222 KEPORT OF COMMISSIONER OF FISH AND FISHERIES. 



Second only to the careful selection of the livers is the observance 

 of perfect cleatiliness in the entire process of rendering the oil. The 

 livers are thoroughly cleansed from blood and other impurities by 

 washing in several waters, and the gall sacs and attached membranes 

 are removed. Throughout the entire process of expressing and refin- 

 ing the oil, all tanks, receptacles, and the like are kept free from 

 putrefying texture. Some oil-renderers chop the livers into small 

 pieces for the purpose of securing a greater quantity of oil, but this is 

 by no means the general practice. 



There are two general methods of cooking the livers, viz, (1) by 

 wood or coal fire under a water bath, and (2) by the use of steam. 

 The first-named is the oldest in use and is also the most economical 

 where the quantity of material to be rendered is small. Two metallic 

 receptacles or pots are provided, one, in which the livers are placed, 

 fitting loosely in the other, with 2 or 3 inches of space between, and 

 the larger one set into a furnace so that a fire may be built beneath. 

 The space between the two receptacles is filled with water during the 

 process of cooking, and this is renewed as required. A fire is built in 

 the furnace and the water brought to a boiling point, thus imparting 

 a moderate heat to the contents of the pan. In order that the cook- 

 ing may be expeditious the pan should be small, holding not over 50 

 or 60 gallons. Furthermore, it should be narrow, for greater ease in 

 stirring and to minimize the oxygenizing of the oil. Owing to the 

 cheapness of this apparatus it is quite popular with those who trj'-out 

 only a small quantity of oil. 



In the second method of cooking, steam-jacket kettles are used, the 

 steam-chest being provided with a self-acting safety valve b}' Avhich 

 the pressure can be controlled and regulated. Within the kettle there 

 is usually a stirring apparatus operated by steam power. By means 

 of this apparatus the cooking may be performed much more expedi- 

 tiously than with the former one, as any desired temperature may be 

 secured and uniformly maintained. 



In order to prevent, so far as practicable, the formation of hj'droxy- 

 lated compounds, the alleged cause of the unpleasant eructations or 

 gastric disturbance from which many persons suffer aftei' taking the 

 oil, there was introduced in Norway in 1892 an apparatus for its ex- 

 traction without permitting oxidation to take place. This apparatus 

 is so contrived that the air can be completely excluded from it during 

 the whole operation, the i^rocess being conducted in a current of car- 

 bonic acid gas from the moment the livers are placed in the apparatus 

 until the oil is sealed up in the market receptacles. 



Whatever process of cooking may be adopted, it is desirable that 

 the oil be forced out of the hepatic cells in a short space of time 

 and by a moderate degree of heat only. Tlie length of time usually 

 allowed for cooking is from 2 to 8^ hours, and at no time should the 

 temperature exceed 200° F. The duration of the cooking process is an 



