Skip to main content

Article Category

News

Article available in the folowing languages:

European researchers seek alternatives to sulphur dioxide in wine

Biotechnology researchers in Portugal, Spain and Switzerland have joined forces in a project that aims to reduce or eliminate the amount of sulphur dioxide (SO2) used in making wines. SO2, an effective antimicrobial, antioxidant and preservative agent, is a potential allergen ...

Biotechnology researchers in Portugal, Spain and Switzerland have joined forces in a project that aims to reduce or eliminate the amount of sulphur dioxide (SO2) used in making wines. SO2, an effective antimicrobial, antioxidant and preservative agent, is a potential allergen and can exacerbate asthmatic symptoms. The current project, called 'WineSulfree', is supported by the Eureka intergovernmental initiative. As evidenced by the squinting and loitering seen in most wine sections of supermarkets, wines vary widely from year to year depending on weather and soil conditions. Extreme conditions can lead to higher microbial infection, higher sugar levels, low acidity or nutrient deficiencies, and this in turn leads to an increased need for using antimicrobials and preservatives. Vintage, grape variety and the sanitary conditions of grapes after harvest also have an impact. Sulphur dioxide (SO2) prevents microbiological damage to the taste and colour of wines, both red and white. When added after fermentation it prevents spoilage and prevents fermentation in the bottle; additionally, it is used in combination with citric acid to keep wineries (and the equipment) clean, as bleach cannot be used. Sanitary conditions in winemaking are necessary to keep the levels of required SO2 low. In the EU, current recommended levels of free SO2 in wines are under 160 parts per million (ppm) for red wines and under 210 ppm for white and rosé wines. Higher levels may be used during the making of red wine prior to fermentation in order to stabilise the colour. SO2 also occurs naturally in wines; 'unsulpherated' wines still contain some SO2. These wines have a limited shelf life and are commercially exasperating. Consumer demands for 'healthy' products and the increasing number wine drinkers who are sensitive to sulphites (sufferers commonly report headaches, hay fever and hives) makes finding commercially viable alternatives to SO2 worthwhile. The research group will focus on the use of chitosane (a sugar derived from chitin) or sesquiterpenoids (antioxidant grape skin compounds) as a substitute, and will also examine techniques such as subjecting the wine to high pressure. According to the project's objectives, the development of non-sulphur treatments that use both physical and chemical processes together with the addition of natural compounds can help preserve wine without affecting its smell, taste or nutritional characteristics. 'Wine treatment through high pressure is a recently proposed technology to reduce the micro-organism quantity, and the addition of chitosane shows antioxidant properties that inhibit the white wine browning'. The project hopes to develop efficient and commercially viable treatments as substitutes of sulphur dioxide, 'allowing the production of wines at the industrial-scale with low quantities of or even no sulphur dioxide'. Meanwhile, the EU-funded ORWINE project, which ends in 2009, has sought to provide a scientific background for the development of EU legislative framework around this issue. The project evaluated innovative technologies such as flash-pasteurization, cross-flow microfiltration, pH reduction by bipolar membranes and yeast spraying to reduce microbial grape diseases. It is also studying the use of the bactericidal enzyme lysozyme, which shows promise, and has found metatartaric acid to be a viable stabiliser. Other projects have looked at the viability of using certain peptides produced by lactic acid bacteria that are present in wine. An ORWINE project meeting earlier this year concluded that studies have run for too short a period to offer any conclusions but for now, 'actual research does not offer any product able to replace sulphur with the same conservation capacities'. It is hoped that the efforts of ORWINE and WineSulfree will provide effective and commercially viable alternatives to the use of SO2 in winemaking that will not affect the taste, smell or food value of the wine. WineSulfree will be coordinated by Dao Sul, a small enterprise in Portugal, and is supported by Eureka. Eureka supports businesses, research centres and universities that carry out innovative pan-European projects; its objectives complement those of the European Union's Framework Programme. The organisation is coordinated through national offices and its secretariat is located in Brussels; the European Commission is represented at its annual meetings.

Countries

Italy, Portugal