94 U. §. BUREAU OF FISHERIES 
CHANGES IN OIL USED FOR FRYING SARDINES 
INTRODUCTION 
In the first section of this document a description is given (pp. 73 
to 85) of the method employed in preparing sardines in California 
by the frying-in-oil process. Further information will be found on 
pages 103 and 104. At the time this investigation was started (1920) 
virtually all California sardines were being prepared in this way. 
This procedure also was followed to some extent in Maine. Condi- 
tions have changed little since then. 
Continued use of the oil for frying sardines causes it to gradually 
become dark in color and viscous. Eventually the oil becomes al- 
most black when viewed even through relatively thin layers, and 
when cold almost as viscous as molasses. It also acquires a disagree- 
able odor and flavor, both of which are characteristic. Although 
these changes take place gradually, they become quite pronounced 
within a few days. 
When such oil is used for frying, it has a bad effect on the cooked 
fish. A quantity of this oil necessarily adheres to them and is car- 
ried out of the vat. Part of the oil drains away while the fish cool, 
waiting to be packed, yet some remains and gets into the cans; 
except when the cooking oil has seen little use, this is undesirable. 
It would be too expensive, however, to put a new batch of oil into 
the vat, so frying is continued. Where ordinary precautions are 
observed in handling the oil it is improbable that it ever gets insani- 
tary, but conditions do become undesirable and at times very much so. 
Undoubtedly frying-in-oil difficulties were the most important 
ones of a technological nature met by the California industry. They 
were of considerable industrial significance because of the large 
quantity of oil used for this purpose. In 1920 over 50,000,000 
pounds of sardines were fried in California. 
PREVIOUS WORK BEARING ON THE PROBLEM 
As far as it has been possible to determine, no results of any in- 
vestigation on the frying of sardines has yet been published, other 
than a summary (see footnote, p. 91) of this particular study. 
Weber (footnote, p. 72) mentions corn oil as having been used some 
years ago in Maine for frying sardines. The oil gave off a disagree- 
able odor and foamed badly when used. At that time, however, 
commercial corn oil was not as highly refined as it is to-day. Several 
articles were found giving some data on oils used for frying pur- 
poses. Morgan and Cozens* give a good summary of these articles. 
The literature on vegetable, animal, and fish oils is voluminous. 
It is quite well summarized in many places, however. Lewkowitsch ” 
gives the best summary. A series of articles by Hepburn * furnishes 
a good discussion of the changes that take place in oil. Since, in 
the present report, cognizance must be taken of the natural changes 
that take place in the oils, these are briefly described below: 

24 “ Changes in physical and chemical constants of fats used in frying a standard dough.’”’ By Agnes F. 
Morgan and Ella R. Cozens. Journal of Home Economies, vol. 11, pp. 394-402. Baltimore, 1919. 
25 “Chemical technology and analysis of oils, fats, and waxes.’”’ By J. 1. Lewkowitsch and G. H. War- 
burton. 6th edition. Vol. I. London, 1921. f 
* “4 critical study of the natural changes occurring in fats and oils.” By J. S. Hepburn. Journal, 
Franklin Institute, vol. 168 (1909), pp. 365-384 and 431-456; vol, 169 (1910), pp, 22-54, Philadelphia, 
