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QUESTION - I read a new potentially harmful substance has been discovered inalcoholic beverages. Can you tell me about it?

ANSWER - A compound called urethane, or ethyl carbonate, forms as a by-product during the manufacturing of certain alcoholic drinks. It has been shown to cause cancer in some laboratory animals. The compound forms during fermentation and, if heated during the processing of alcohol, levels can increase. To some extent, therefore, the effect is unavoidable.Levels also may be affected by the soil in which grapes are grown, the variety of grape used and even the weather. Urethane levels can increase in some products, especially wines, during shipping, storage and handling. Some processing can raise urethane levels. Using urea to stimulate fermentation in wine production has been abandoned for that reason.

Concern first surfaced late in 1985 when Canadian authorities found the chemical in certain wines and distilled spirits. At that time the Food and Drug Administration (FDA) and the Bureau of Alcohol, Tobacco and Firearms (ATF), which share responsibility for regulating alcohol, began to seek ways to reduce or eliminate the compound from alcoholic beverages. Because as many as 400,000 different labels of alcoholic beverages may be on the market, sampling to assess urethane levels is a formidable task.

Evidence suggests that bourbons - because of the type of distilling process required - generally contain the highest levels, while vodka and gin have negligible amounts. Levels in plum and cherry brandy have varied from 200 to 12,000 parts per billion (ppb); in dessert wine from less than 4 to several hundred ppb, and in table wine, 0-25 ppb.

Manufacturers are experimenting with alternating production methods that will reduce urethane levels in finished products. And they have set time goals for reducing urethane content. Both the FDA and ATF are working with foreign countries to lower the urethane levels in imported beverages.

But while this burst of effort is under way, we have yet to quantify the risk to humans. In 1988, the National Toxicology Program agreed to give the problem of urethane its highest priority, to better define potential hazards.

QUESTION - Can you explain why overbeaten egg whites become stiff and dry and look almost curdled?

ANSWER - The effect you describe is caused by changes in the structure of surface proteins in the film surrounding the air cells. These changes render the egg whites insoluble and inelastic. The protein in overbeaten eggs behaves as though it had been cooked.

Adding sugar, as you would do in making a meringue, creates a more stable and shinier foam. This shininess is due in part to preventing the coagulation of the protein. The addition of sugar makes it possible to beat egg whites for quite a while longer without producing undesirable changes. Foam beaten alone must be used at once or will break down, but when sugar is included, the foam (or meringue) can stand for some time without deteriorating.