34 



BULLETIN 1022, IT. S. DEPAKTMEjSTT OF AGBICTJLTUKE. 



These figures seem to indicate that sealing at initial temperatures 

 as high .as 85° C, or even higher, may be practiced without great 

 danger of serious denting or collapsing of No. 2 tin cans. 



Various influences tend to affect the results in individual cans — 

 the weight of the tin plate from which they are made, the perfection 

 in form, etc. The data shown in Table 10 represent an average for 

 one lot of cans and are given for what they are worth. 



HEAT PENETRATION. 



The time-temperature relation for a No. 2 can of corn started at 

 various initial temperatures, processed for various lengths of time 

 under different retort conditions, and cooled in air and in water are 

 given below. 



*■ 







,x 



































110° 













y\ \ 



: 



r ff\p 





































uj 100 



2 so 



° 70 



| 60 



< 



4tf 

 3rf 

 20° 

















































































- 









™t 



fad 

 /A 











































































































































































































































> 1 



> 



2 



) 3 



) 4 



3 5 



) e 



7 



& 



3 9 



3 IC 



o 1 



O 



12 



a 



i; 



w 



O is 



\i 







1* 







IE 









2d 



Fig. 21. — Experimental time-temperature curves for " Maine style " corn in No. 2 tin 

 cans, starting at different uniform temperatures and processed at 116° C. Proportion 

 of corn to liquor,, 4 : 1. Curves are also given for cooling in air at 26° C. and for 

 cooling in water at 20° C, one curve of which is for corn of heavier consistency. 

 Curves for can starting: A, At 26° C. ; B, at 401° C. ; C, at 50° C. ; D, at 61° C. ; 

 E, at 70° C. ; F, at 80° C. ; (?, at 90|° C. ; H, at 100° C. ; X, at 116° C. and cooled in 

 air at 26° C. ; Y, at 116° C. and cooled in water at 20° C. ; Z, at 116° C. and cooled 

 in water at 20° C, the consistency of the corn being heavier than that represented 

 in curve Y. 



Figure 21 gives the experimental he.at-penetration curves for No. 

 2 cans of corn starting at various temperatures and processed at 

 116° C. 



These show how differences in initial temperatures modify the 

 form of the time-temperature curve. Theoretically, the temperature 

 at the center of the can should reach the temperature of the retort in 

 the same time for any initial temperature, but in these tests the cans 

 starting at the higher initial temperature actually reached the tem- 

 perature of the retort in a slightly shorter time. This would seem to 

 be due to some convection occurring in corn of this consistency. 



Thompson (9) has given a formula by means of which from a 

 single experimentally determined heat-penetration curve one may 



