CONCORD GRAPE JUICE. 



From the heating kettles the fruit is dropped to the press room, 

 where it is made up into cheeses and pressed. 



PRESSING THE HEATED FRUIT. 



The hot pulp is enveloped in strong, coarse-meshed cloths to 

 form layers which are stacked on top of one another. These stacks 

 or "cheeses," as they are called, are then subjected to pressure. 

 The height of the stacks varies in different factories. It may be 

 said, however, that low cheeses are to be preferred to high ones, 

 because they allow a better yield of juice on account of the greater 

 elasticity of the higher cheeses. 



The presses used in the factories are of two types, the hydraulic or 

 power press and the screw or wine press. The number of layers 

 varies with the size and power of the press, and the size of the layers 

 themselves. As a rule, 10 layers (48 by 48 inches) constitute a cheese. 

 While the cheese is being prepared and the number of layers increases, 

 the pressure on the cheese grows, thereby increasing the flow of juice. 

 This flow of juice is called the free-run juice, since it is the juice 

 which is recovered by the weight of the cheese itself without addi- 

 tional pressure. This juice is lighter in color than the juice obtained 

 after pressure is administered, and is practically the juice from the 

 pulp proper. It is materially lower in acid and has less tannin and 

 body than the final juice after the pressing process is completed. 

 The free run amounts to about 56 per cent of the entire quantity of 

 available juice in the fruit. Before the pressure is applied the cheese 

 should be allowed to settle. This settling period is of importance, 

 as it allows the coarse particles of pulp gradually to shift with the 

 flow of juice to the sides of the cloths, followed up by finer material; 

 thus a very efficient filter for the juice is provided. If the pressure 

 were applied without allowing the cheese to settle, the advantage 

 due to the collection of this filtering material and its consequent 

 clarifying effect would be sacrificed. Although obviously advanta- 

 geous to allow the cheese to settle before applying pressure, it is not 

 absolutely necessary. It is evident, however, that the greater the 

 amount of suspended matter removed from the juice before it is 

 bottled for storage the better will be the precipitation so far as com- 

 pactness is concerned, an advantage not to be underestimated be- 

 cause of the better conditions for siphoning. Although the time 

 allowed for the settling of the cheese varies in the different factories, 

 15 minutes is quite sufficient for this operation. This is shown in 

 figure 1. The first 10 minutes served to build the cheeses. The 

 time of settling was varied to show the effect of time upon the re- 

 covery of free-run juice. Table 5 gives the data shown in figure 1. 

 39092°— 18— Bull. 656 2 



