2 oo SECTIONAL ADDRESSES 



on beer, undertaken as an immediate result of the misfortunes which befell 

 France after the Franco-Prussian War, led to a scientific method of 

 brewing. It has been said that when we can convert our evening paper 

 into sugar so rapidly that we are able to eat for breakfast the albumen 

 prepared therefrom, then indeed shall we have solved one of the greatest 

 problems of the century. 



It is easy to suggest how some of the early important social discoveries 

 in fermentation were made, but Elia has immortalised the essentials of 

 all such hypotheses ; the aim of science is to confine within reasonable 

 limits the stage which corresponds to the burning down of the hut. 



Most of the older processes depend upon the action of yeasts, i.e. 

 fermentation in its restricted sense, the conversion of sugar into alcohol 

 and carbon dioxide. They make a formidable list, and it is not necessary 

 to refer to any but the more important or more interesting. 



Bread has been made since prehistoric times and leavened and un- 

 leavened bread were clearly distinguished in the Divine instructions 

 for the first Passover. Leaven is a portion of dough left over from the 

 previous baking, and French bakery had its sequence from levain de chef 

 to levain de tons points. The ' sour dough ' was presumably the 

 experienced pioneer who saved a little of his previous bake. It was a 

 great step forward when brewers' yeast was first used in baking in the 

 early eighteenth century. The purpose of fermentation is the effective 

 aeration of the dough by the uniform dispersion of carbon dioxide which 

 must be occluded and retained by the gluten so that a well-risen loaf 

 will result on baking, of required volume, texture and flavour with no 

 alteration of the wheat protein. This fermentation is now accomplished 

 by compressed-yeasts of pure-culture strains physiologically adapted to 

 rapid and abundant gas-production in the complex environment of the 

 dough. The compressed-yeast industry has gradually become more 

 scientific since its introduction about i860. For forty years or so the 

 Vienna process of low aeration was practised, but this has been long 

 replaced by higher aeration methods. The employment of compressed- 

 yeasts has supplanted the older methods of using leavens, barms, ferments 

 and brewers' and distillers' yeasts except where special types of bread 

 are required, but even here biological culture materials are coming into 

 use as for the fermentation of sour-rye dough. Chemical methods of 

 aeration such as by carbon dioxide under pressure, or as the result of 

 reaction of substances in the presence of water, have fallen into disfavour 

 except in biscuit manufacture, cake mixtures and self-raising flour. In 

 ordinary circumstances it is essential that the yeast shall be used fairly 

 fresh, and in England supplies are distributed to every town and village 

 three times a week. During the General Strike of 1926 the Board of 

 Trade had an emergency organisation which kept up the regular supply 

 from Scotland and Ireland. The amount of bakers' yeast produced in 

 Great Britain in 1930 was 2,200 tons with a value of £916,000. 



The changes which take place in the juices of fruits doubtless were 

 known before the fermentation of cereals. Certainly by the time man's 

 speech became coherent he sang the praises of wine as is seen in the 

 numerous references in Egyptian hieroglyphics, Babylonian cuneiform 



