We expect something to taste a certain way by how it smells, and the smell is interpreted by our brain along with our taste buds. When you have a cold, you will notice that things taste differently or do not taste at all. This is because you cannot smell them.
Smell has a lot to do with the subtleties of taste. Tasting food really has three components. One is the chemical taste sense, which comes from the taste buds on your tongue, and which can detect only sweet, sour, salt, bitter, and umami (a protein taste). The second component is "mouth feel", or texture. All the rest of your sense of taste really comes from your sense of smell. You can detect only five tastes, but you can detect and identify thousands of smells.That's why losing your sense of smell, either temporarily during an illness, or permanently, makes food seem rather tasteless.