20 BULLETIN 1025, U. S. DEPABTMENT OF AGBICULTUBE. 



if necessary, in order to cover the entire inner surface of the bag 

 with an adhering layer of earth, after which water is passed through 

 until the outer surface is washed free of the earth. The filter is then 

 ready for use. It is well to keep the bag practically full to the top, 

 not only in order that the entire filtering surface may be used, but 

 also because of the more rapid filtration per unit area resulting from 

 the greater weight on the surface. While satisfactory clarification 

 is obtained with such an arrangement, its use should be confined to 

 the handling of very small quantities. 



PASTEURIZING BEFORE FILTERING. 



In the earlier experiments with diatomaceous earth, in the seasons 

 of 1918 and 1919, the juices employed were in all cases pasteurized 

 immediately after pressing and were subsequently stored until the 

 settling out of cellular debris and heat-coagulable material had be- 

 come fairly complete before attempts to clarify them were made. 

 The length of the storage period was determined by convenience and 

 the pressure of other work, ranging from four weeks to nine months 

 as extremes. Sedimentation was usually complete at the end of three 

 weeks in the storage room, which was a room in the laboratory build- 

 ing with no means of temperature control other than a steam coil 

 to prevent freezing in severe weather. 



In some cases the juice, after being decanted from the sediment in 

 the containers, was placed in a large vessel, thoroughly mixed with 

 the earth by prolonged stirring, and allowed to remain undisturbed 

 for several hours or overnight. It was then decanted with as little 

 disturbance of the sediment as possible, mixed with a second smaller 

 quantity of earth, and at once filtered. In other cases the juice was 

 mixed with the earth, allowed to stand for 10 to 15 minutes with 

 occasional stirring, and filtered without permitting settling to occur. 

 As this treatment gave as satisfactory results as the other, all the 

 juices dealt with in the later work were filtered as soon as convenient 

 after being mixed with the earth. 



Juices treated in this manner were brilliantly clear and remained 

 transparent after being bottled, pasteurized, and stored for more 

 than 12 months in a laboratory room subject to wide fluctuations of 

 temperature. The characteristic flavors of juices so treated are not 

 injuriously affected. 



FILTRATION OF FRESHLY PRESSED JUICES. 



Success in the treatment of juices which had previously been pas- 

 teurized and stored led to the hope that it might be possible to apply 

 the treatment to freshly expressed juices, thus dispensing with stor- 

 age and making the whole process of preserving fruit juices a con- 

 tinuous one, in which pressing should be followed immediately by 



