Pickles in a flash—not too bad, right? Officially, these aren’t true pickles, a term reserved for foods that are fermented with acid-producing bacteria.
What you’ve really done here would be more properly called flash marinating: rapidly infusing brine into food with the help of a pressure drop. As you might suspect, the secret to the trick lies in extracting the gases that are hiding within the veggies.
Like us, plants must exchange gases with the environment to survive: carbon dioxide in and oxygen out for photosynthesis; oxygen in and carbon dioxide out for cellular respiration. Unlike us, however, plants don’t have lungs or any other fancy gas transport systems. Instead, they “breathe” mainly via passive diffusion of gasses through a network of nooks, crannies, and tiny tubules found in the spaces between cells.
It’s these hidden pockets of “plant breath” that form the bubbles that appear in the syringe when you pull hard on the plunger. The extreme low pressure you create causes the gas pockets in and between the cells in the veggies to expand—courtesy of Boyle’s Law—and burst free from their membranes. When you release the syringe and the pressure increases around the submerged vegetables, liquid gets pushed back into the spaces where the air had been, infusing the vegetables with brine.