MANUFACTURE OF CASEIN. 7 



the hands, better results can be obtained by the use of a simple shaker 

 screen, similar to those used for screening sand and gravel. A box 

 arrangement that is supplied with ground curd by means of a hopper 

 permits the empty trays to be pushed under the screen. A box of 

 that kind can be quickly made at very little cost and will save time 

 and also spread the curd in a uniform thickness, which affords the 

 best drying conditions. When the curd is not spread uniformly the 

 drying time is increased to the time necessary to dry the thickest 

 parts. As the trays are filled they are stacked upon wooden trucks 

 provided with swivel casters, for convenience in running them in 

 and out of the drier. 



The stacked trays, with the curd uniformly spread on each, are 

 run into the tunnel drier where a current of heated air is passed over 

 them. The time required for proper drying depends on : 



The condition of the curd. 



The uniformity of the spreading on the trays. 



The volume and temperature of the air passing over the curd. 



The volume and speed of the air current blowing over the curd 

 should not be excessive, but sufficient to carry the moisture off readily. 

 When the air current ■"is too swift much of the fine dried casein is 

 blown off the trays. A temperature of 130° F. (54.44° C.) has ap- 

 parently no detrimental effect upon the casein and is sufficiently high 

 for all purposes. Casein dried at that temperature comes from the 

 drier in a fine-grained condition and breaks up very easily, while 

 that dried at a higher temperature has more tendency to adhere in 

 one mass and is harder to grind to the same degree of fineness. High 

 temperature results in casein that is more difficult to dissolve, par- 

 ticularly in the presence of greater quantities of fat. High tem- 

 peratures are also very liable to cause discoloration of the casein, 

 especially when impurities, resulting from either poor raw material 

 or faults in the process of manufacture, are present. A temperature 

 no higher than is necessary and never exceeding 130° F. (54.44° C.) 

 should be used in order to lessen the danger of obtaining a darker 

 colored casein. In order to get a product that will keep well it is 

 important to dry the casein thoroughly before it is removed from the 

 drier. It is an easy matter to ascertain when a properly ground 

 curd is dry, but great care must be exercised in determining when a 

 coarsely ground one is ready to be taken from the drier. Since large 

 particles of curd dry slowly they must be broken or cut in two to 

 find out whether the inside is properly dried. Xo trouble need be 

 experienced in drying the casein completely within 7 hours at a 

 temperature of 130° F. (54.44° C), provided the curd has been prop- 

 erly ground and spread upon the trays in the proper manner. 



