CHEMICAL TESTS AND ANALYSES 259 



two and one-half inches above the bottom. Every day at a regular 

 hour the samples of the ages above stated are placed into this tray, 

 containing water at the desired temperature (60 to 70 degrees F.), 

 about thirty minutes before the cans are opened. All cans should 

 be placed in the tray right-side up. 



Upon opening the cans, the coating on the lid shows the pres- 

 ence of sugar sediment and of lumps of curd in the case of sweet- 

 ened condensed milk, and a layer of thick and buttery cream in the 

 case of evaporated milk. A perfectly clear lid, without any coating, 

 indicates the freedom of the product from these defects. In the 

 case of fermented milk the ends of the cans are usually bulged. 

 Upon opening, a part of the contents is forced out. The thickness 

 is estimated by inserting a spatula, or spoon, or by pouring, and the 

 flavor and smoothness are determined by tasting. 



The observations should be carefully recorded in a book re- 

 served for this purpose, and any changes observed as the milk ad- 

 vances in age should be noted. 



Interpretation of Results. Most of the physical and mechan- 

 ical defects appear in milk from one to ten days old. Defects re- 

 sulting from fermentation processes generally become noticeable 

 two to three weeks after manufacture. 



Fluctuations in the thickness, from batch to batch, indicate lack 

 of proper attention on the part of the pan-man to the "striking" of 

 the batches. Sugar sediment shows the need of closer attention to 

 the solution of sucrose and the cooling of the condensed milk. 

 Lumps and buttons suggest the acceptance of a poor quality of 

 fresh milk, or unsanitary condition of milk cans, vats, pipes and 

 conveyors in the factory, or unclean tin cans. Fat separation and 

 curdiness of evaporated milk suggest a faulty process. Fermenta- 

 tion of sweetened condensed milk urges investigation of the quality 

 and condition of the sugar and of the sanitary condition of all ap- 

 paratus and conveyors of milk, condensed milk and sugar, from the 

 forewarmers to the sealing machine. Fermented evaporated milk 

 points to incomplete sterilization or leaky tin cans, etc. 



Systematic Examination a Necessary Feature of Economic 

 Manufacture. Manufacturers who neglect to conduct a systematic 

 examination of their product similar to that outlined above fre- 



