116 



U. S. BUItEAU OF FISHERIES 



one that permits ready circulation of hot air and gases amono- the 

 mass of Avhole heads and whole peeled shrimp waste. The direct 

 externally heated rotary drier should be aA^oided because the stoppage 

 of the drier would permit burning Avhich would make the product 

 unsalable. The shelf type or tunnel drier, as shown in Figure 2, 

 would require the least power equipment and would give a satisfac- 

 torily dried product. In all cases such driers should be on hand to 

 reduce the sun-dried stock to 5 per cent moisture content. The drier 

 built of sheet steel with removable shelves of steel plates is inexpen- 

 sive and quite flexible and is able to handle either a large or small 

 amount of stock. Sliding trays can be arranged so as to provide a 

 zigzag course for the heat to pass under and over the trays. The 

 drying process is conducted by removing the lower dry tray, and 

 moving clown each upper tray, and supplying a fresh tray in the 

 upper slide. The rate of drying in such a drier depends upon the 



Figure 



-Trays used for platform drying 



amount of heat supi)lied and the loss of heat in the walls. Under no 

 circumstance should the cost of drying be over one-third cent per 

 jxnind to obtain a product with 5 per cent moisture. 



Grin ding. — The nature of the di'ied product requires the use </f 

 feed i)Y grain grinders for reducing to desirable size. The spiny 

 parts of the shrimp heads and tails are very brittle when dried and 

 grind easily, as do the legs and body shell. The meaty portions in 

 the heads and waste shrimp must be dried before grinding and giA <■ 

 trouble unless the grinding is done step wise, first reducing the stock 

 to about 9 mesh to the square inch size, then to about 25 mesh, and 

 finally to the desired or fine size. The demands for the product will 

 control the size of the ground stock, but, in order to reduce the spines 

 to a harmless size, the grinding must be carried down to about 16 

 mesh, or lower, per square inch. A grinder of this type is the ordi- 

 nary grain or feed grinder, with revolving disk plates to disintegrate 

 tlie particles. These may be j^urchased in any size, but one of 5 



