26 



BULLETIN 1022, IT. S. DEPARTMENT OF AGRICULTURE. 



20° and processed at 116° and 121° C, respectively, the pronounced 

 and repeated bulging of the cans masks this effect. The decomposi- 

 tion of the material under test, if such is the explanation, is less 



marked than in the string beans, but is 

 nevertheless exhibited. 



The relation of blanching to the devel- 

 opment of pressures is clearly shown by 

 the comparison of the curves for the 

 blanched and the unblanched peas sealed 

 at low temperatures and processed at 116° 

 C. Approximately 11 pounds greater 

 pressure was developed in the can of un- 

 blanched material. 



In the work with peas it has been ob- 

 served that the stage of maturity, the 

 amount of blanching, and the fullness of 

 the can have more or less effect upon the 

 pressure developed. The influence of 

 these factors is not here illustrated with 

 curves, however. 



The maximum pressures attained dur- 

 ing the period of processing used in these 

 tests (60 minutes) were slightly below the 

 theoretical values, but above those for dis- 

 tilled water. 



Fig. 14. — Experimental time- 

 pressure curves for peas in 

 No. 2 tin cans sealed at differ- 

 ent uniform temperatures and 

 processed at 100°, 116°, and 

 121° C. ; 400 grams of peas, 

 170 c. c. of liquor. Curve 

 for can sealed : A, At 20° C. 

 and processed at 100° C. ; a, 

 at 20° C. and processed at 

 116° C. ; a', at 20° C. and 

 processed at 121° C. ; a", at 

 19° C. and processed at 116° 

 C, peas unblanched ; B, at 

 70° C. and processed at 100° 

 C. ; h, at 70° C. and proc- 

 essed at 116° C. ; b', at 70° 

 C. and processed at 121° C. ; 

 C, at 80° C. and processed 

 at 100° C. ; e, at 80° C. and 

 processed at 116° C. ; c', at 80° 

 C. and processed at 121° C. 



VACUUM STUDIES. 



The vacuum readings made on the cans 

 used in the pressure tests gave results en- 

 tirely comparable with those for string 

 beans. The vacuums obtained were some- 

 what below the theoretical values and 

 slightly above those for beans. The effect 

 at the higher temperatures was again ob- 

 served, the reading in the case of the cans 

 processed at 116° and 121° C. being lower 

 by approximately 2 inches than those proc- 

 essed at 100° C. 



Those factors which affect the develop- 

 ment of pressure in peas likewise influence 

 the vacuum. The amount of blanching, 

 the maturity of the peas, the liberation of gases during processing, the 

 bulging of cans, and the individual variations in the resistance of 

 cans to external pressure all affect the vacuum readings. 



