By Piero Selvaggio

Wine rituals in restaurants can be mystifying. When hosts order a bottle, they are always offered a taste to approve the wine before it is poured for their guests. Many people are confused about what they should look for when asked to judge the wine and are afraid to ask. Some are too shy to reject a bottle, worrying that to do so is rude. Others misunderstand the purpose of the sample taste, sending bottles back for little or no reason. Neither of these extremes is correct. Wine should be rejected only if it is truly bad or if it was recommended in error.

Since wine is a natural product, each and every bottle is unique. Like grapes, a few wines are imperfect. Wine can be damaged by many factors, most often faulty corks, poor storage, and accidents of winemaking. Although modern winemaking has greatly reduced the number of disappointing bottles, many reasons can cause a wine to be unfit to serve your guests.

• The reason that restaurant guests are asked to sample and approve each bottle of wine is because some bottles are defective.

Guests are given the chance to approve the bottle because something might be wrong with the wine. No restaurateur wants guests to suffer through a spoiled wine any more than a burnt risotto. It’s not good for business. If there is a problem with anything you’re served, including the wine, you should always speak up. Don’t be embarrassed. You are doing the restaurant a favor by giving them a chance to correct the situation.

• Wine can have unusual flavors and often tastes worst on first sip, so take your time and trust your nose.

Wines can seem one way alone and then change personality with food. Also, the palate takes a sip or two to adjust to wine. Don’t immediately assume that something’s wrong just because a wine has an uncommon aroma or seems too acidic. With wine, it’s always wise to pay more attention to your nose than to your mouth. Even great wines can smell a little strange—earthy or leathery or leafy and so on. Interesting smells are okay, but if a wine’s smell is unappetizing, it will rarely taste good.

• Cork taint is the most common cause for wine to be rejected; such wines are said to be corked.

No, a corked wine is not one with pieces of cork floating in it. We use this term for wines that have an offensive smell because of a bad cork, similar to that of a mildewed basement after a flood. Corks are made from the bark of a tree and can host microorganisms. Ironically, the unpleasant-smelling compound known as TCA can also be caused by treatments intended to clean the corks. Wines may be only faintly corked or badly corked, and in many cases the “good” wine aromas are suppressed. There is little agreement about what percentage of wines are corked, with estimates ranging from 1 percent to 10 percent. What is certain is that more flawed wine is drunk in restaurants than good wine is returned. So if you suspect a wine is off, ask the wine steward for his or her opinion.

• Wines that have been poorly stored or aged too long may also be compromised enough to deserve rejection.

Although this problem has become much less common, it is still possible to find bottles that are oxidized from cracked or dried-out corks. These wines may have a sour smell of rotten fruit. Wines that are past their prime, or those that have been exposed to too much heat or light, can smell tired and almost malty, a particularly common problem for half-bottles. Unpleasant smells of vinegar, roasted nuts, or burnt rubber are also signs of problems. Wines by the glass that have been open too long sometimes smell completely flat or taste of the refrigerator.

• It is rare, but possible, for an error of service to ruin a bottle of wine.

If a sommelier accidentally tops off glasses with the wrong wine, he or she should remove the bottle and bring another. The same is true if the glass neck is somehow cracked or broken when opening the bottle. • There is only one circumstance in which you should send back a wine simply because it doesn’t suit your tastes.

If you trusted the advice of a server or sommelier and the wine chosen for you is truly not to your liking, you do not need to accept the recommendation. It was your server’s duty to determine what you would like, and not just to assume you’d share his or her tastes. If your server didn’t ask you about your tastes, he or she had little to go on. Speak up right away, and your server will gladly bring a replacement.

Piero Selvaggio is founder and owner of the Valentino Restaurant Group and one of the modern fathers of Italian cuisine in America. In 1972, with limited funds and only a modest culinary background, he opened a small Italian restaurant in an unglamorous Santa Monica neighborhood. More than thirty years later, Valentino is known for its exceptional focus on wine and is one of the finest restaurants in the Los Angeles area as well as the nation. Selvaggio's hospitality family has now grown to include restaurants in Las Vegas and on the seven seas, with Crystal Cruises.

From the book "Wine Secrets" by Marnie Old, published by Quirk Books.