Quickly fit the pointed end of the half-banana downwards into the bottle neck so that it makes an airtight plug. When the banana is placed into the mouth of the bottle and the cooling air inside the bottle shrinks again, the air pressure inside is reduced, and the greater air pressure outside shoves the banana ahead of it into the bottle. Just small differences in air pressure can cause things to move. Just wait a few days. Let the bacteria in the banana do their chemistry work.
Bacteria give off enzymes that break down proteins and starches.
Top of Page References Reprinted with permission from the Ohio Chemistry Technology Council, TIE 1999 Handbook.