THE AROMA OF BUTTER. 237 



sample of South American milk a fission fungus named Bacillus 

 No. 41, which is not one of the acid bacteria, but produces in 

 milk and cream a fine aroma, identical with the highly-prized 

 flavour known in North America as "grass flavour" or "June 

 flavour," because it is produced only in the month of June, at a 

 time when the cows are foddered, on tender grass rich with blossom 

 and perfume. Cream inoculated with this bacillus yielded butter 

 endowed with this fine grassy aroma. By means of this process 

 butter can now be produced with a uniform degree of excellence 

 and marketable value. The mode of working with this bacillus 

 is simple. A culture of the organism in milk is procured, the 

 usual volume being about J litre (nearly half a pint), and is poured 

 into about 6 litres (1.32 gall.) of Pasteurised and re-cooled cream. 

 After a lapse of a couple of days the whole is transferred to the 

 bulk of the (fresh) cream, which is left for twenty -four hours and 

 will then be ripe for churning. About 6 litres of this ripe cream 

 are reserved for inoculating the next batch in the same manner 

 as before. It will be noticed that the bulk of the cream is not 

 heated, and consequently the lactic acid bacteria therein will be 

 still living and capable of souring the cream, whilst the Bacillus 

 No. 41 acts concurrently and develops the aroma. The latter 

 organism, however, retains the upper hand, having been initially 

 present in excess. This flavour-developer has now been tested 

 and proved in more than a hundred North American dairies, so 

 that its employment can be recommended. Naturally, fresh cul- 

 tures must be introduced into the dairy at intervals (two to three 

 months), since otherwise the bacterium gradually loses its powers. 

 The discoverer of the organism attributes to it the additional 

 faculty of remedying defective butters, but on this point the data 

 at hand are insufficiently conclusive. It should be mentioned that 

 the microbe appears in the form of non-motile short rods, 0.7 //. 

 broad and i.i p, long, generally united in pairs, but never as chains. 

 The optimum temperature is 23 C. Its acid-producing powers 

 are so slight that the milk is never coagulated. The aroma 

 developed in the milk is initially delicate, but becomes progres- 

 sively stronger, and finally (after a lapse of several weeks) resembles 

 that of fine cheese. As a result of further researches published in 

 1896, CONN (II.) was led to conclude that acidification and the 

 production of aroma are independent phenomena. He considers 

 that aroma is developed by the activity of peptonising bacteria 

 which separate volatile bodies (of agreeable or offensive smell and 

 taste) from the albuminoid constituents of the cream. 



143. Defects in Butter. 



The advantages offered by this artificial method of souring 

 cream are only appreciated at their true value when its application 

 cures certain defects in butter to which we will now refer, and 



