How Pasteurization Works

By: Carol White

History of Pasteurization

At that time, scientists thought that fermentation was a purely chemical process. Pasteur's research into fermentation led him to the discovery that it was yeast, a living organism, that turned the beet juice into alcohol. Under the microscope, yeast was round and plump. But when the alcohol spoiled, it contained a different microbe that was rod-shaped. Pasteur speculated that this rod-shaped microbe called Mycoderma aceti, which is commonly used to make vinegar, caused the wine to spoil [source: Feinstein].

These discoveries formed the "germ" of Pasteur's germ theory of fermentation. Years later, Pasteur would apply the same concepts to the origins of disease, leading to some of his greatest contributions to science and medicine.

In the meantime, Emperor Napoleon III enlisted Pasteur to save France's wine industry from the "diseases of wine" [source: Lewis]. In previous experiments, Pasteur had discovered that heating the fermented wine would kill the microbes that caused it to spoil. He wasn't the first to see that connection. Nicolas Appert, the inventor of in-container sterilization, also known as canning, had already shown that treating food with heat could preserve it. Pasteur's contribution was to determine the exact time and temperature that would kill the harmful microorganisms in the wine without changing its taste. He patented the process and called it pasteurization. Before long, the process was also used for beer and vinegar. 

This understanding of the role of bacteria helped him to develop his germ theory of fermentation. Years later, he became interested in human disease and applied his knowledge of microorganisms to develop the germ theory of disease. Eventually, he developed the vaccines for chicken cholera, anthrax and rabies.