A person cannot taste food unless it is mixed with saliva. For example, if a strong-tasting substance like salt is placed on a dry tongue, the taste buds will not be able to taste it. As soon as a drop of saliva is added and the salt is dissolved, however, a definite taste sensation results. This is true for all foods. Try it!
Chemoreceptors in the taste buds of your tongue require a liquid medium in order for the flavors to bind into the receptor molecules. If you don't have liquid, you won't see results. Now, technically you can use water for this purpose rather than saliva. However, saliva contains amylase, an enzyme that acts on sugars and other carbohydrates, so without saliva, sweet and starchy foods may taste different from what you expect.
You have separate receptors for different tastes, such as sweet, salty, sour, and bitter. The receptors are located all over your tongue, though you may see increased sensitivity to certain tastes in certain areas. The sweet-detecting receptors are grouped near the tip of your tongue, with the salt-detecting taste buds beyond them, the sour-tasting receptors along the sides of your tongue, and the bitter buds near the back of the tongue. If you like, experiment with flavors depending on where you place the food on your tongue. Your sense of smell is closely tied to your sense of taste, too. You also need moisture to smell molecules. This is why dry foods were chosen for this experiment. You can smell/taste a strawberry, for example, before it even touches your tongue!