DAIRYING. 133 



This involved, as a preliminary, a study of casein (cheese protein) 

 and the products to which it gives rise, for it was found that some 

 of the organisms lived upon these substances and derived their 

 food from them. The result of this first stage of the research 

 is that the Institute now knows the organisms responsible for 

 the serious fault of discoloration in Stiltons, and the conditions 

 (that is, range of acidity) under which they flourish. The work 

 is now proceeding in order to compare these ranges of acidity 

 with those occurring in the production of good Stiltons, to find 

 out whether it is possible to avoid discoloration by modifying 

 the ranges of acidity. To test for acidity, an electrical apparatus, 

 similar in principle to the one used for soil research work {see 

 page 28) is employed. This is essential for accurate work, for 

 it records the intensity of acidity, which is what we require to 

 know. The method is, of course, much too complicated for use 

 on a commercial scale, but the main thing is to discover the 

 facts, and when that is done they can be put into a form in which 

 the cheese-maker can make use of them, and it will no doubt be 

 possible to suggest to him a method of determining acidity 

 sufficiently accurately for his purpose. 



Pig Feeding Experiments. — Under the head of Milk ProducLs 

 we may refer to some experiments conducted at Reading, which 

 were originally started in order to test the value of whey in pig- 

 feeding, but have developed into investigations of considerable 

 importance in their bearing on pig-feeding generally, particularly 

 in its relation to the subject of vitamins {see also page 107). 

 In 1920 the attention of the Institute was directed to the serious 

 loss to the cheese-making industry by the waste of ^vhey. Whey 

 cannot be run into streams or rivers without causing serious 

 pollution, nor can it be satisfactorily dealt with on the land; 

 as a pig food, however, it presented important possibilities, 

 and it was in order to test these, and to ascertain the relative 

 advantages of fresh and sour whey, that the experiments were 

 commenced. It was necessary, however, to consider the value 

 of whey as a winter food from all points of view, as it appeared 

 possible that the beneficial results obtained from feeding whey 

 were not limited to the value of the nutrients which it contained, 

 but were influenced to some extent by the presence of vitamins. 

 A series of experiments was therefore started in the spring of 1920 

 designed to test these points. In the following account, which 

 gives the results up-to-date, frequent reference is made to vitamin 

 A. It should be explained that this is one of those unknown 

 accessory food substances already referred to, which have never 

 been isolated, but are known to be present in certain foods 



