Louis Pasteur’s pasteurization experiment illustrates the fact that the cause of liquid to spoil was caused by particles in the air rather than the air itself.
Pasteur conducted multiple experiments proving his theory, one of which is the swan flasks. Pasteur had boiled broth and placed in into two separate flasks, The first flask had a swan neck attached to the flask, the second one, the neck was removed, opening it up to particles. He then waited and noticed that the flask with no neck had already spoiled while the swan necked flask was still fine. Thus concluding that it was the particles spoiling liquids not the air itself.