48 



BULLETIN 1022, U. S. DEPARTMENT OF AGRICULTURE. 



SPINACH. 



Owing to the limited quantity of raw material for use, the data 

 upon spinach are incomplete. The figures which were obtained, how- 

 ever, are considered of sufficient value to warrant their use, and they 

 are therefore presented for what they are worth. 



The spinach was gathered fresh from the field, carefully trimmed, 

 washed, and then blanched for two minutes in boiling water. It 

 was then placed in the test cans, brought to the required uniform 



temperature, and the 

 tests begun. 



PRESSURE TESTS. 



Figure 36 shows the 

 curves for pressure 

 tests with spinach in 

 No. 2 cans, conducted 

 as with other food 

 materials already de- 

 scribed. 



The salient features 

 of these curves do 

 not differ from those 

 shown in the tests 

 upon corn. As in 

 corn, there is a very 

 sudden rise in the 

 pressure curves, due 

 to the sudden expan- 

 sion of the air in the 

 head space, after 

 which the increase in 

 pressure is more grad- 

 ual. The continued 

 increase in pressure is due apparently to the liberation of gases. 

 In one case this was found to be still taking place at the end of more 

 than three hours. Only one curve is given for cans sealed at low 

 temperatures and none at all for the processing temperature of 100° C. 

 That great reduction in pressure is obtained, however, by sealing at 

 the higher temperatures is shown. 



VACUUM STUDIES. 



The vacuum tests upon spinach, while incomplete, as in the case 

 of the pressure, bring out the following facts clearly : 



(1) The vacuum obtained by sealing the spinach into the can at the desired 

 temperature and then cooling immediately always gives a higher vacuum read- 



fit IN MINUTES 



Fig. 36. — Experimental time-pressure curves for spinach 

 in No. 2 tin cans, sealed at different uniform tem- 

 peratures and processed for 2 hours at 116° and 

 121° C. Curve for can sealed: A, At 181° C. and 

 processed a.t 116° C. ; B, at 70° C. and processed at 

 116° C. ; 6, at 70° C. and processed at 121° C. ; C, at 

 80° C. and processed at 116° C. ; c, at 80° C. and 

 processed at 121° C. 



