Every dish is made up of several ingredients and flavours that interact to create a delicious whole.
Wine is exactly the same way. When food and wines combine in your mouth, the dynamics of each change, the result is completely individual to each dish-and-wine combination.
When wine meets food:
The food can exaggerate a characteristic of the wine. For example if you eat walnuts (which are tannic) with a tannic red wine, such as Bordeaux, the wine tastes so dry and astringent that most people would consider it undrinkable.
The food can diminish the characteristic of the wine. Protein diminishes the impression of tannin, for example, and an overly-tannic red wine – unpleasant on its own – could be delightful with rare steak or roast beef.
The flavour intensity of the wine can obliterate the wine's flavour or vice versa. If you have ever drunk a big rich red wine with a delicate filet of sole, than you have had firsthand experience of this.
The wine can contribute new flavours to the dish. A red zinfandel that's gushing with berry fruit can bring its berry flavours to the dish, almost as if another ingredient has been added.
The combination of wine and food can interact perfectly, creating a sensational taste experience that is greater than the food or the wine alone.
Fortunately what happens between food and wine is not haphazard. Certain elements of food react in predictable ways with certain elements of wine, giving us a fighting chance at making successful matches. The major components of wine (alcohol, sweetness, acid and tannin) relate to the basic taste of food (sweetness, sourness, bitterness and saltiness) the same way that the principle of balance in wine operates: Some of the elements exaggerate each other, and some of them compensate for each other.
Here are some ways that food and wine interact, based on the components of the wine. Whether a wine is considered tannic, sweet, acidic or high in alcohol depends on its dominant component.