No. 3 (1921) MANUFACTURE OF FISH OIL AND GUANO 213 



109. Avoidance of taint. — Since fish tissues, especially in tropical 

 climates and under the faulty conditions of capture which 

 generally prevail, taint within a very few hours, and since the oil 

 is derived from such tissues, it is obvious that if the oil is to be 

 free from the putrid odour of taint, not only must the fish itself be 

 free from taint, but the oil must be separated with the greatest 

 possible expedition from the tissues which begin to decompose 

 immediately life is extinct; otherwise not only will the oil be 

 malodorous from the beginning but it will contain agencies which 

 at once proceed to decompose the oil itself. Hence the ancient 

 Indian method — found in primitive practice all over the world at 

 one time or other — of obtaining the oil by allowing the mass of 

 sardine, contained in an old canoe or other receptacle, to putrify 

 till the oil, aided by a little water, came to the surface of the semi- 

 liquid mass, necessarily produced a nauseous oil, horrible in odour 

 and taste and colour. The newer method is that of boiling the fish 

 on receipt, and of skimming and expressing the oil forthwith; but 

 it is obvious that even by this method the fish must not be allowed 

 to taint and the oil must be separated at once ; otherwise the 

 former evil, in less degree, would arise. 



no. The nauseous character and in part, the bad colour, of oil 

 from tainted fish is due to the decomposition of the tissues of the 

 fish and especially of the proteid or nitrogenous matter; the 

 decomposition products of these matters are very malodorous, 

 discoloured, and even poisonous, and these products largely pass 

 out with the oil when it is removed from the mass b}'' boiling and 

 Ijressure. 



Now it is very difficult and costly to remove these objectionable 

 products from the oil ; authorities, indeed, say that it cannot be 

 done on a commercial basis if the oil has been obtained from 

 putrid material. Hence it is of the first importance, if fish oil is to 

 take a good place and obtain a good price, that by all means 

 possible the oil should be obtained from fresh fish in which taint 

 has been prevented or at least inhibited. 



It may be added that, in the matter of the guano also, this is 

 important, for putridity means loss of nitrogen in proportion to the 

 degree of taint, the nitrogen being lost as ammonia or passing 

 away in the putrid fluid which exudes from the fish ; since nitrogen 

 is by far the most valuable constituent of the guano, such loss 

 means loss of value and consequent loss of price. 



