So what's going on inside that banana?
In this experiment we have both water (H2O
) and Vodka (ethanol
Because the peel of the banana is a semi permeable membrane
, it allows the ethanol to pass through it. This is caused by the difference in the concentrations of salts
inside and outside the peel.
High concentration of potassium
and other salts
inside the banana and the low concentration of salts outside the banana will encourage the ethanol to pass through the peel into the banana to equilibrate
According to an article in Experimental Botony, 1980, volume 31, number 4, pages 975-982, the banana pulp will begin to leech electrolytes
. The high concentration of potassium inside the banana will drop. This will also help the system come to equilibrium.
The coagulation of the inside of the banana is readily dependent on the temperature of the system.
Ethanol is a great solvent for biological molecules. It will dissolve some of the inside of the banana, but at the same time all the lipids
will not go into solution. So it is no surprise that the ethanol makes the banana become 'softer.' It is essentially liquefying the inside.
In the process, the transition temperature inside the banana has raised above the temperature in the refrigerator. Dropping the temperature will cause the lipids and the ethanol solution to congeal
Hence the 'gel-o-shot' like state.
For more information regarding Osmotic Pressure and Ionic Equilibrium, here are a couple of great books on the subject. (Via amazon.com)The Osmotic Pressure of Biological Macromolecules by M.P. Tombs & Arthur R. PeacockeIonic Equilibrium: Solubility and pH Calculations by James N. Butler