CANNING SARDINES 131 
from the air to the fish. Rapid heat transfer can be induced by 
making the temperature difference between the fish and the air large 
and by using high-velocity air to decrease the thickness of the sta- 
tionary film of air surrounding the fish. Thinning this film not only 
increases heat transfer but facilitates moisture removal. Therefore, 
air having as high a temperature and velocity as practicable should 
be used. Temperatures sufficient to cook the fish can be used, and 
this also aids drying, because cooking liberates water from the cells 
of the fish and makes its removal easy. Due to the excellent drying 
conditions that prevail at the surface of the fish, the tendency is for 
the water to evaporate immediately and leave soluble products 
behind. This should keep the skin tough and dry, so that relatively 
small losses of juice and oil take place. While the fish are being 
cooked it should be possible to smoke them lightly simply by adding 
smoke to the drying air. The smoking effect should be accelerated 
by high air velocities in the same way that heat transfer is accelerated. 
Hot fish must be cooled before they can be packed in the cans. 
It should be possible to do this quickly and effectively by blowing 
cool, outdoor air over them. Such air will take away heat from the 
fish in proportion to its velocity and coolness; therefore, the tempera- 
ture should be as low and the velocity as high as practicable. It will 
now be shown how well this theory works out in practice. 
EXPERIMENTAL PREPARATION OF CALIFORNIA PILCHARDS 
Experiments with the new we as applied to the preparation of 
California pilchards for canning, were conducted throughout the 
1923-24 sardine season, first in a small way in the laboratory and 
later on what may be termed a fairly large scale. Near the end of 
the season’s work, during the period March 10 to 15, 1924, the process 
was demonstrated to those canners who accepted a general invitation 
given for this purpose. <A small amount of additional experimental 
work was done in Monterey in December, 1924.” 
EQUIPMENT AND PROCEDURE 
The first experiments were carried out in the drier that had been 
used in the drying experiments. (Fig. 22, p.120.) In order to get a 
temperature high enough to cook the fish all the air in the drier was 
recirculated continuously. Heat was furnished by steam coils, over 
which the air passed, and by gas flames placed under the pipes leading 
to the tunnel and from it to the recirculating duct. In this way air 
temperatures up to 222° were obtained. 
Cooling the air was accomplished by turning off all heat and sending 
airat room temperature through the drier, none of which was recir- 
culated. Cooling was slow, due to so much heat being retained by 
the drier itself. Later experiments were carried out with the cooker, 
drier, and cooler shown in Figure 23. The products of combustion 
from a gas-fired furnace were drawn by suction from the fan through 
a pipe (A) leading to the air-mixing chamber (6). A slide on top 
of the mixing chamber (C) allowed as much cold air as desired to be 
drawn into the fan and mixed with the hot air. The fan for handling 

47 Detailed data covering the experiments are given in Table 42, p. 204. 
