26o 



SCIENCE- 



[VoL. XIX. No. 483 



six thousand by the end of twenty-four hours, and usually they will 

 produce a much larger number than that. So that bacteria are 

 growing in this ripening cream with absolutely incredible rapidity. 

 Now, you butter-makers know that you gain some advantage 

 from ripening the cream, or, at least, you think you do. You 

 think your butter churns a little easier and that you get a little 

 moi-e butter from a given quantity of cream if you ripen it, and, 

 above all (and this, perhaps, may be regarded as the chief value 

 of ripening), the butter acquires that peculiar, delicate, pleasant 

 aroma which is essential to a first-class quality of butter, that 

 peculiar aroma which is not acquired if you do not properly ripen 

 your cream before churning it. 



Now, the explanation of the production of that aroma is simply 

 this: These bacteria ate agents of decomposition. Bacteria, as 

 they grow in any solution, tend to decompose it or pull it to pieces. 

 If they grow in an egg, they decompose the egg and cause it to 

 putrefy and decay, and when they begin to grow in your cream 

 they begin the same process of decomposition. If you should let 

 your cream ripen for a week or two, you would very readily see 

 that the process of decomposition had taken place, and your cream 

 ■would become very offensive. The moment you begin to ripen 

 your cream, the bacteria begin to decompose it. Now, as the re- 

 sult of decomposition,. a great many chemical products are pro- 

 duced, and they have all sorts of smells and tastes. It you should 

 let decomposition go far enough, you would get the bad odor of 

 decay, but you do not get that odor when decomposition begins. 

 The first of the decomposition products are rather pleasant in odor, 

 and pleasant in taste, and if you churn your cream at that stage 

 of decomposition, your butter is flavored with the early decom- 

 position products. This flavor is the aroma of good butter, this is 

 what fancy butter-makers sell in the market and get a high price 

 for. They get a high price, then, for the decomposition products 

 of bacteria, for a proper tasting butter brings a higher price than 

 that which does not have this aronia, and tbe aroma is the gift of 

 bacteria. You may ask, What becomes of the bacteria ? Itreally 

 makes little difference what becomes of them. Some go into the 

 buttermilk, some go off in water used in washing, some go into 

 the butter and the salt kills them. It is no matter where they go. 

 After the butter is churned they are no longer of any importance 

 to you or any one else ; their career, so far as the dairy is con- 

 cerned, is ended. 



If the butter-maker owes something to bacteria, the cheese- 

 maker owes everything to them. The butter-maker cannot get 

 the proper aroma without the agency of bacteria, but the cheese- 

 maker cannot get anything. Of course you all know that fresh 

 ■cheese is very inane and tasteless. Nobody likes fresh cheese. 

 It has a sort of curdy taste and is quite unpalatable. You know, 

 however, that after cheese is made, it is set aside for a number of 

 weeks to ripen. It may ripen several weeks, or, perhaps, months. 

 Sometimes in the case of the best cheeses, it may be ripened a year 

 or more. Now, during that ripening process, exactly the same 

 changes are taking place that I have mentioned in cream. The 

 bacteria are growing, are attacking the casein, and pulling it to 

 pieces. They produce many changes in it, and cause an accumu- 

 lation of all sorts of materials which have peculiar tastes, and little 

 by little the cheese is ripened. After a while the cheese begins 

 to have a pleasant taste and then a strong taste, and if you leave 

 it long enough, you get a very strong cheesei The longer you 

 ripen a cheese, the stronger its taste becomes. An old cheese is 

 always a strong cheese, a fresh cheese is always a mild cheese. 

 The shorter the time you cultivate bacteria in it, of course the 

 slighter will be the changes which they produce; the longer you 

 cultivate the bacteria, the stronger becomes the cheese. 



Now, in the ripening of cheese, we find the cheese manufac- 

 turer's greatest difSculty. Every cheese manufacturer knows that, 

 under conditions which seem to be exactly alike, he may get good 

 cheese and he may get bad cheese. His cheese may become tainted, 

 it may become spotted with little red spots or some other abnormal 

 conditions may appear which he cannot account for. It would be 

 the greatest boon possible to the cheese-maker if we could, in 

 some way, enable him to correct his abnormal ripening processes, 

 and be able always positively to insure the proper sort of ripen- 

 ing. Now, this is plainly a matter which is connected with the 



planting of the proper kind of bacteria in a cheese and planting 

 them under proper conditions. Different kinds of cheeses are on 

 our markets. We have the Edam cheese, we have the pineapple 

 cheese, we have the Neufchatel cheese, we have the Limburger 

 cheese, and many other kinds. Of course, we all know that these 

 different cheeses have very different flavors. Now, in the pro- 

 duction of these different kinds of cheeses, there are different 

 methods used. For instance, in the manufacture of Edam cheese, 

 the cheese-maker puts a little slimy milk into the milk that he is 

 going to make into his cheese. That slimy milk contains a cer- 

 tain species of bacteria, and that peculiar species connected with 

 that slimy milk produces the peculiar flavor which we get in the 

 Edam cheese. Sometimes cheese is allowed to ripen soft for a 

 few days before it is pressed, and when thus ripened, different 

 kinds of bacteria grow in it, and grow in it more rapidly and pro- 

 duce different odors. Experiments have just been begun along this 

 direction which show that it is possible artificially to ripen cheese 

 abnormally. You can take certain species of bacteria and grow 

 them in cheese, and you get a very atrociously tasting cheese, and 

 you can take others and get a very good cheese. Now, in the 

 use of yeasts, we have learned to plant yeast in our bread ; we 

 have learned to plant yeasts in our material that we want to fer- 

 ment, if we are going to make alcohol, or, if we are going to 

 make beer. The brewer has learned that he must use an artifi- 

 cially prepared yeast. He has learned that if he simply allows 

 the malt to ferment naturally through the agency of atmosphere 

 yeasts, he does not know what he will get. It will ferment, un- 

 doubtedly, but it will be likely to ferment in an abnormal manner. 

 He, therefore, plants a pure culture of the proper yeasts. But we 

 have not yet learned to plant bacteria in the same way. The 

 cheese-maker has not yet learned to cultivate bacteria as the 

 brewer has learned to cultivate his yeasts. Some day, I think we 

 may say in the not far distant future, after our Experiment Sta- 

 tions have had time to work upon this matter a little longer, the 

 cheese-maker is going to be told of some way in which he can 

 cultivate bacteria as the brewer does his yeast, and then he will 

 know what kinds of bacteria will produce a badly-ripened cheese, 

 and what kinds will produce an exceedingly good cheese. The 

 time is coming, it has not come yet, but when it does come, we 

 can see that there will be a tremendous development of the cheese 

 industry in this country. 



We know there are four or five hundred species of bacteria in 

 the world. They all produce different sorts of decomposition, 

 they all produce different odors and different flavor's, and when 

 our scientific stations have taught our cheese-makers to cultivate 

 their bacteria and plant particular kinds of bacteria in the milk 

 of which they are going to make cheese, perhaps we are going to 

 have four or five hundred different kinds of cheese. For aught 

 we can see, it may be that tbe various species of bacteria will pro- 

 duce different flavored cheeses, and perhaps fifty years from now, 

 perhaps in less time, a man may go to the store and order a partic- 

 ular kind of cheese that was made by a peculiar kind of bacteria, 

 and another one made by another kind. We cannot tell what 

 possible development there may be of the cheese industry in the 

 future, and whereas now the cheese-maker must depend very 

 largely upon accident for the particular kind of flavor he is going 

 to get in his product, then he will be able to tell absolutely what 

 he must use in order to be able to produce the flavor that he wants. 

 The result will be a great development of the cheese industry, if 

 such time ever comes. 



There will be another advantage in this development when it 

 comes. We all know that once in a while cheese becomes poison. 

 Everyone has read in the newspapers accounts of people who 

 have been poisoned by eating cheese. Under certain conditions, 

 cheese is very distinctly poisonous, and has produced very many 

 cases of sickness and many cases of death. Now, our chemists 

 have studied this poisonous cheese. They have found that it is 

 poisonous because of the production of a peculiar chemical sub- 

 stance in it which they have called "tyrotoxicon." They have 

 found, further, that this tyrotoxicon is a poison produced by a 

 certain species of bacteria. Once in a while that poisonous kind 

 of bacteria gets into milk. The cheese manufacturer is entirely 

 innocent ; he cannot help it, because he has no means of knowing 



