No. 3 (1921) MANUFACTURE OF FISH OIL AND GUANO 2l5 



If the remaining mass after skimming, or the whole mass 

 without skimming, is then run into draining vats, i.e., wooden or 

 other vats with perforated false bottoms, covered with gauze or 

 cloth, the oil obtained from the drained-off fluid is very good, of a 

 somewhat darker yellow than the skimmed oil, but not greatly 

 different from it if similarly treated ; the difference is that it is 

 considerably longer in contact with the boiling fish tissues, and 

 since it drains from the bottom of the mass it is more contaminated 

 with albuminous fluids and impurities. 



The remaining mass is then pressed, and since the oil has now 

 been for some time in contact with the hot mass and since there is 

 a good deal of colouring matter in the Madras " sardine," the oil 

 from the presses is usually darker in colour than skimmed or 

 drained oil and, by reason of the strong pressure, a large quantity 

 of " impurities," i.e., fluids and matter which are not oil and are 

 usually readily decomposable, is found in the mixed oil and water 

 which flows into the pits. At Tanur pressed oil is usually not 

 deeper in colour than orange, so that the drained and pressed oils 

 are generally treated together, and not being often large in quantity, 

 they are rapidly separated and washed. But if the impure oil and 

 water are left together for some time, e.g., over-night, the oil will 

 be much darker with at least a tendency to off"ensive odour from 

 the decomposition products of the impurities; this, in small tropic- 

 al factories, with a small staff and no very effective means of 

 separating the oil, is a serious cause of inferior, highly odorous, 

 dark oils. 



113. Hence it is important to use means to separate the oil from 

 the fish mass with the greatest possible rapidity ; this is one main 

 reason for the general use in the United States of America of 

 continous operations in which the fish pass in a regulated stream 

 through a steam cooker in the form of a lengthy cylinder traversed 

 by an archimedean screw or conveyor, in which they are kept 

 under the continuous action of steam ; from this cooker the cooked 

 mass is taken by a conveyor and dropped into a continuous press 

 in the form of a conoid or tapering cylinder also traversed by a 

 screw which forces the mass into a gradually contracting space 

 and thus squeezes out the oil and water: the operation takes, for 

 each fish, not many minutes from the entrance hopper of the cooker 

 to exit as " scrap " from the press. 



On the West Coast the manufacturers in general, under a 

 mistaken idea of economy, cram large boiling pans with much fish 



