Salt is composed of sodium chloride. When salt is broken down by saliva, it undergoes dissociation into Na+ and Cl-.
Na+ will be our hero in this process. Although it seems like our taste buds are always on they operate using something called the action potential. These potentials are present in neurons throughout our brain and spinal cord, as well as in our taste receptors and other cells.
These cells have an electrical current flowing through them, maintaining a constant charge of -70mV within their interiors.
If positively or negatively charged ions enter the cell, this charge can slightly fluctuate but this doesn’t really matter. If the cell’s polarity, also known as the charge, increases or decreases slightly, there are no significant consequences. However, if the cell experiences enough depolarization (i.e., if its charge is sufficiently elevated), it reaches a point of irreversibility, which is -55mV.
This is where it gets exciting!
- Once the point of no return, also referred to as the threshold stimulus or simply the threshold, is reached, an action potential is reached. This entails a sudden increase in charge, causing the cell to rise to a value exceeding +40mV!
- This charge causes a chain reaction where the charge spreads to neighboring cells. The electrical impulse traverses the body and ultimately reaches the brain, where it is interpreted as “hey, something is being touched/smelled/tasted!”
- After firing an action potential, cells return to their regular -70mV baseline and, following a brief refractory period, they are prepared for subsequent activity.
Food has an electrical stimulating effect on taste cells, elevating them to the critical level at which they become highly responsive and transmit abundant messages to the brain. Remember about salt dissociating into Na+ and Cl-?
Well, due to Na+’s positive charge, it effectively raises the baseline voltage of the receptors on our tongues. Instead of being at -70mV, they may hover around -65 or -60mV. Consequently, they require less stimulation to reach the critical -55mV threshold and transmit signals to the brain. As a result, foods taste more intense and flavorful because our taste buds are primed and swiftly respond to stimuli.
Indeed, salt possesses its own flavor, but it is also accurate to say that it “enhances the flavor of food,” as it precisely accomplishes that task! Try adding a pinch of salt to sweet foods. Salted caramel ice cream? It’s a game-changer!
If someone might be curious as to why the negative charge of Cl- does not simply negate the positive charge of Na+. The explanation lies in the fact that the resting potential (the aforementioned -70mV) is regulated by the concentration of Na+ and potassium (K+) inside and outside the cell. Cl- does play a role, but it comes into play a bit later