FISHERY INDUSTRIES OF THE UNITED STATES, 1938 209 
which can be used in meeting specific situations prevailing in the 
industry. 
During 1938 studies have been made on the suitability of small-unit 
rendering equipment for small canneries not producing enough waste 
to warrant installation of standard fish-meal and oil machinery. 
Attention has been given to the response of salmon waste to dry 
rendering and the conditions necessary to retain the natural properties 
of the rendered oil. Studies have been undertaken regarding the 
preparation of dehydrated protein concentrates which would also 
serve as vitamin A and D concentrates. 
In considering conditions where huge quantities of waste are accu- 
mulated during an extremely short operating period and where a re- 
duction plant of large capacity would have to be idle over 10 months 
out of a year, studies have been undertaken regarding methods of 
chemical preservation and chemical treatment for conversion into 
entirely different type products which could be prepared with a mini- 
mum of equipment. However, because of the limited period during 
which salmon waste representative of commercial operations can be 
obtained, the data from these more specialized studies are as yet 
incomplete and no conclusions can be drawn. The last of a series of 
papers covering the general aspects of salmon byproducts has been 
published. This report is entitled, Investigational Report No. 40, 
“Pacific Salmon Oils.” 
The results show that the waste material or cannery trimmings of 
chinook salmon will yield between 30 and 40 gallons of oil per ton; 
Alaska and coho salmon, from 25 to 35 gallons; pink salmon trimmings, 
from 15 to 25 gallons; and chum salmon waste, from 10 to 15 gallons. 
Since between 80 and 90 percent of the total catch of salmon is canned 
and thus most of the waste material consisting of heads, tail portions, 
fins, and visceral organs are accumulated in connection with cannery 
operations, it can be readily seen that there is a large supply of waste 
material in the salmon canning industry from which oil may be manu- 
factured. The survey further shows that about 30 percent of the 
round weight of chinook salmon is waste material, about 33 percent 
of Alaska red, coho, and chum salmon, and about 35 percent of pink 
salmon constitute waste material from which byproducts may be made. 
This report also contains tables showing the chemical and physical 
characteristics and properties of salmon oils such as iodine number, 
refractive index, specific gravity, etc. This information is of value in 
determining commercial uses for which the oils are best suited. 
STUDIES ON THE PEROXIDE TEST AS A MEASURE OF OXIDATIVE 
DETERIORATION OF FISH OIL 
Oxidative deterioration of fatty fish is a gradual process which even- 
tually manifests itself in rancid odors and flavors readily detected by 
organoleptic means. When such a condition has been reached, the 
product is definitely of poorer quality and less desirable as food. In 
investigations on fish spoilage, the preservation of fish by various 
methods, and in commercial handling of fish, it is highly desirable to 
have some measure of the progress of oxidative deterioration prior to 
the development of rancid flavors and odors, since the problem of 
marketing is to get a product into consumption before the odor and 
flavor is definitely affected. 
