Browsing by Subject "Wein"

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Analysis of the effects of abolishment of planting rights in the European Union on the wine sector in Rheinland-Pfalz, Germany
(2016) Bogonos, Mariia; Dabbert, Stephan
The production and marketing of wine in the European Union (EU) are governed by the Common Market Organization (CMO) of the EU Common Agricultural Policy (CAP). Since 1976, a crucial point of the CMO with respect to wine has been the regulation of wine production by the system of the planting rights. Consistent with the goal of increasing the competitiveness of EU wine producers on the world market, the 2008 CAP reform included the liberalization of the planting rights regime by 2018 the latest. As a result of intense discussions on the EU and EU Member states levels, the planting rights system has recently been converted into a scheme of authorizations for vine plantings, which is valid until 2030. This dissertation investigates the effects of abolishment of planting rights on the largest wine-producing region in Germany, Rheinland-Pfalz. For this purpose a comparative static regional partial net-trade equilibrium model that includes the output of a Markov chain projection was used. The model simulates the future distribution of vineyards in Rheinland-Pfalz among wine farm groups according to size classes and area type, the demand for standard and basic quality wine must in Germany and production of standard and basic quality wine must in Rheinland-Pfalz. The policy simulation model was run for scenarios of different levels of market prices of wine must, different land rental prices, restricted and liberalized planting rights, and a scheme of authorizations for vine plantings. The results revealed that the effects of liberalization of planting rights and of a scheme of authorizations for vine plantings depend on profitability of standard and basic quality wine must production. In particular, if standard and basic quality wine must production is profitable for at least one wine farm group, and planting rights are liberalized, production of standard and basic quality wine must and, respectively, acreage of vineyards in Rheinland-Pfalz will increase with respect to the demand for these two types of wine must in Germany and availability of land suitable for vine growing. If production of basic and standard quality wine must is profitable and planting rights regime is retained or converted into a scheme of authorizations for vine plantings, the acreage of vineyards in Rheinland-Pfalz might reach the maximum defined by the policy regime. In addition, newly established vineyards will be used for production of either standard or basic quality wine must depending on which type is more profitable. Movement of vineyards within the wine farm groups will take place only if at least one of the farm groups receives positive economic profits. Land for vine growing will be distributed to the farm groups which are profitable and characterized by positive growth rates in the past. The abolishment of planting rights will have minor or no effects on the wine sector in Rheinland-Pfalz, if production of basic and standard quality wine must is not profitable. Similarly, movement of vineyards within the wine farm groups will not take place, if none of the farm groups receive positive economic profits. This dissertation provided an empirical examination of the effects of restricted and liberalized planting rights, as well as a scheme of authorizations for vine plantings on the wine sector in Rheinland-Pfalz. It has also supplemented the literature on how policy reforms with regard to the limitation of agricultural production input use in order to control the output affect the agricultural production sector.
Detektion von Schadhefen in Wein mittels mit Flusszytometrie analysierter in situ Hybridisierung (Flow-FISH)
(2021) Willberger, Ilka Nadine; Scharfenberger-Schmeer, Maren
In oenological practice, mostly unpasteurised grape musts are used. This leads to an increased introduction of non-saccharomyces, which can have a lasting effect on the fermentation process. Disturbances in the fermentation process are usually only detected in practice on the basis of abnormalities in selected parameters such as sugar content or temperature or the occurrence of off-flavours. The fermenting yeast population may already be so affected at this point that intervention in the fermentation process can no longer prevent the occurrence of off-flavours in the end product or incomplete fermentation. With the help of flow cytometry, an efficient method using FISH (Fluorescence In Situ Hybridisation) was developed to detect and quantify the common representatives of the fermentation population such as Sacchoromyces cerevisiae and the harmful yeast population such as Hanseniaspora uvarum, Dekkera bruxellensis and Pichia anomala in the course of fermentation. Rapid detection enables countermeasures to be taken in good time before a harmful yeast population can have too great of an influence on the course of fermentation and the metabolites formed. Flow-FISH was established with pure cultures from strain collections in defined medium (YPD) and pasteurised white grape must. Samples are extracted and fixated directly from fermentation mixtures. For hybridisation, 18S- and 26S-rRNA probes with FITC-labelling are used. For the evaluation of the flowcytometric data, the Overton-subtraction method is used in this work. This allows a more accurate assessment of the hybridised cell population than the usual setting of a marker. For this purpose, an effective negative control with complementary sequence to the universal eukaryote probe (Euk516) is introduced. Subsequently, the method already known from the literature was optimised with regard to hybridisation conditions and cell fixation and thus adapted to the requirements of a quantitative flow cytometric analysis. With fixation in formaldehyde or in ethanol, fixation methods were developed that fulfil the requirements of both rapid and reliable fixation in the laboratory and rapid fixation in the cellar, if transport to the laboratory is not possible in a timely manner.Helper probes were designed to increase the fluorescence intensity. They are unlabelled and bind in the direct proximity of the specific probe. In all yeast species investigated, S. cerevisiae, H. uvarum, D. bruxellensis and P. anomala, the fluorescence intensity can be considerably increased by using the helper probes. In the case of D. bruxellensis and P. anomala, detection is only possible with the use of the helper probes. The helper probes allow the Flow-FISH assay to be used in a broader growth range of the yeast culture. Without helper probes, quantitative detection is limited to the middle logarithmic growth phase. With helper probes, hybridised cells can be reliably detected starting in the early logarithmic growth phase up until the stationary phase. This covers the critical phase of fermentative activity so that increasing contamination can be detected in the fermentation.The specificity of the probes is given. In part, there are slightly increased fluorescence intensities compared to the negative control, especially with the D. bruxellensis probe combination and non-specific yeasts, which can probably be attributed to increased binding due to the composition of this probe combination.The Flow-FISH assay is also reliable in mixtures of different yeast species and up to a cell count of 10³ cells / ml in the initial fermentation. This detection limit is also achieved by other methods in molecular biology for yeast detection. In contrast to most of these methods, Flow-FISH can also quantify the number of yeasts present. Additionally the use of the flow cytometer offers a simple variant to determine the total cell count of all yeasts in the fermentation. The detection limit of Flow-FISH allows detection before the damage threshold values of the yeasts examined are reached. The Flow-FISH method presented in this dissertation can also be applied to other yeast strains, some of which also originate from wild isolates. A transferability to native fermentations from oenological practice is given. It was possible to examine both spontaneous fermentations and inoculated fermentations in practice fermentations in steel tanks for their yeast population composition and to follow their development in the course of fermentation. Due to the use of flow cytometry and the helper probes and negative control used in this dissertation, the optimised Flow-FISH assay offers a stable basis for the continued development of a test system for use in oenological practice.
Impact of oxygen on quality of white wine
(2013) Morozova, Ksenia; Schwack, Wolfgang
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.
UV-C-Behandlung von Traubenmost zur Inaktivierung von Mikroorganismen
(2018) Diesler, Kathrin; Scharfenberger-Schmeer, Maren
The development of new preservation process techniques to protect ingredients and maintain a high quality standard is always a main goal in the food industry. In course of this, microbial safety has top priority. UV-C technology is a modern, non-thermal process with high efficiency. It has been used for sterilization and treatment of drinking water for many years. Also, ultraviolet radiation for disinfection purposes is already being used in other areas of food production. To what extent this method can be successfully applied in the field of grape must production, will be investigated in this dissertation. For this purpose, several yeasts and bacteria, relevant in this area, were examined for their inactivation potential by UV-C treatment. To ensure the best possible microbial inactivation in must, it is essential to determine an ideal treatment dose for both yeasts and bacteria. The results have confirmed that bacteria are far more sensitive to UV C treatment, than yeasts. It was also shown that there are major differences in UV-C stability within the seven yeast species and six bacteria species used in this study. The analyses have identified Metschnikowia pulcherrima and Acetobacter aceti as the most UV-C stable and Brettanomyces custerianus and Pediococcus sp. as the most sensitive organisms. Furthermore, three morphologically different Brettanomyces strains were used to show that there are also strain-specific variances in the response to UV-C treatment. Using Saccharomyces cerevisiae as an example, a potential formation of UV-C resistance was also ruled out. For this purpose, yeast cells were exposed to a dose, that did not result in complete inactivation. The surviving cells were cultured and retreated. Even after repeating this process eight times, no change in the UV-C response of the yeast cells could be detected. For the application of UV-C technology in the juice and wine industry it has to be ensured, that microorganisms are killed directly and their enzymatic activities are directly inhibited. Yeasts and bacteria could further convert sugar to alcohol or form unwanted metabolic byproducts. Therefore, the enzymatic activity after the initial treatment and during the inactivation process of Saccharomyces cerevisiae was analyzed in more detail. HPLC was used to determine the content of glucose, fructose and ethanol. No enzymatic activity could be detected in the UV-C treated samples from the moment after the initial UV-C treatment, up to the day of complete destruction. However, the effectiveness of UV-C treatment of must and wine cannot be attributed solely to the responsiveness of the various microorganisms. Other product parameters such as grape variety, turbidity and optical density also play a decisive role. In this context, four different musts with different optical density and turbidity were treated and the inactivation kinetics of Saccharomyces cerevisiae were compared. In this work it could be proved, that with an increasing optical density and a higher turbidity, the efficiency of the UV-C treatment in must decreases strongly. The success of a treatment is also directly dependent on the initial contamination rate of the product. Tests with different starting cell numbers have shown, that the required inactivation dose also has to be increased, as the number of cells increases. In the winemaking process, however, not only yeasts and bacteria can be a potential source of danger. The fungal infection of grapes by Botrytis cinerea also carries a high risk. The polyphenol oxidase laccase, produced by the fungus, damages ingredients and leads to a colour change in must and wine. In the investigations it could be proven, that it is possible to strongly reduce or completely inactivate the enzymatic activity in Botrytis infected must, depending on the starting concentration. In summary, UV-C technology represents an effective alternative and extension for current oenological practice. It offers the possibility to inactivate a large number of wine relevant microorganisms without causing resistance. In addition, this work has created a new framework for the application of must specific parameters. The results for the inactivation of the enzyme laccase are also proved to be extremely promising.