In the early 19th Century, the development of longer-lasting, bottom fermented lager beers, and technological advances in brewing and bottling machinery, made it possible to produce and distribute beer on a large scale.  The only problem lay in quality control – often the beer would turn sour during production or transportation.

Louis Pasteur (1822-1895) had already solved similar problems for wine makers through a heat treatment process.  In the 1870s, he began studying the brewing industry to try to help French beers become more competitive against increasing German imports.  His Études sur la bière, published in 1876, demonstrated that the yeast used for beer contained impurities, such as bacteria, moulds and various wild yeasts.  He advocated a purifying procedure using tartaric acid, but this did not prove totally successful. 
 

Cloning commenced at Carlsberg

In the new Carlsberg Laboratory, Dr Emil Hansen (1842-1909) was working on the same problem. He found that there are several types of yeast, only a few of which – the cultured yeasts – are suitable for brewing.  He developed a technique to separate out the types and form colonies of pure yeast through single cell cloning.  Working with the Carlsberg managing director, S A van der Kühle, he also designed a simple machine to propagate the pure yeast on a semi-continuous basis.

 

This process was applied in the Carlsberg breweries for the first time in 1883 and was in full production by 1885. JC Jacobsen, who was a great admirer of Pasteur, was initially unwilling to accept any theories which did not fit with the French scientist’s work.  However, during a visit to Copenhagen in 1884, Pasteur paid several visits to the Carlsberg Laboratory and supported Hansen’s findings.  Through his influence, Hansen was awarded the gold medal of the French Société d’Encouragement pour l’Industrie nationale in 1886. 

 

The basis of all brewing

Hansen’s yeast - saccharomyces carlsbergensis - was freely offered to other breweries when their yeast became infected and was soon made available around the world.  It still forms the basis of all lager brewing today.