Cork, as a natural product, can be attacked by microorganisms and certain types of fungus can penetrate the cork producing TCA which is simply unattractive odors and tastes.(In chemical terms it is 1,2,4-trichloroanisole, for any who really want to know).Even with modern techniques a good percentage of wines arrive at your table bad to some degree.The hint of this is when the taste is somewhat bitter and lacks fruitiness.
Surprisingly enough, only about five percent of wines are partially spoiled in the move process, i.e., from vineyard to home, because this process can involve thousands of miles, as we all know.A change in temperature within a corked bottle can create an air leakage because the cork has lifted in heat and cooled again.If "cooking" has taken place in the wine, you can detect it because the fruit flavor will be more a stewed prune than a berry-fresh flavor.You can double check these in the store by looking for corks above the bottle neck or liquids too low near the base of the neck.
Oxidation can occur in wine due to excessive heat or cold and incorrect humidity.Corks then tend to shrink or crack and this will cause infiltration of air into the bottle. Some air is needed if the wine is going to age over a number of years but an undesirable amount will make the wine become more like vinegar than a fine wine.It becomes quite fruitless and resembles old Maderia which is deliberately produced in open air vats.
Excess concentrations of sulphur can produce undesirable aromas and flavors, reminding one of mothballs or burnt matches.These are easy to spot.Sediments are acceptable and very, very normal in wines.Ports and older wines, even whites, will be fine when properly decanted.Crystals will form in some wines especially when chilled for shipping and storage.This can be cleared when decanted and the wine will be just fine.
In rare cases, it's possible for dormant yeasts to remain in the wine.Additional fermentation takes place over years of shipping and storage. For non-sparkling wines, this effervescence is undesirable, but easily spotted.
Manufacturing, bottling, shipping and storing techniques are much improved over the years and the odds of you running into the aforementioned problems are quite rare these days.However, if you should find one that is not to your liking, perhaps it just "isn't for you".There are many others that you will enjoy rather than this one!
