When was the last time you had a truly bad bottle of wine? Not one that you just didn\u2019t like, but one that stank?\r\n\r\n\u201cCorked\u201d bottles are the most common today, and bottles that taste \u201ccorked\u201d but really went bad for other reasons. It used to be common to open a funky-smelling or stale wine, or a fizzy wine that wasn\u2019t supposed to be sparkling.\r\n\r\nThank god and the world\u2019s winemaking universities that we don\u2019t have to put up with many truly flawed, terrible wines anymore. But it does still happen. In the last few weeks I\u2019ve had a very barnyardy Chambourcin and an otherwise nice Chardonnay that seemed to have a veneer of burnt rubber.\r\n\r\nHere\u2019s what I know about telling the difference between a wine that just doesn\u2019t suit you and one that should be poured down the drain. If you buy a bottle in a restaurant or from a retailer that has any of these flaws to a noticeable degree, then you should ask the sommelier to take it back, or return the bottle to the store.\r\n\r\n\r\n\r\nCorked\r\nThe most common flaw in wine comes from a defective cork that infects the wine and turns the aroma to a mildewed, wet-cardboard smell and the taste to a flattened, dried-out sensation. The wine is called \u201ccorked\u201d or \u201ccorky.\u201d You should send it back in a restaurant or ask the wine merchant who sold it to you to exchange it for a good bottle.\r\n\r\nTCA infected\r\nTrichloroanisole is the compound that makes the corky smell. But it doesn\u2019t just come from cork. It can grow in a winery on any material made of cellulose, including barrels, wood building parts, cardboard boxes, even rubber hoses, if there\u2019s also chlorine present. Often times we blame the musty smell on the cork, when something else caused the problem.\r\n\r\nBrettanomyces\r\nBrett and its cousin Dekkera are undesirable yeasts that are difficult to keep out of wine. Some winemakers and critics like the smoky, leathery aromas that Brett can add in small doses. But when it goes too far you\u2019ve got a pungent problem on your hands. It smells like cow dung or rubber boots and Band-Aids. I think that consumers in general are going to turn against this and demand none of it in their wine in the future.\r\n\r\nOxidized\r\nThe oxygen in air makes a good wine go bad in a day or two if an opened bottle isn\u2019t properly looked after. An oxidized wine smells to me like stale bread or weak vinegar (which it\u2019s trying to turn into). This is a particular hazard with wines by the glass at restaurants, where half-empty bottles are often kept on the bar overnight. Refrigeration helps, even for reds. Another preventive measure is pouring the wine into a smaller container like a half-bottle (375 milliliter) with a tight lid so that it fills to the top and excludes any air.\r\n\r\nCooked\r\nWine can be \u201ccooked\u201d if kept in hot attics or trunks, above stoves or in frugally minded corporate offices where the AC is turned off over the weekends. It\u2019s a slow simmer, but the wine gets ruined before long. It will look brownish around the edges of the glass (whether red or white) and may smell caramelized, like cooked onions. If you also noticed that the cork in the bottle was pushed up and partway out, it\u2019s probably cooked.\r\n\r\nGoing through malolactic\r\nWinemakers put most red wines and many whites, especially Chardonnay, through a mild secondary transformation in addition to the yeast fermentation. The conversion is called malolactic, or ML. But if a winemaker isn\u2019t careful, the malolactic can happen after the wine is bottled. The result can vary from a mild effervescence to a totally stinky aroma and bizarre flavors. One frequent sign is an unusually cloudy or hazy appearance.\r\n\r\nSulfury\r\nSulfur dioxide is added to virtually all wines in small quantities (10 to about 100 parts per million) to help prevent oxidation and bacterial growth. That\u2019s why you see the note on the label that says \u201cContains Sulfites.\u201d Sulfur is a good thing in moderation, but if the winemaker goofs and adds too much, then the wine smells like matchsticks and can prickle the inside of your nostrils. It\u2019s not wise to drink it. Another wrinkle on the sulfur problem is when a wine smells like rotten eggs. This is from hydrogen sulfide that can develop during fermentation and aging.\r\n\r\nHow often have you encountered one of these, and what did you do about it?