The sense of touch, whether it operates inside the mouth or through the fingers, conveys to us a food’s texture, consistency, astringency, and temperature. Texture is a combination of perceptions, with the eyes giving the first clue. The second comes at the touch of fingers and eating utensils, and the third is mouth feel, as detected by the teeth and tactile nerve cells in the mouth located on the tongue and palate. Textural or structural qualities are especially obvious in such foods as apples, popcorn, liver, crackers, potato chips, tapioca pudding, cereals, and celery, to name just a few. Textures felt in the mouth can be described as coarse (grainy, sandy, mealy), crisp, fine, dry, moist, greasy, smooth (creamy, velvety), lumpy, rough, sticky, solid, porous, bubbly, or flat. Tenderness, which is somewhat dependent on texture, is judged by how easily the food gives way to the pressure of the teeth. Consistency is only slightly different than tenderness, and is expressed in terms of brittleness, chewiness, viscosity, thickness, thinness, and elasticity (rubbery, gummy). Astringency is believed to be caused by the drawing out of proteins naturally found in the mouth’s saliva and mucous membranes. Foods such as cranberries, lemon juice, and vinegar have astringent qualities.
The temperature of a food also affects the perception of it. Most people appreciate a hot meal, but extremely hot temperatures can literally burn the taste buds, although they later regenerate. The other kind of “hot” that may be experienced with food is the kind generated by “hot” peppers. The hotness in peppers is produced by a chemical called capsaicin (cap-SAY-iss-in). Many people enjoy the sensation of capsaicin in moderation, but it can cause real pain because it is a powerful chemical that irritates nerves in the nose and mouth. In fact, this compound is so caustic when concentrated that it is now used by many law enforcement agencies in place of the mace-like sprays.
The sounds associated with foods can play a role in evaluating their quality. How often have you seen someone tapping a melon to determine if it is ripe or not? Sounds like sizzling, crunching, popping, bubbling, swirling, pouring, squeaking, dripping, exploding (think of an egg yolk in a microwave), and crackling can communicate a great deal about a food while it is being prepared, poured, or chewed. Most of these sounds are affected by water content, and their characteristics thus give clues to a food’s freshness and/or doneness.