Dutch lens maker Anton van Leeuwenhoek was probably the first person to see yeast. He made this drawing in 1680, after viewing beer through his primitive homemade microscope.

Bacterial filters were an essential tool for securing a supply of uncontaminated water and for purifying products in industrial applications. This porcelain filter, developed in Pasteur’s laboratory, had tiny pores that allowed fluids to pass through while holding back bacteria and other microorganisms.

Brewing handbooks described the tools and techniques needed for the study of yeasts and bacteria encountered in the brewing process.

Lactic-acid bacteria, a major cause of spoilage in the brewing process, are shown growing on a variety of culture media. Brewing handbooks described the tools and techniques needed for the study of yeasts and bacteria encountered in the brewing process.

These culture tubes were used to grow microbes for identification. They contain a special preparation of nutrients in a jelly-like base. A sterile instrument like the swab was used to transfer the test substance to the tube.

An illustration in Pasteur’s book shows what healthy and worn-out yeast cells look like when viewed through the microscope.

Pasteur used special tools and methods for studying the activity of microorganisms in the brewing process. Flasks with long curved necks allowed oxygen to get in while keeping unwanted microbes out. Improvements in microscope lenses made the identification of different microorganisms possible.

Pasteur published the results of his study of beer-making as Études sur la Bière in 1876. This illustration from his book demonstrates a method for examining the yeast in beer without exposing the sample to contamination from other microorganisms. His publication included plans for a fermentation tank that would prevent air-borne bacteria from entering and spoiling the brew.

Pasteur’s work is celebrated as laying the foundation for the science of bacteriology. His investigations on the behalf of French industry established tools and techniques necessary for controlling the productive and destructive power of microorganisms.

Beer making is an old technology that relies on microorganisms. Brewers, however, barely knew of the existence of microbes, much less the critical role they played in their livelihood. Problems encountered in beer production, motivated scientists to study the secrets of this “invisible world.”

In the mid-19th century, chemist Louis Pasteur worked with French beer makers to discover what was causing their product to spoil. Through his investigation into the “diseases” of beer, Pasteur demonstrated the essential role that yeast, a tiny living organism, played in the fermentation process and identified microorganisms that caused beer to go bad.

Breweries, as well as other fermentation based industries, adopted new scientific tools and techniques in order to better control the productive and destructive power of microorganisms.