In order to avoid wine spoilage, most wineries add sulphur dioxide to the wine. However, sulphites dissolved in the wine can potentially cause allergies. An alternative preservation method without or with significantly reduced sulphite addition has been developed by an international consortium within the EU-funded project "PreserveWine-DEMO", in which the Fraunhofer IGB is involved.
A good glass of wine is a byword for quality of life – not just for connoisseurs. In order to avoid wine spoilage, wineries mostly add sulphur dioxide during the winemaking process. However, the sulphites that dissolve in wine can cause allergic reactions – including asthma. Within the EU they must therefore be declared as an ingredient on the label and the limits for sulphites in wine have been reduced.
Sulphites unfold their preservative action in two ways. On the one hand they inactivate microorganisms, such as unwanted yeasts, acetic acid bacteria and lactic acid bacteria, thus protecting wine from spoilage. Secondly, they act as antioxidants and protect delicate flavours against oxidation. Both effects ensure that wine is preserved and can be stored for ageing.
Conventional alternative physical preservation methods such as filtration are suited for wine only to a limited extent, because they also remove colour and valuable flavours. Other methods operating at high temperatures, such as pasteurization, are unsuited as they destroy heat-sensitive ingredients.
A new method for preservation of liquid foods, working at moderate temperatures and therefore referred to as "cold pasteurization", is the so-called pressure change technology, which has been developed and patented by the Dresden company Edecto for fruit juice within the framework of a nationally funded project .
"The physical process has effects similar to those of sulphurization of the wine: growth of microorganisms is prevented because the cells are mechanically disrupted. In addition, the protective atmosphere of an inert gas decreases oxidation reactions, so drinks are stabilized," explains Edith Klingner, a physicist at Edecto, who coordinates the EU-funded project "PreserveWine-DEMO".
In the initial PreserveWine project, international partners including Edecto investigated whether the new method can also be applied to wine. At the Fraunhofer IGB a batch plant was modified and on the basis of initial results a continuous plant was developed and built. The TÜV-approved pilot plant can treat up to 120 litres of wine per hour at a pressure of 250 to 500 bar and at temperatures below 40°C.
The results are promising for the treatment of white wine as well as red wine. “Unwanted oxidizing enzymes are inactivated, while neither temperature-sensitive ingredients nor colour and taste are altered by the treatment," confirms Dr. Ana Lucía Vásquez-Caicedo, food technologist and group manager at the Fraunhofer IGB.
In the pressure change technology a chemically inert gas, such as nitrogen or argon, is dissolved at high pressure in the liquid to be preserved. When the liquid is exposed to a high pressure of up to 500 bar, the solubility of the gas increases in the liquid. As a result, the dissolved gas also diffuses into the microbial cells. When the pressure is finally abruptly decreased, the gas expands – even within the cells – and causes these to burst. The previously dissolved gas then goes back into the gas phase and is recovered for reuse.
"In studies at the Fraunhofer IGB and our partner institute ADERA we have shown that the colour of the wine is maintained over time during storage in barrels or bottles. In wine tastings, we found that the taste is not affected," says Vásquez-Caicedo. The new preservation method can be used in different stages of wine production: after vinification (wine pressing) of white wine, after the alcoholic fermentation, after the malolactic fermentation employed mainly in red wine for acid degradation as well as when racking and filling.
In the follow-up project "PreserveWine-DEMO" the process will be transferred as a winery process to industrial scale. To this end, the researchers want to build a mobile plant that can be tested on site in various wineries. In parallel, the consortium aims to ensure product quality and process feasibility and wants to examine consumer acceptance of the new technology.
The previous results have been achieved in the project "PreserveWine" (Grant Agreement No. 262507), which was funded from December 2010 to November 2012 in the European Union’s 7th Research Framework Programme. The follow-up project "PreserveWine-DEMO – Demonstration of a non-thermal process to replace use of sulphites and other chemical preservatives in European wines to meet new European Directive" (Grant Agreement No. 606569) has been funded in the EU’s 7th Research Framework Programme since January 2014. Project partners are the Fraunhofer IGB (Germany) and the Association pour le Développement de l'Enseignement et des Recherches auprès des Universités des Centres de Recherche et des Entreprises d'Aquitaine (France) as research partners, the companies Edecto (Germany), Statiflo (UK), Uvasol (UK) and Malthe Winje (Norway) as technology suppliers, the Société Civile Agricole du Château Guiraud (France) as a user as well as the winery association Comité de la Communauté économique Européenne Industries Commerce Vins (Belgium).
Dr. Claudia Vorbeck | Fraunhofer-Institut
How to become a T follicular helper cell
31.07.2015 | La Jolla Institute for Allergy and Immunology
Heating and cooling with light leads to ultrafast DNA diagnostics
31.07.2015 | University of California - Berkeley
Using ultracold atoms trapped in light crystals, scientists from the MPQ, LMU, and the Weizmann Institute observe a novel state of matter that never thermalizes.
What happens if one mixes cold and hot water? After some initial dynamics, one is left with lukewarm water—the system has thermalized to a new thermal...
Physicists from Regensburg and Marburg, Germany have succeeded in taking a slow-motion movie of speeding electrons in a solid driven by a strong light wave. In the process, they have unraveled a novel quantum phenomenon, which will be reported in the forthcoming edition of Nature.
The advent of ever faster electronics featuring clock rates up to the multiple-gigahertz range has revolutionized our day-to-day life. Researchers and...
Researchers have developed an ultrafast light-emitting device that can flip on and off 90 billion times a second and could form the basis of optical computing.
Joint BioEnergy Institute study identifies bacterial protein that is key to protecting rice against bacterial blight
A bacterial signal that when recognized by rice plants enables the plants to resist a devastating blight disease has been identified by a multi-national team...
Researchers in the Cockrell School of Engineering at The University of Texas at Austin are one step closer to delivering smart windows with a new level of energy efficiency, engineering materials that allow windows to reveal light without transferring heat and, conversely, to block light while allowing heat transmission, as described in two new research papers.
By allowing indoor occupants to more precisely control the energy and sunlight passing through a window, the new materials could significantly reduce costs for...
23.07.2015 | Event News
10.07.2015 | Event News
25.06.2015 | Event News
31.07.2015 | Trade Fair News
31.07.2015 | Transportation and Logistics
31.07.2015 | Physics and Astronomy