40 



BULLETIN 956, U. S. DEPARTMENT OE AGRICULTURE. 



it requires about 1 hour and 30 minutes to approach the temperature 

 of the bath. At 109° C. it requires about 1 hour and 20 minutes, 



/so 

 //o 



$so 



\ 



60 



SO. 



D_ l 



y^ __c 



JO -90 <50 60 



Fig. 46. — Time-teniperature relations for tomatoes when processed in No. 3 tin q?- 

 100°, 109°, 116°, and 121° C. These curves were plotted from read'- ^ a ac at 

 intervals of 5 minutes. Rise in temperature when processed : A, A ^00° C. ; B, at 

 109° C. ; C, at 116° C. ; D, at 121° C. 



at 116° about 1 hour and 10 minutes, and at 121° it requires 1 hour 

 to reach the processing temperature in a No. 2 tin can. Similar 



results are noticed in the No. 

 3 tin cans and in the pint and 

 quart glass jars. A shorter 

 time is required to reach the 

 temperature of the retort at 

 121° than at any lower proc- 

 essing temperature. With 

 many vegetables and fruits 

 there is a slowing down in 

 the rate of rise as the tem- 

 perature goes higher, owing 

 to the going into solution of 

 starch, protein, or other ma- 

 terial, which changes the vis- 

 cosity of the material. This 

 change in viscosity interferes 

 with convection, and so the 

 process is slowed down. A 

 change of exactly the oppo- 

 site character is taking place 

 in the tomato. The tomato 

 fruit is very succulent, and 

 its tissues are easily broken 



down at high tempera- 



te *?0 SO 60 70 80 SO 

 T/Af£ //V M/NUTES 



Fig. 47. — Time-temperature relations for to- 

 matoes when processed in pint glass jars 

 at 100°, 109°, 116°, and 121° C. These curves 

 were plotted from readings made at intervals 

 of o minutes. Rise in temperature when 

 processed : A, At 100° C. ; B, at 109° C. ; 

 C, at 116° C. ; D, at 121° C. 



