The olfactory and gustatory nerve cells, which govern smell and taste respectively, are very closely related. This close relationship becomes especially evident when undertaking a science fair project to quantize it. There are many different projects one can set up to determine exactly how smell affects taste, but all of them require a few specific criteria be met to yield the best results. Heed these guidelines and properly research and you will be on your way to having a comprehensive science fair project on smell affecting taste.
Writing a hypothesis outlines your project's goals and predicts what the end result of the project will be and is commonly written as an "if-then" statement. For example: "If I limit my subject's olfactory senses, then they will have an altered sense of taste." The hypothesis need not be specific or unique, but it must be testable.
Clearly outlining your variables will allow you to better understand your results. For a science fair project on smell affecting taste, you should have at least one independent variable and one dependent variable. Usually the phrasing following the "if" of the hypothesis' "if-then" statement will be your independent variable. For the earlier example, the limiting of the test subject's olfactory senses -- ability to smell -- is the independent variable, as you can directly control it. It will affect what they taste, which is the dependent variable.
Food or some non-toxic object which can be ingested should be at the top of the list for materials. In addition, you should use nose plugs or clamps to limit the subjects' ability to smell. You can also extend your hypothesis and limit other sensory organs, such as touch and sight by requiring goggles and gloves for your subjects.
Outline your procedures, making sure that they can be used to test fairly. Determine your ideal subjects, specific foods and limitations in each round of testing, and chart the results in the same way.
Carry out at least one experiment using your procedures. Be sure to remain fair during the experimentation for the best results, and don't deviate from the procedures if possible. Even simple things, like the pacing at which subjects eat, can throw off results because of the way dissolving food can pass between the back of the throat up into the nose, which affects taste. Slower eaters who chew more will probably have more taste for this reason.
After performing at least one experiment using your Procedures, you will be able to form a conclusion. This can be as simple as the validity of your hypothesis -- whether it was correct or incorrect -- but further explaining why you think these conclusions were reached will aid others who repeat the project or read about it.