AN EXPERIMENT IN IMPROVING THE MILK SUPPLY 



OF A CITY MILK PLANT. 



(Special Bulletin No. 112) 



L. H. COOLEDGE AND O. T. GOODWIN 



There has been a strong- rleniand among the milk distributors and 

 dairy manufacturers of the State for a better method of determining the 

 keeping quality of milk, both for city distribution and in the manufac- 

 ture of dairy products. Investigations of this problem carried on in the 

 Bacteriological Section of this Station have resulted in the development 

 of the pH method by Cooledge and Wyant in 1919. This method measures 

 the activity of certain bacterial types, of importance in the souring of 

 milk, rather than attempting to determine tlie number of bacteria present. 

 It is being found of value in the improvement of icity milk supplies. The 

 following contest was conducted to judge its use in actually improving 

 the city milk supply of Eaist Lansing, Michigan. 



Milk contests have been originated in attempts to improve the milk 

 supply of various cities and of city milk plants. These have been based 

 largely upon the results of inspections of dairj' farms and milk scoring, 

 by means of the score card. AVitliout doubt these contests have accom- 

 plished a great deal in the way of educating the daiiy farmer as to 

 proper methods. 



Not being satisfied with the above ba.sis for conducting a milk contest, 

 the authors have selected the pH method, origina*ted by Cooledge and 

 Wyant of this Station (1), as being well suited for judging the condition 

 of milk as it arrives at the plant. The pH method attempts to measure 

 the activity of the important acid-producing bacterial groups in the 

 sample rather than to detennine the number of bacteria present and this, 

 therefore, checks with the actual keeping quality of the milk, a thing 

 which other methods fail to do. 



The simplicity and the low cost, together with the fact that results 

 obtained by this method may be reported to the farmer in temis of hours 

 required for samples to sour, rather than as a term or factor which is 

 meaningless to the uninitiated are other reasons wihy we favor this 

 method. 



EXPERIMENTAL MILK CONTEST. 



The time selected for the contest was spring, when the milk usually 

 arrives at the plant in the poorest condition, due, no doubt, to the fact 

 that the farmers are in the habit of depending too much upon the cold 

 weather of winter to cool the milk. 



To stimulate interest in the contest, ten prizes, consisting of five and 

 ten pound cheeses, were divided into two classes as follows : 



