SCALDING, PRECOOKING, AND CHILLING 35 
organism which survived 4 hours at 100° C, and mentioned others 
that withstood this temperature for 8 hours and 16 hours, respec- 
tively. Burke (#0), in researches on the resistance of the spores of 
Bacillus botulinus, the organism responsible for much sickness and 
many deaths through eating food poisoned by it, reported that the 
temperature of 100° C. inhibited the development of the spores, so 
that the incubation period greatly lengthened, but found that 4 
hours of boiling was not sufficient to kill the spores from hardy 
strains of this organism. Bigelow and Esty (8) , in studies on a con- 
siderable number of thermophilic bacteria isolated from spoiled 
canned food, found that some of these were still alive and able to 
develop after exposure, in corn juice, to the temperature of 100° C. 
for 19 to 20 hours. Their resistance to temperature was found to vary 
when heated in the juices of other vegetables, but in none were they 
completely destroyed in the time required for efficient preliminary 
scalding of the vegetables. No retardation in germination of spores 
of these thermophiles as a result of exposure to high temperature 
was observed. 
These findings of different investigators show conclusively that 
the treatment which the spores of bacteria receive during preliminary 
scalding can not be relied upon to destroy them or materially weaken 
their vitality. 
Within recent years, the notion became prevalent that sudden 
change from high to low temperature decreased the resistance of 
bacterial spores to subsequent heating, and out of this belief was 
developed the practice in home canning of plunging freshly scalded 
vegetables into cold water just before putting into the cans. The 
assertion of the germicidal effect of sudden changes of temperature, 
however, led to careful studies by different workers in various parts 
of the country, and the findings of some of these are presented here- 
with, as they have a direct bearing on the subject in hand. 
Avers and Johnson (^), working in the Government laboratories 
in 1913, reported the results of studies on the bacteria which sur- 
vived pasteurization of milk. These investigators found that milk 
pasteurized at 62.8° C. (145° F.) for 30 minutes, and then cooled in 
15 seconds to 1.7° to 3.9° C. (35° to 39° F.), showed as many viable 
bacteria after the chilling as in milk pasteurized for 30 minutes 
at 71.1° C. (160° F.) and then chilled as before; and, from these 
experiments, they concluded that sudden cooling was of no value in 
causing destruction of bacteria, at least within the range of tem- 
peratures then used. Bushnell (21), in a long series of experiments 
on the sterilization of canned foods, showed that the thermal death 
point of pure cultures of bacteria was not affected by the treatment ; 
that the length of the scalding period (5 to 20 minutes) , or the rapid- 
ity of cooling, did not in any way influence the ease with which the 
spores were subsequently killed by heat ; that spores of bacteria 
were not devitalized by chilling; and that scalding for rather long 
periods followed by plunging into cold water did not aid in steriliza- 
tion of canned foods. 
Buchanan and his collaborators (19) — in a preliminary report 
of experiments with the Bacillus pseudotetani in spore form, to de- 
termine the effect of scalding and chilling by calculating the velocity 
coefficient of the death rate of bacteria that had been heated and 
chilled with a similar coefficient of unchilled bacteria at temperatures 
