Below are the problems you can easily determine by looking at the COLOR, by the SMELL and TASTE.
* Red brick or brown shades. This means that the wine is spoiled due to oxygen contact. If this is not a bottle from the 90s and is only a few years old, feel free to take it back to the store.
* Slight murkiness. Now filtering wine has become unfashionable, it is believed that unfiltered wine tastes better. Biodynamic, Organic and Natural Wines are examples of this.
* Orange shades in sherry and wines older than 5 years old.
* Small diamond like crystals at the bottom of the bottle. These are tartaric acid salts. In order not to confuse buyers, winemakers sometimes remove these through a process of cold stabilization and get rid of such sediment, but not always.
Take your glass by the stem and give it a whirl to saturate the wine with oxygen and let it open up.
* The smell of damp cardboard is a cork disease called TCA. This wine should not be drunk. Therefore, it is better to return to the wine shop.
* The smell of mushrooms or match sticks. This wines sulfur content didn’t bond to the wine. You can pour into a decanter and let the wine breathe for 1.5-2 hours. You can also throw a copper penny into the decanter to "collect" the sulfur, and the sulfur smell will dissipate.
* Rotten fruit and decay- If your wine smells like sherry but it’s not a sherry, it has been exposed to too much oxygen (oxygen saturation). The wine was stored incorrectly or the cork allowed in too much air.
* The smell of raw meat and blood is quite normal for saturated Reds: Australian Shiraz, Cabernet or Rioja.
* The smell of gasoline in Rieslings
* The smell of the cat pee is a feature of some Sauvignon Blanc.
* Strong bitterness. This is a sign of oxidation, or premature aging.
* The taste should not be acetic or nail polish remover. If so the bottle was kept warm for a long time.
* Taste, pleasant, without alarming things.
P.S. it is Important to try wine at the correct temperature. If its too cold all notes are hidden, in too warm alcohol the alcohol is too pronounced. Chill your reds for ½ hour in refrigerator before drinking, and whites for 2 ½ hours.