The origins of pure yeast culture
Production of beer using a single strain of yeast, as opposed to a mixed population, was first performed at the Gamle (Old) Carlsberg brewery in Copenhagen in November 1883. The instigator of this radical departure from custom and practice was Emil Christian Hansen, head of the Physiological Department at the Carlsberg Laboratory. Hansen’s original conception of the idea of pure yeast was that such cultures should be free from ‘disease yeast species’. It soon became apparent to him, however, that there were different strains of ‘good brewery yeast’, with different flocculating and attenuating characteristics, which gave beers of different characters. The use of only one of these good yeasts i.e. ‘that best suited to the brewery in question’ was the sense in which the term ‘pure’ became adopted. Hansen’s technique was to isolate a single yeast by serial dilution of liquid medium and grow up a culture from this. In November 1885 the first purpose-built pure yeast culture plant designed by Hansen and Soren Anton van der Aa Kühle, technical manager of Gamle Carlsberg, was commissioned. Within a few years, pure yeast cultures were being employed in breweries across the world. In his book, Practical Studies in Fermentation published in English in 1896, Hansen lists 173 breweries in 23 countries that had installed the pure yeast culture apparatus. The majority of these breweries employed bottom fermentation, but installations were also recorded in 19 top fermentation breweries in six countries, with a single-usehttps://i.pinimg.com/564x/63/29/e0/6329e0b6059cac57618523cecba57a98.jpg reported from England. In addition to these plants, Alfred Jörgensen was by then supplying 66 other breweries with pure yeast from his laboratory in Copenhagen, the experimental station in Nuremberg was sending out more than 100 samples of pure yeast annually to small Bavarian breweries and the WahlHenius was providing a similar service to more than 60 North American breweries. Thus pure culture yeast met with widening application in both bottom and top fermentation breweries.
Only in Britain did the system stumble and meet with mixed fortune. For two decades following Hansen’s innovation an at times heated public debate ensued at meetings of the Laboratory Club and its successors over the applicability of the principle of pure yeast to the production of top fermentation beers.
A stall in progress
Hansen himself spoke in London in May 1889 on his system5 and a number of papers generally favorable to the technique were given at meetings over the next few years Brewers from Combe’s brewery in London (the single English example Hansen had given for use of his culture plant) and Chester’s brewery in Manchester were particularly enthusiastic. In the former case, two strains of pure yeast were used; one for porter and stout brewing the other for pale ale. Of their nature negative results seldom get published, there is however evidence of dissent amongst the audience in the discussions of these papers. Some brewers complained of difficulty in obtaining condition in their beers with a single yeast and also of lack of flavor. It was in order to overcome these objections that in 1894 Henri Van Laer of the Ghent brewing school promoted the use of ‘pure mixed culture’ or ‘composite culture’ as it was variously termed, i.e. a culture containing a defined mixture of two different strains of Saccharomyces cerevisiae - one for the primary and another for the secondary fermentation. Soon afterward the British Pure Yeast Company was established in Burton-on Trent, with van Laer as technical director, in order to supply suitable cultures. This move met with opposition from Hansen, who had already rejected the idea on both philosophical and practical grounds, and outright hostility from Alfred Jörgensen, Hansen’s principal acolyte. As both
Jorgensen and Van Laer were in the business of supplying yeast to breweries their disagreement over matters of science may also have been tempered by commercial considerations. In a paper published in 1894, Jörgensen did, however, make the valid point that Van Laer’s system: ‘is not able to preserve the constancy of ratio between the species of which it is composed, but has to be renewed continually if wanted to keep unaltered.’ Jorgensen returned to the attack in another paper given in March 1899 in which he lamented the ‘stall in progress’ in the application of pure yeast in Great Britain and attributed it to what he stated to be the mistaken belief that English beers required a ‘particular species of yeast ... to carry through fermentation’. He asserted that he had long ago shown that this was not the case and that all that was required was to select the correct primary yeast to achieve good results. The clear inference from his paper is that British brewers were just incompetent.
Obviously stung by this, George Harris Morris, who as we shall see presently had devoted considerable effort in trying to make pure culture work, spoke critically of Jorgensen’s paper during the discussion, noting that pure culture had received ‘a great check’ and was no longer making progress in England. In April 1899, in an attempt to cool the situation, Albert John Murphy, proprietor of a firm specialising in the supply of brewery processing aids (then known as the Vanguard Chemical Company and still extant as Murphy & Son Ltd.) delivered a paper in Leeds entitled: ‘Some aspects of the pure yeast question’. He noted the pure yeast ‘storm’ and how the technique had been ‘severely assailed by most English scientists of brewing’. He went on to observe that both sides claim to have established their views by the results of very numerous and varied experiments on a practical and commercial scale as well as in the laboratory. Whilst dismissing Van Laer’s dual yeast system as impractical, he refers to secondary fermentation as a ‘vexed and complex question’. His own results led him to believe that a single yeast could give sufficient attenuation and condition, but that sometimes there was failure for no accountable reason. He seemed to tend towards the view that these failures were due to some deficiency in the condition or nutrition of the yeast rather than the absence of the correct yeast culture. To support this he reported that failures seemed mainly to be associated with Burton, whereas success had been achieved in London, Manchester, and Bradford. He tentatively suggested that this was due to a lack of potassium and/or phosphorus in Burton yeast.
He concluded that this paper ... may be taken as a plea for further investigation into the influence which inorganic elements may have upon the formation and action of enzymes, and particularly the influence of phosphorus when organically combined.
It is clear that Murphy was seeking a biochemical rather than a microbiological explanation for the conflicting evidence so far presented on the efficacy or otherwise of pure yeast.
To be continued...
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