive effect resulting in elimination reduced aromas. In contrast, for 10 mL and 20 mL headspace, wines with iron and copper addition showed lower scores in fruity, citrus, tropical aromas, and elevated scores in untypical aging and had pronounced oxidised character. The results of the study indicate that, in the case of Riesling wine, excessive oxygen exposure due to oxygen present in the headspace of the bottle should be avoided. Moreover, iron and copper concentration also seems to make significant impact on oxygen and SO2 consumption rates and on sensory perception of wines. These findings suggest that iron and copper concentrations should also be taken into account, when oxygen management strategy is defined. Effect of Headspace Volume, Ascorbic Acid and Sulphur Dioxide on Composition and Sensory Profile of Riesling Wine In the last part of the present work the effects of different oxygen and free SO2 levels, and ascorbic acid addition on the development of white wine were investigated. Riesling wine was bottled in 500 mL bottles with four different headspace volumes (0 mL, 10 mL, 20 mL, 30 mL), two levels of free SO2 (50 mg/L and 70 mg/L), and with and without ascorbic acid (250 mg/L) addition. Dissolved oxygen and the oxygen in headspace were measured in the resulting 17 wines. Free and total SO2 concentrations, ascorbic acid concentration, colour, redox potential, and antioxidative capacity were measured regularly in wine samples. After six months of storage, the wines were evaluated using sensory descriptive analysis. It was again proved that wine exposure to oxygen at bottling plays a key role in white wine development during storage. High oxygen ingress may greatly influence the redox state of wine and affect the important quality parameters including colour, free and total SO2, and the overall sensory quality of wine. Free and total sulphur dioxide loss and the decline in ascorbic acid could be linked to the total consumed oxygen content. It was observed that in the presence of ascorbic acid less sulphite was consumed. Ascorbic acid addition also contributed to the fruity and fresh character of the bottled wines, which indicates its strong antioxidant. However, when combined with high oxygen concentration, ascorbic acid addition promoted enhanced white wine browning. This was scavenged in the wines with higher free SO2 concentrations. Based on the data shown, careful control of the oxygen ingress during bottling is crucial for white wine quality. Ascorbic acid addition seems to have positive sensory effects on the development of wines during the post-bottling period. However, the possible wine browning, associated with ascorbic acid, should be taken into account. On the contrary, sulphur dioxide, in case of the Riesling wine studied, seems to be less effective to prevent negative sensory effects in wines due to excessive exposure to oxygen, but may simultaneously decrease oxidative browning in wines with ascorbic acid addition. In summary, low oxygen ingress at bottling combined with low iron and copper concentrations, moderate additions of ascorbic acid and sulphur dioxide seem to be a good oxygen management strategy and offer a good potential to improve quality and extent the shelf-life of white wines.Der Weltweinmarkt und speziell der europäische Weinmarkt wird heute oft als übersättigt angesehen. Der Erfolg einzelner Weinproduzenten hängt daher vom Verständnis und der Adaption an die Bedürfnisse der Verbraucher ab. Bei Weiß- und Roséweinen schätzen Verbraucher derzeit besonders einen fruchtigen, frischen Charakter. Oxidative Noten sind unerwünscht. Dennoch gehören sie zu den häufigsten Weinfehlern. Aus Weinwettbewerben wurde berichtet, dass bis zu 48% der fehlerhaften Weine von den Prüfern wegen Oxidationsnoten beanstandet wurden. Sauerstoff kann vom Wein während des ganzen Weinbereitungsprozesses aufgenommen werden. Die Sauerstoffaufnahme hängt im Wesentlichen von den Prozessen und der verwendeten technologischen Ausstattung ab. Unter normalen Bedingungen kann Sauerstoff bis zu 8.8 mg/L im Wein gelöst werden. Gelöster Sauerstoff in Wein wird in der Regel durch chemische Reaktionen von molekularem Sauerstoff mit Weininhaltsstoffen bis unter die Nachweisgrenze verringert. Die vielfältigen Reaktionen der Weinoxidation sind sehr komplexe Prozesse. Ihre Auswirkungen variieren erheblich. Beeinflussende Faktoren sind Weintyp, Weinbehandlung, Sauerstoffmenge, chemische Zusammensetzung des Weines, pH-Wert, Lagertemperatur, Belichtung, Metallgehalt und Redox-Zustand des Weines. Die Wirkung von Sauerstoff ist äußerst komplex, die Weinfarbe und das Aroma kann verbessert oder gar ruiniert werden. Weißweine werden durch Sauerstoff häufig negativ verändert. Der Sauerstoff führt hier zu schnellem Aromaverlust bis hin zu oxidativer Bräunung. Gerade dies wird vom Verbraucher oft negativ bewertet. Bei Rotweinen hingegen kann Sauerstoff gezielt eingesetzt werden um die Farbe zu stabilisieren oder reduktive Aromen zu entfernen. Die Forschung über Weinoxidation konzentriert sich derzeit auf Experimente in Modell-Lösungen. Diese Studien geben wertvolle Informationen über Mechanismen und Hintergründe der Oxidation. Jedoch befassen sich derzeit nur wenige Experimente mit echtem Wein. Bei echten Weinen bietet sich die Möglichkeit analytische und sensorische Daten miteinander zu verknüpfen. Wichtiger Punkt der vorliegenden Arbeit ist die umfassende Bewertung verschiedener Einflußfaktoren auf die Weinalterung. Aus den Ergebnissen wurde eine Strategie für die Verbesserung der Qualität und einer Verlängerung der Haltbarkeit von Weißweinen entwickelt. Methodenvergleich zur O2 -und CO2- Bestimmung im Wein Der erste Teil der vorliegenden Arbeit besteht in der Bestimmung von zuverlässigen Methoden zur Quantifizierung des gelösten Sauerstoffs im Wein. Da das gelöste Kohlendioxid im Wein die Sauerstoffkonzentration beeinflussen kann, wurde die CO2-Menge ebenfalls berücksichtigt. Folglich war die Entwicklung einer Methode zur Kohlendioxid-Bestimmung auch von großer Bedeutung für die weiteren Versuche, die in dieser Arbeit beschrieben sind. Das Hauptziel der ersten Studie war es, einen Überblick zu aktuellen Sauerstoff- und Kohlendioxid-Messmethoden zu geben sowie verschiedene auf dem Markt verfügbare Instrumente für Kohlendioxid- und Sauerstoff-Messung in Wein zu vergleichen. Sauerstoff-Messungen wurden mit PreSens, OxyQC und Orbisphere 3650 durchgeführt. Zur Kohlendioxid-Bestimmung wurden CarboQC, Orbisphere 3658 und Schüttelzylinder verwendet. Probenflaschen wurden mit Konzentrationen im Bereich von 0 bis 2200 mg/L für Kohlendioxid und von 0 bis 12 mg/L für Sauerstoff abgefüllt. O2- und CO2- Messungen erfolgten mit den sechs Instrumenten nacheinander bei 20°C, nachdem die Flaschen für 10 Minuten geschüttelt wurden. Die anschließend berechneten Konzentrationen an Sauerstoff und Kohlendioxid wurden für die Erstellung von Korrelationen und Regression-Tests verwendet. Die drei untersuchten Instrumente für CO2-Bestimmung zeigten reproduzierbare Messergebnisse (R2 = 98%) im Bereich von 0 bis 1500 mg/L. Doch in den Weinproben bei dem 20°C übersättigten Bereich (>1500 mg/L) zeigten CarboQC und Orbisphere 3658 signifikant höhere Präzision (R2 = 99%) im Vergleich zum Schüttelzylinder. Dies ist logisch, da während der Befüllung des Zylinders das Kohlendioxid verloren geht. Die Ergebnisse der Sauerstoff-Messungen deuteten darauf hin, dass PreSens, sowie auch OxyQC und Orbisphere 3650 eine im gesamten überwachten Bereich der Sauerstoffkonzentrationen verlässliche und kongruente Werte liefern. Aufgrund der Flexibilität der Minisensoren, die direkt in die Flasche eingeklebt werden können, erwies sich die nicht-invasive O2-Messung mittels PreSens als vorteilhaft. Darüber hinaus erlaubt diese Technik nicht nur die Bestimmung vom gelöstem Sauerstoff, sondern auch die Messung vom gasförmigen Sauerstoff im Kopfraum. Aus diesen Gründen wurde das PreSens-Gerät für weitere Experimente ausgewählt. Einfluss vom Kopfraumvolumen und Eisen- und Kupfer-Zugabe auf Oxidation in Modell-Lösung und Riesling Wein: chemische und sensorische Veränderungen In früheren veröffentlichten Studien in Modell-Lösungen wurde die wichtige Rolle von Eisen und Kupfer in Oxidationsreaktionen in Wein deutlich gezeigt. Im zweiten Teil der vorliegenden Arbeit wurden die Wirkungen von unterschiedlichen Sauerstoff-Mengen bei der Abfüllung untersucht. Des Weiteren wurde der Einfluss von Eisen- und Kupfer-Zusätzen auf die Sauerstoffverbrauchsrate, Schwefeldioxid und Farbe in Modell-Lösung und Riesling Wein geprüft. Die Modell-Lösung wurde aus hochreinem Wasser, Glycerin, (+)-Weinsäure, Ethanol, Gallussäure und Kaliummetabisulfit zusammengestellt, außerdem wurde die SO2-Konzentration auf 50 mg/L eingestellt. 200 L Riesling (Jahrgang 2010) wurde unter Verwendung von Standard-Techniken der Weinbereitung produziert und anschließend mit Kaliumhexacyanoferrat behandelt, um die Metalle bzw. Eisen und Kupfer zu entfernen. Modell-Lösung und Riesling wurden in 500-mL Flaschen mit und ohne Zusatz von Eisen (0.1 mg/L) und Kupfer (0.05 mg/L) abgefüllt. Die Sauerstoffkonzentration in Flaschen wurde mit Luft im Kopfraum (0, 50 und 100 mL für Modell-Lösung und 0, 20 und 40 mL für Riesling) eingestellt. Die Eisen- und Kupferkonzentrationen, Gesamtmenge an verbrauchtem Sauerstoff, Schwefeldioxid, Absorption (E420) wurden während der Lagerzeit beobachtet. Zusätzlich wurde die sensorische Bewertung von Riesling Weinen mittels Dreieckstests und deskriptiver Analyse nach 90 und 240 Tagen Lagerung durchgeführt. Die Ergebnisse zeigten große Unterschiede zwischen der Modell-Lösung und dem Riesling Wein. In der Modell-Lösung hatte das Kopfraumvolumen und der Metall-Zusatz dazu beigetragen, dass wesentliche Änderungen in Sauerstoffverbrauchsrate, Farbe und freiem Schwefeldioxid entstanden. Der Eisen- und Kupfer-Zusatz erhöhte die Geschwindigkeit des Sauerstoff-Verbrauchs und führte zu erhöhtem Verbrauch der freien SO2. Die intensive Farbentwicklung wurde in allen Weinen mit Eisen-Zusatz festgestellt. Das Experiment mit Riesling mit vergleichbaren Parametern zeigte einen starken Einfluss des Kopfraumvolumens. Die Sauerstoffverbrauchsrate und die oxidative Bräunung korrelierten stark mit dem Kopfraumvolumen. Im Gegensatz zum Modell-Lösung-Experiment hatte die Zugabe von geringen Mengen an Eisen und Kupfer keinen Einfluss auf die Farbe und den Sauerstoffverbrauch im Riesling Wein. Sensorische Unterschiede zwischen den Weinen mit 0, 20 und 40 mL Kopfraum wurden bereits nach drei Monaten Lagerung bei 15°C durch die Dreieckstests nachgewiesen. Die deskriptive sensorische Analyse nach sechs und neun Monaten Lagerung bestätigte den negativen Einfluss von großem Kopfraumvolumen. Dies beweist die große Bedeutung der Sauerstoffaufnahme bei der Abfüllung auf die Weinqualität. Außerdem waren Metallmengen im Riesling Wein, auch in den Varianten ohne Eisen- und Kupferzusatz ausreichend, die Oxidationsprozesse zu initialisieren. Da die geringen Eisen- und Kupferzugaben eine erhebliche Wirkung in der Modell-Lösung und nicht im Wein hatten, waren weitere Studien mit größeren Mengen an Eisen und Kupfer in Riesling Wein erforderlich. Einfluss von Sauerstoff im Kopfraum, Eisen- und Kupferzusatz auf Sauerstoffverbrauchsrate, Schwefeldioxidverlust, Farbe und sensorische Eigenschaften von Riesling Wein Um die Wirkung von Eisen und Kupfer weiter auf Weißweinoxidation zu untersuchen, wurde Riesling Wein mit/ohne Zugabe von 1 mg/L Eisen und 0.5 mg/L Kupfer abgefüllt. Dies entspricht den durchschnittlichen Eisen- und Kupfer-Konzentrationen in Weinen aus Baden-Württemberg. Die Sauerstoffmengen wurden mit verschiedenen Kopfraumvolumen in den Flaschen (0, 10 und 20 mL) bestimmt. Im Gegensatz zum vorangegangenen Versuch, hatte die Zugabe von 1 mg/L Eisen und 0.5 mg/L Kupfer einen signifikanten Einfluss auf den Sauerstoffverbrauch, Verlust von freiem SO2 während der Lagerung und auf die sensorischen Eigenschaften im Wein. Der Eisen- und Kupfer-Zusatz katalysierte deutlich den Sauerstoffverbrauch. Der Schwefeldioxid-Verlust war proportional zur Gesamtmenge an verbrauchtem Sauerstoff. Zusätzlich wurde der SO2-Abbau in allen Varianten mit Eisen und Kupfer im Vergleich zu den Varianten ohne Eisen- und Kupferzugabe signifikant erhöht. Obwohl die Farbänderungen nach 90 Tagen Lagerung nicht festgestellt werden konnten, waren die erheblichen sensorischen Veränderungen bereits erkennbar. Der Sauerstoff, wie auch der Eisen- und Kupferzusatz hatten Einfluss auf die sensorische Bewertung der Weine. Bei niedrigen Sauerstoffkonzentration (0 mL Kopfraum) hatten Metalle durch die Eliminierung von reduzierten Aromen eine positive Wirkung. Die Weine mit 10 und 20 mL Kopfraum und zugesetztem Eisen und Kupfer zeigten geringere Ausprägungen in Attributen wie Frucht, Citrus, tropischen Aromen und erhöhte Werte in UTA und hatten einen deutlichen oxidierten Charakter. D