STUDIES ON FRUIT JUICES. 3 



entire space between the press floor and the head of the press is 

 filled. 



Racks of hard maple are best, as this wood is very strong and 

 quite flavorless. Extra heavy racks are required in pressing citrus 

 fruits and pineapples. The press cloths should be of the extra- 

 heavy quality, sold by manufacturers of cider and vinegar makers' 

 supplies. 



The rack-and-cloth method has the merit of affording an excellent 

 opportunity for the drainage of the mass of fruit while under pres- 

 sure. An additional advantage is the ease with which the press, 

 racks, and cloths may be kept clean. After pressing it is usually 

 necessary only to wash off the press bed and racks with a hose. 

 When the pomace has been shaken out, the cloths are cleaned by 

 hosing off and by an occasional washing. Racks and cloths must 

 be kept dry when not in use. When operating continuously, racks 

 and cloths are apt to become heavily charged with yeasts which 

 infect the juices passing through and cause fermentation to occur 

 very rapidly, in extreme cases even while pressing. This may be 

 avoided by systematic daily cleansing of racks, cloths, and press. 



The hydraulic type of press, operated by power, is very satis- 

 factory. A steady but relatively light pressure is especially desirable 

 in pressing the juice from the viscous masses formed by the ground 

 pulp of peaches and of some of the small fruits. 



REMOVAL OF SEDIMENT FROM FRUIT JUICES. 



Newly expressed fruit juices are invariably turbid because of the 

 suspended substances present. A convenient way for removing the 

 greater part of the sediment consists in passing the juice through a 

 milk separator, which causes a large portion of the sediment to adhere 

 closely to the walls of the bowl. By filtering through paper pulp a 

 perfectly clear juice may usually be obtained. Infusorial earth 1 is 

 recommended by filter press manufacturers as an aid in the filtration 

 of liquids which contain slime, and the experiments on fruit juices 

 here considered indicate that this substance may be generally used 

 in their filtration. The addition of 2 per cent or less of infusorial 

 earth to a fruit juice will in many cases produce a perfectly clear fil- 

 trate, as the infusorial earth prevents the stopping up of the pores 

 of the filter by the slimy suspended substances of the juice. 



1 Infusorial earth, also called diatomaceous earth, or kieselguhr, consists of nearly pure silica built up 

 of the skeletons of microscopic sea animals called diatoms. When crushed and bolted it therefore exposes 

 an enormous surface to liquids with which it is mixed. It possesses the property of opening up the slime 

 which collects on the filter cloths, which otherwise would choke and render filtration impossible. Infuso- 

 rialearth possesses this property to an extent not possessed by any other known substance. At the same 

 time it is so inert that neutral or acid substances can be filtered through it practically without contamina- 

 tion. It is extensively mined in the United States and may be had finely bolted, ready for use in filter- 

 ing, in carload lots at less than 2 cents a pound. 



