One of the most frequent questions from readers is how long can you keep wine once a bottle is opened? Air is both the friend and enemy of wine. On opening, exposure to air (breathing we call it) releases aromatics in the wine, improving its aroma and ultimately its flavor. But, with prolonged exposure to air, wine becomes dark, rancid and undrinkable. While there are many variables involved in how long an open bottle will last, the most important seems to be color. If properly stored, red wines may last as long as three days. White wines, on the other hand, may last as long as six or seven days. Another important variable is how much wine remains in the bottle; the more wine in the bottle the longer it will last. If only an inch or so remains, it can spoil overnight. Refrigeration and removing air from the bottle are two ways of maximizing the length of time a wine will remain drinkable. There are a couple of methods available for removing air from an open wine bottle. The simplest is pumping the air out. There are several products in this category, but the cleverest is simply a bottle-stopper with a pump mechanism on its top. Stopper the bottle, pump it a few times and you’re done. The other method involves replacing the air in the bottle with Nitrogen, an inert gas that doesn’t react with the wine. This involves squirting Nitrogen gas from a can into the bottle, forcing the air out. I personally think this is the more effective of the two methods, but it is also the most expensive. The cans of gas are surprisingly expensive and don’t last that long. Since one can of Nitrogen should be as good as another, look for the brand that gives you the most gas for your money.   After you have removed the air, the next step in preserving an open bottle is refrigeration. Refrigeration slows the chemical processes going on in the wine, prolonging its drink ability. Your refrigerator will cool your red wine well below optimal drinking temperature. And, while a little chill on a red wine will bring out its fruit, too low a temperature will render it flat and uninteresting. So, be sure too allow red wine to warm to around 60 degrees before you serve it.   Wine does not go bad all at once. It goes gradually over the period of days. So when you taste the wine on the second day it won’t be completely spoiled but it will not be as pristine as it was the day before. You will detect spoilage first in the aroma and then in the taste. You will know when to dispose of it. There is no mistaking the smell and taste of wine spoiled by exposure to the air. Some describe it as tasting like cheap sherry; others like burnt raisins; either way it is very distinctive. The wine’s color also changes. White wines become darker, red wines more amber. You may also detect this unpleasant aroma, taste and color in wine you order by-the-glass at restaurants. If you are unlucky enough to get the last of a bottle opened two days ago, chances are it is spoiled. Don’t be bashful, send it back. - Cellar Notes - A number of readers have expressed interest in Riesling [REES-ling]. Riesling (aka Johannesburg Riesling and White Riesling) is a white wine, originally from Germany, made in a range of styles from dry to very sweet. The riper the grapes are allowed to become before harvest, the sweeter the resulting wine. In general Rieslings tend to be fruity, with apple, peach, pear, and floral aromas.   German Riesling is labeled using regulated terminology. The driest Rieslings are labeled “Kabinett,” those just a bit sweeter “Spatlese,” and those much sweeter “Auslese.” Rieslings labeled “Beerenauslese” or “BA” and “Trockenbeerenauslese” or “TBA” are respectively very sweet and extremely sweet and are classified as desert wines. If you didn’t take German in high school, don’t worry about the pronunciation of these terms, just look for them on the label. American and other non-German Rieslings do not have this uniform labeling standard. For these, the back label may give you an idea of sweetness. Absent any information, you can reasonably assume these wines will be dry or almost dry (Kabinett or Spatlese). Rieslings are very versatile with food. The dryer (Kabinett and Spatlese) styles are superb with sautéed, broiled or grilled seafood, most pork, poultry and veal dishes and many Asian dishes. The sweeter (Auslese, BA, TBA) styles can be considered deserts in themselves, but also compliment moderately sweet deserts that contain tart fruits.   Here are three examples of Riesling, under $10. The German wine is Spatlese. The two American wines are somewhat sweet, but less so than the Spatlese. Serve well chilled. Eroica Riesling – White Varietal • Chateau Ste. Michelle • Washington State • Spec $15 - $20  Johannesburg Riesling – White Varietal • Mondavi Private Selection • Monterey County • Specs $5 - $10  Riesling Spatlese – White Varietal • Bergman • Germany • Specs $5 - $10    Local oenophile David Dickson has been enjoying, learning, and teaching about wine for nearly 30 years. He welcomes questions, comments and suggestions for columns at This email address is being protected from spambots. You need JavaScript enabled to view it.. Visit his Web site at www.lifeisacabernet.net.