The Treatment of Brewing Yeast

By Anon Anon

Four experts in the field write about yeast. Contents Include: A History of Yeast Treatment; Yeasts and the Brewery; Routine Measurements of Yeast Fermentation; Features of Various Yeast Species; Simple Photomicrography. This book contains classic material dating back to the 1900s and before. The content has been carefully selected for its interest and relevance to a modern audience.

• Language: English
• Publisher: Read Books Ltd.
• Release date: Aug 26, 2016
• ISBN: 9781473353411

Book preview

PART I

A HISTORY OF YEAST

TREATMENT

By S. PETER COLE

1. T HE D AWNING

2. T HE Y EARS IN D ARKNESS

3. P ASTEUR ’ S M ETHODS

4. P URE C ULTURE S YSTEMS

5. A CID T REATMENTS

6. S OME O THER M ETHODS

7. W HAT IS THE I DEAL ?

1. THE DAWNING.

Every unhealthy change in the quality of beer coincides with a development of microscopic germs which are alien to the pure ferment of beer.

The absence of change in wort and beer coincides with the absence of foreign organisms.

These quotations are from Pasteur’s Études sur la bière, the product of his brilliant work on the spoilage of beer by micro-organisms. The scientific world of the time was astounded by his discoveries, which were probably the first major scientific contribution to the Art of Brewing. While we may challenge the absolute truth of Pasteur’s beliefs in the light of modern research, we cannot deny that the development of foreign organisms in pitching yeast can only lead to a deterioration of the final beer quality. The purpose of this part of the book is to trace some of the methods which have been employed to obtain, and maintain, a pure pitching yeast, since the time of Pasteur.

2. THE YEARS IN DARKNESS.

By the middle of the last century the subject of beer spoilage had become of great importance on the Continent, and to a lesser degree in this country. The brewing industry in France was almost overwhelmed by the problems of a beer which would not keep. The problem was made more intense by an extremely fluctuating trade, the French having always considered beer to be primarily a warm weather drink. The comparatively sudden change from top to bottom fermentation brewing on the Continent was a great help to French brewers. By keeping their beer at low temperature in the brewery, they were able to hold much larger stocks with less risk of spoilage.

One wonders whether this change was entirely dictated by palate. Pasteur was convinced that it was not. He compares the complications of the bottom fermentation process with the relatively simple operations of the older method of brewing. He then asks, Why should a mode of brewing so simple, so rapid, and comparatively so inexpensive, have been abandoned by the greater part of Europe in favour of a system disadvantageous to the brewer in so many respects? It would be a mistake to suppose that the sole reason for such a change might be found in the superior quality of low beer.

The ten years between 1860 and 1870 saw an almost complete change-over to the bottom fermentation process in French breweries. Although this new method of brewing allowed the industry to continue, the costs that it involved were slowly strangling its operations. Approximately two and a half hundredweights of ice were required for each barrel of beer from the time of brewing to consumption.

In this country the picture was a little better, though by no means was it a happy one. By dint of great care in the fermentation process, British brewers succeeded in producing a beer which was superior in keeping qualities to most Continental top fermentation beers. No doubt the higher gravities of those days helped in some measure, also the trade was far more consistent on this side of the Channel. It is interesting to note that not one British brewery changed to the new process during the time mentioned above. We may not deduce from this, however, that our beers were free from spoilage organisms; Pasteur’s accounts of his visits to breweries in this country show that some of our pitching yeasts were far from pure.

Since the necessary knowledge was not available it is not surprising to find that there were few effective methods of purifying yeast at that time. The French washed their yeast with water and stored it under ice, the storage period being as short as possible. This undoubtedly prevented any excessive infection during storage, but it can have done little towards removing those infecting organisms already present. British brewers appear to have had no standard method, each brewery evolving its own treatment as necessary, by trial and error. Everywhere the practice of the changing of pitching yeast was in common use, the frequency of these changes being decided by numerous and bizarre systems. Some brewers considered themselves wedded to their yeast for better or for worse, while others changed theirs with the seasons. Probably the most original system was that of the politically-minded gentleman of Bohemia, who was reputed to change his yeast with the advent of a new government. He would have been a bewildered gentleman indeed had he and his system survived to the present day!

It is at this point that Pasteur’s name first appears in the pages