Just for the sake of curiosity, if you put your tongue on a 9-volt battery, you would get a slightly painful shock that almost resembles sour taste, kind of like lemonade. Why does that happen?  Well, here’s what goes through your tongue when you lick a 9V battery and why that shock has a flavor.

Touching those little knobs or leads of a 9-volt battery won’t give you a shock because the skin is not that good of a conductor of electricity and it can’t cause current to flow. But, on the other hand, if you touch them with your tongue, the saliva promptly completes the circuit.

When you place your tongue on a battery lead, your saliva causes the electrons from one end of the lead to start moving to the other, creating an electric current.

Moreover, the electrons, on the way, interact with water molecules and break them down in a process called electrolysis. The current entering the saliva from one end of the lead produces hydrogen, leaving hydroxide ions behind. And the current leaving the saliva through the other lead produces oxygen and also leaves hydroxide ions behind. These hydroxide ions (acid) are what activate the sour receptors.

Well, not all currents taste the same. Because different taste receptors can be stimulated with the right combination of current and temperature – a phenomenon called electrical taste. So smaller shocks can be sweet, spicy, bitter or even savory at times.  What this means is that anyone can be tricked into tasting all kinds of flavor by meddling with the strength of the current, the temperatures, and associating the shocks with artificial smells or lights.

In 2016 study, scientists were able to make plain water and plain porridge taste sour, bitter, or savory using a spoon and a bottle. The spoon and the bottle were specially designed to send weak and controlled electric pulse on the tip of the tongue and stimulate different taste sensations. They also incorporated an RGB Light Emitting Diode (LED) into the bottle to change the color of water.

Well, electrodes can’t recreate the taste of all your favorite food yet, but stimulating the same type of taste receptors can give you a stronger perception of the taste. After all, the flavor of the food you eat is determined in your brain. It can be affected by your cutlery or the music you play while you eat.

Why do batteries taste sour? When you lick a battery, your saliva causes the electrons from one end of the lead to start moving to the other, creating an electric current. The electrons also interact with water molecules in a process called electrolysis, which produces hydrogen and oxygen gases. The reaction also gives out hydroxide ions which activate the sour receptors, giving you a slightly sour taste. [SciShow]