materials in the viscera which were definitely identifiable were collected. 

 As nearly as possible a correct proportion of the individual organs were 

 included in the sample. For example, to each digestive tract, one liver 

 and alternately the eggs and milt were selected. Sampling for each species 

 was continued until 10,000 fish had been butchered provided that many fish 

 were available at the time. 



As the work progressed it was obvious, from preliminary analyses of 

 oil samples, that the head portion of the waste contributed the major 

 portion of the quantity of oil, but the viscera contributed the major 

 portion of the vitamin A concentration. For this reason a series of samples 

 of offal were collected to determine the relative contribution of oil and 

 vitamin A for each of these portions of the offal. It was also of interest 

 to ascertain the effect of the presence or absence of any one or more parts 

 of the offal upon the alkali digestion technique. For these particular 

 experiments, then, the additional materials were sorted from the waste. 

 In several experiments the control, consisting of heads and total viscera, 

 was compared to : (l) livers alone, (2) entire viscera alone, (3) viscera 

 less gonads, (4) viscera less milt. All the offal in these particular tests 

 was segregated from the same lot of fish to approximate uniformity of 

 raw material. 



Equipment Used for Alkali Digestion 



The digester used was a wooden barrel approximately 30 inches in 

 diameter and 42 inches in height. A length of iron pipe, ^-inch in diameter, 

 was bent in a semi-circle to conform to the shape of the bottom of the 

 barrel. This pipe was then placed in the bottom of the barrel and connected, 

 by means of a second vertical pipe and a hose, to a source of high- 

 pressure steam. A portable stirrer unit, powered with one-quarter horse- 

 power 1750 RPM direct-drive motor, and equipped with two 3-inch boat-type 

 propellers mounted on a 5/8-inch shaft 28 inches in length was clamped 

 over the side of the barrel. 



For the separation of the oil from the liquor upon completion of the 

 digestion, a DeLaval oil purifier. Model No. 202, was employed. 



Procedure for Alkali Digestion 



The digestion procedure adopted as standard for the prejiaration of 

 the samples of oil from the cannery offal was as follows: 



(1) The salmon waste to be processed and an equal weight of 

 potatle water was placed in the digestion barrel. 



(2) The stirrer motor was started and the steam turned on. 



(3) A solution made by mixing one-half gallon of water with sodium 

 hjrdroxide flakes equivalent to from 1.5 to 3.0 percent of the 

 weight of the waste was added. 



37 



