854 Mr. Fownes on the Preparation of Artificial Yeast. 



ciently cooled, the ferment added. The results of the experi- 

 ment were, a quantity of beer, not very strong, it is true, but 

 quite free from any unpleasant taste, and at least a pint of 

 thick barm, which proved perfectly good for making bread. 



It appears to me that this simple plan would enable distant 

 residents in the country, and settlers in the colonies, to enjoy 

 the luxury of good bread when a little malt could be got — 

 a very easy home manufacture from grain of any kind : the 

 hops might probably be omitted when the yeast alone was the 

 object. 



A moderately strong infusion of malt which has not been 

 boiled, suffered to stand in a warm place for some days, 

 speedily becomes sour and turbid, and begins to evolve gas ; 

 this change rapidly progresses, carbonic acid is given out 

 plentifully, and a deposit of thick insoluble whitish matter 

 formed, which readily excites fermentation in a dilute solution 

 of sugar; the supernatant liquid contains alcohol, acetic acid, 

 and, I believe, lactic acid. 



When wort which has been boiled and hopped is set aside 

 to decompose spontaneously, the change it undergoes appears 

 to depend very much upon its strength. When weak, three 

 or four days elapse before anything is noticed ; a scum then 

 collects upon the surface, and a brown flocculent substance is 

 thrown down, which is incapable of exciting fermentation in a 

 solution of sugar, while the liquid gives off a flat, offensive 

 smell. If the infusion experimented on be stronger, then the 

 change is different : the liquid becomes turbid from the sepa- 

 ration of a yellowish adhesive substance, a good deal of gas is 

 very slowly emitted, alcohol is formed, and the deposit at the 

 bottom of the vessel proves a pretty active ferment to sugar. 

 The acidity of the liquid is but trifling, and its smell is some- 

 what disagreeable. These differences in the behaviour of 

 boiled wort may also depend upon the quantity of hops added 

 and the length of time during which the ebullition had been 

 continued. 



The effect produced in a spontaneously fermentable liquid by 

 vegetable acids, or acid salts, such as cream of tartar, is a cu- 

 rious subject of inquiry. From an experiment made upon some 

 wort, it appeared not improbable that the result of such addi- 

 tion showed an interference in the formation of lactic acid. 

 We know that when the juice of grapes, or currants and goose- 

 berries, is exposed to the air, the vinous fermentation is set up 

 apparently at once ; whereas in an unboiled infusion of malt, 

 which is destitute of these substances, lactic acid seems to be 

 first formed, although ultimately the two fermentations go on 

 together. 



