Method and compositions for preserving wine

This application claims priority from provisional application Ser. No. 61/019,745, filed Jan. 8, 2008, the entire contents of which are hereby incorporated by reference.

The present application relates to a method and compositions for preserving wine.

Wine is traditionally defined as an alcoholic beverage produced when fruit undergoes primary fermentation in which yeast converts the sugar in fruit to alcohol. When the sugar supply is exhausted, the yeast dies off, leaving the alcohol produced to blend with, or attach to, other components.

Almost all wine improves with aging. However, peak flavor and bouquet may require years to develop in wines with high concentrations of tannins, and many wines deteriorate not long after reaching their peak. Chemical reactions during the aging process are extremely complex and well documented. The desirable characteristics of wine result from a long term blending of the components in the wine.

The traditional wine aging process is simple, well known, and well understood. Oxidation is among the greatest problems with which a winemaker deals during the making and aging process for wine. Oxidation can adversely affect the fruity flavor and freshness of wine. In order to prevent oxidation of the wine, sulfur dioxide (as potassium metabisulfite or sodium metabisulfite) is frequently added to grape must before fermentation to inhibit or kill all unwanted bacteria prior to the point at which the alcohol production commences after fermentation begins. The metabisulfite salts are converted to sulfur dioxide, which is the so-called “free sulfite” of wine. After fermentation produces some alcohol, the sterilizing effects of alcohol assist in killing the unwanted bacteria.

In some wines, particularly those of the Sauternes type, a considerable quantity of naturally-occurring sulfur dioxide is retained in the wine until the wine is bottled. In red wines and in some white wines, sulfur dioxide is added to prevent the wine from becoming unsound.

When sulfur dioxide is first added in the Free State, it rapidly combines with other substances in the wine, so that sometimes in a few minutes, and, in other cases, in as much as thirty minutes, the amount of free sulfur dioxide is halved. Over a period of weeks or months, the exact rate of disappearance depends upon many factors, such as temperature and amount of aeration, whereby the total sulfur dioxide content of the wine falls.

During the normal aging process for wine, the conditioners and preservatives, such as sulfur dioxide, are dispersed throughout the liquid. Changes in the wine following bottling are subtle and difficult to establish, since there are no measurements other than taste and smell that are used to determine when the aging process is complete and when the wine invariably begins its decline. Further, the ingredients used vary among wines and winemakers, and each ingredient may affect the aging process differently.

There is a direct relation between the amount of sulfite added and the inhibition of bacterial growth in wine. As such, large scale wine producers, whose risks are high, may use a higher concentration of additives such as sulfite to avoid spoilage. However, with the addition of large amounts of sulfites, the wine can be adversely affected, irrespective of the lack of bacterial deterioration.

Some smaller wine producers advertise that they do not use sulfite. This is important to many consumers, as some consumers complain of headaches which are attributed to the presence of sulfite in wines, even though all wines contain a small amount of naturally occurring sulfites. Although the relationship between sulfites in wine and headaches has not been clinically confirmed, many believe that the link is real. As such, wines not containing added sulfites may command a higher retail price, because manufacturing costs are higher and the risk of losing entire batches of wine to bacterial contamination and/or oxidation is borne by the consumer.

Although all wines naturally contain some sulfites as a result of the fermentation process, the amounts of these sulfites are not noticeable to most people. However, when sulfites are added to the must, during fermentation and more so after bottling, gaseous hydrogen sulfide develops in the wine. This gas is extremely toxic and, in many cases, may destroy what would otherwise be a good wine. The concept of decanting the wine, or letting the wine “breathe”, in essence allows the hydrogen sulfide to volatilize out of the wine so that it is then suitable for drinking. There is no nutritional value to the sulfites added to wine, and, in the case of sodium metabisulfite, consumers may wish to avoid additional sodium as well.

It has now been discovered that resveratrol; pterostilbene, a natural methoxylated analogue of resveratrol; or a combination of the two compounds, can be used as an antioxidant, fungicide and bactericide in wine. Resveratrol and pterostilbene have no known side effects in humans, and can be used as a replacement for sulfites that are conventionally added to wines as preservatives.

The resveratrol, pterostilbene, or combination thereof, can be added to the grape must prior to fermentation, during fermentation, and at the time of bottling the wine. Since the yeast during fermentation and the alcohol produced during fermentation do not adversely affect the pterostilbene or resveratrol, the time of addition of these compounds is not critical.

Grapes, and some other fruits and vegetables such as Vaccinium berries, normally produce resveratrol as a defense mechanism when being attacked by some extraneous fungi, bacteria or insects. However, the amount of resveratrol the fruit or vegetable produces is only sufficient to protect the individual fruit or vegetable, but it is not nearly enough to protect an entire batch of wine produced from grapes (about 5 mg/kg in red wine). Moreover, different grape varieties produce different amounts of resveratrol.

Resveratrol and/or pterostilbene, whether naturally occurring or synthetic, can be added to wine to act as a preservative. These compounds can be added to wine in amounts ranging from about 10 mg/L to about 10,000 mg/L Ideally, the compounds should be added twice. It is preferable to add pterostilbene during the first step of fermentation because it is less water soluble than resveratrol and thus will create a thin film layer on top of the must, further preventing contact with oxygen and preventing decomposition of the pterostilbene. Resveratrol, which is more stable than pterostilbene, is then added to finished wine to act as an antioxidant during aging and storage of the wine.

Resveratrol and pterostilbene have antibacterial and antifungal activity in wine. (Biochem. Pharmacol. Jan. 15, 2002; 63(2) 99-104).