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Chemistry

Almost like a red

Technique developed by Embrapa increases fourfold the levels of antioxidant compounds in white wine

Miguel Boyayan Polyphenols, such as resveratrol, are found in grape skins and seedsMiguel Boyayan

Since the early 1990’s, when the world was introduced to the so-called French paradox, characterized by the low incidence of heart problems in a population fond of a fatty diet, the moderate consumption of red wine was named as the main element responsible for this unusual situation, which was not in line with the world standard. The explanation for the possible health benefits of this drink , an issue that has caused much controversy in the medical community, was associated with  high levels of antioxidant compounds in the polyphenol category, especially a molecule called resveratrol, found in red wine. As white wine has, on average, ten times less resveratrol than red wine, white wine has become the ugly duckling in the wine world and its consumption has dropped worldwide. But this inferiority complex has been partly softened, thanks to the good results achieved by Embrapa’s Uva e Vinho (Grape and Wine) project in the city of Bento Gonçalves, State of Rio Grande do Sul. After four years of research and tests, Brazilian researchers have developed a technique so that white wine has four times the normal level of polyphenols, especially the highly heralded resveratrol, quercetin and flavonoids.

The new method, which will probably be the target of some kind of legal protection, has already been passed on to a winery in the State. Early last month, Cooperativa Garibaldi, which had entered into a 3-year partnership with Embrapa, launched 20 thousand bottles of Lorena Ativa Acquasantiera, vintage 2008, a dry white wine with a higher resveratrol content. “To produce this wine, we used a combination of three technologies developed by our unit”, says wine maker Mauro Zanus, from Embrapa Uva e Vinho, and the coordinator of the project. The grapes from which the wine was made (BRS Lorena), the yeast used for the fermentation and the wine making protocol (the technical recipe to transform grape juice into wine) are the creation of the research center at Bento Gonçalves. A few days after introducing the Brazilian white wine containing a higher level of anti-oxidants, researchers from the Technology Institute of Israel in Haifa, announced a similar method to raise the amount of polyphenols in this kind of beverage.

Theoretically, it should not be difficult to make a white wine with more resveratrol. This compound is produced whenever the vineyard is attacked by fungi and bacteria or is exposed to aggressive agents, such as ultra violet radiation. Like the grapes used in red wines, the white grapes produce a high quantity of these polyphenols, which are basically found in  grape skins and to a lesser extent, in the seeds and the stems. The problem is that the traditional manner of producing white wine does not favor the extraction of high levels of antioxidant substances. Red wine contains many polyphenols – which are the source of the wine’s color and other characteristics – because it remains for days, sometimes for as long as three weeks, in contact with the skins of the red grapes during maceration, a crucial stage in the preparation of wine. Macerating means the extraction of several active nutritious principles or elements from a solid body by immersing it in liquid. In the case of wine, maceration means leaving the skins and the seeds (the solid parts) in contact with the recently crushed grape juice that is about to initiate the fermentation process. As fermentation occurs, the resulting alcohol acts as a solvent, increasing the solubility of the substances found in the grapes’ skins and seeds. In the case of white wine, maceration is virtually non-existent – it rarely takes longer than three hours.

disseminationThis said, the formula to prepare white wine with more polyphenols seems more than obvious, right? Right. But there is a drawback in practical terms. How can this be done without eliminating the beverage’s characteristics? “We cannot alter the color and the taste of the wine too much”, says Zanus. The most common product resulting from prolonged maceration is a yellowish liquid with a strong bitter taste. In fact, this was the first result obtained by the Embrapa team when, some years ago, the team prepared a white wine with a higher polyphenol content by using Chardonnay grapes.

The initial lack of success did not discourage the Embrapa’s researchers. They put the Chardonnay grapes on one side and put their chips on the BRS Lorena grapes, a complex hybrid, which resulted from the cross breeding of the Malvasia Bianca (from which the BRS Lorena derives 77% of its genetic load) and the Seyval; BRS Lorena was launched in 2001. Robust and able to achieve good maturity and high sugar levels in the Serra Gaúcha hills, the Lorena grapes, whose strong aroma and flavor are reminiscent of Muscatel grapes, proved to be more appropriate for the experiment. Especially because the process included the use of 1 vvt, a special yeast developed by Embrapa, which produces more alcohol during fermentation and accelerates the extraction of various compounds, including resveratrol. All of these factors drove the research forward, but the project’s biggest distinguishing feature was the establishment of the aforementioned wine making protocol. The most critical data of this formula includes the exact maceration time and the fermentation conditions during this period, secrets which are not revealed. The tests conducted at Embrapa showed that white wine achieves its highest production level in terms of antioxidant compound after 12 days of maceration. “But we never leave the wine in contact with the skins for too long , because  it would become yellowish and bitter”, says Zanus.

For the next three years, thanks to the partnership with Embrapa, the Cooperativa Garibaldi alone, a cooperative comprised of 300 families of small producers from the Serra Gaúcha hills, will be able to use the new technique. The company is happy enough with the interest aroused by Lorena Ativa 2008, a somewhat modest product in terms of price: some R$ 10. “The wine is very aromatic, with floral undertones and a golden color; and it is full-bodied”, says wine maker Maiquel Vignatti, who is responsible for the cooperative’s marketing strategies. Although Lorena Ativa contains a maximum 40% of the total polyphenol content of a red wine, it should attract consumers interested in the possible health benefits from drinking it in moderation. In Embrapa’s opinion, the next step is to develop white wine with more resveratrol, prepared from other grape varieties.

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