Another reason why taste is impaired with age is the structural change of taste nipple. These uneven structures carry taste buds on the mouth, tongue and palate. There is a kind of mastoid called fungal mastoid, which contains many taste buds. With the increase of age, its number will also decrease, and its shape will change and become more closed. The more open the mastoid is, the easier it is for chemicals in food to come into contact with receptors to produce flavor. Closed nipples reduce the contact surface between food compounds and receptors, resulting in reduced perception of food taste.
With the increase of age, saliva secretion will also decrease. This means that there is less liquid to transport the food compound to the taste receptor and less liquid to help the food compound dissolve, so the taste is unlikely to be triggered. When our sense of smell is weakened and we can't detect and distinguish different smells, it will affect our taste. There are several reasons for the decline of olfactory sensitivity with age, including the decrease in the number of olfactory receptors (recognizing different odor molecules) at the back of nasal cavity and the decrease in the regeneration rate of receptor cells.
Moreover, with the increase of age, the taste nerve becomes easily damaged, and the taste nerve is damaged or missing: after the taste nerve is damaged or missing, the taste neurons of taste buds lose nerve stimulation conduction, which may have an impact on taste. The short-term behavior observation after bilateral chorda tympani nerve resection found that the hamster's taste sensitivity to sucrose and salt changed obviously, while the long-term behavior observation found that the change was not significant, suggesting that there may be negative feedback mechanism rather than direct control of taste nerve.