Taste and olfaction are considered chemosenses as they involve the detection of chemicals in our environment. Beyond this distinction, they are closely linked. To understand this connection one needs only to think of the last time they had a stuffy nose. With your sense of smell diminished it was likely you noticed how bland food tasted. Olfaction requires that odor molecules reach the nasal cavity and pass over receptor fibers either originating from the nose or mouth. This processes significantly contributes to the flavor we perceive.
Orthonasal Olfaction: When someone is cooking breakfast, you can often recognize the aroma of fresh coffee, toasted bread, and (if lucky) bacon before you step foot in the kitchen. When breathing through our nose we draw odorants over our olfactory receptors. You may find your self unconsciously inhaling deeply when you enjoy the smell or suddenly breathing through you mouth (and maybe pointing fingers) when you encounter an unpleasant odor. This also helps us to determine whether food is safe to eat.
Retronasal Olfaction: As we masticate (chew) food odorants from the food make their way through the back of our throat over our olfactory receptors. This greatly enhances our ability to experience and distinguish different foods.
Demonstration 1: Hand out pieces or whole Fruit-by-the-Foot snacks (strawberry flavor) to your participants. Have everyone open the packaging, pinch their nose, and begin eating the snack. Ask the students to slowly chew the food, noting the flavor while keeping their nose blocked. Next, have them release their noses so they can experience the effect of retronasal olfaction. They should notice a dramatic increase in the flavor they perceive.
Demonstration 2: We identify foods based on their appearance, texture, taste, and smell. By limiting the number of senses we can bring to bear, our sensitivity will decrease, often dramatically.
Cut up the following foods into equal size cubes.
Apple, potato, sweet potato, pear, onion, jicama, melon, and strawberry.
Blindfold or have the participants close their eyes during the taste test. Do not allow them to see what foods are being used or have been used during the experiment. Using plastic forks, allow the students to eat each item, noting their response. You can make this more difficult by requiring them to hold their nose.
Demonstration 3: Use solutions of different concentrations containing: lemon juice, sugar, salt, tonic water, and monosodium glutamate. Make a starting solution that you can clearly taste, but isn't too strong. Make serial dilutions, taking half the total volume and an equal amount of water. Repeat this process until the resulting solution taste no different than plain water. Mark the solutions so that you know the flavor and concentration of each solution, but hide this from you students. Randomly present the solutions, asking the whether the subjects detect a flavor and if so then can they identify it as sour, sweet, salty, bitter, or savory (umami).