36 BULLETIN 1265, U. S. DEPARTMENT OF AGRICULTURE 
of 80°, 90°, and 100° C. — could find no significant differences. In a 
further report on these same studies, Bruett (18) expressed the con- 
clusion that bacterial spores, apparently, are not made sensitive to 
heat by a preliminary heating that is followed by chilling ; and that 
the sudden cooling does not cause the bacteria to succumb more 
readily to the sterilization process. 
The writers, during the several years these studies have been 
carried on, have observed as much spoilage in cans that were given 
the combined preliminary heating and chilling as in those where 
there had been scalding only. In the face of the evidence, therefore, 
they come to the conclusion that chilling in cold water immediately 
after scalding serves no useful purpose from the standpoint of ease 
in sterilizing canned foods. 
There remains to be considered in this connection the relation of 
scalding or precooking to heat penetration. Two phases of this 
matter present themselves: The relation of scalding to the rate of 
convection which takes place in the liquid of the can, and the 
relation of scalding or precooking to initial temperatures. 
In a previously mentioned bulletin (37) the writers showed that 
any influence which affects the fineness of division and compactness 
of the material, and the amount and viscosity of the free liquid, 
affects the rate of temperature change in the material in the can. In 
some cases scalding does not bring about material alterations in the 
rate of the convection currents in the can, and in such cases is not im- 
portant ; but in some instances scalding increases the viscosity of the 
liquid and, because of the slowing down of the convection currents, 
delays complete sterilization. In another bulletin, also previously 
mentioned, the writers (38) showed how differences in initial tem- 
peratures affect the time-temperature curves during canning opera- 
tions, higher initial temperatures allowing of possible shortening 
of processing periods, and lower initial temperatures making more 
processing necessary to get the same degree of temperature at the 
center of the can. Scalding, w r hen followed immediately by process- 
ing, therefore, may shorten the processing period; and chilling, 
when this is practiced, makes more prolonged processing necessary. 
The practical application of these facts should be clear to all. 
ECONOMIC CONSIDERATIONS. 
The modern housewife demands canning methods that are simple 
and time saving. Unnecessary steps must be eliminated. In the case 
of the commercial plant, success or failure of the enterprise depends 
on the time and labor necessary for the production of the finished 
product. Scalding, precooking, and chilling are costly operations — 
costly in time, labor, fuel, and, sometimes, food material. Careful 
thought, therefore, must be given to this matter, and practices must 
be justified by considerations of economy before they are adopted. 
Experimental work has shown that with several vegetables — such 
as peas, Lima beans, and string beans, especially when packed in 
glass — the differences in quality between the scalded and unscalded 
products were too small to be significant. In other cases, as with 
spinach canned in tin, the quality was favorably affected by scalding. 
The main advantages of scalding, in most cases, seemed to be the 
