32 



BULLETIN 1022, TJ. S. DEPARTMENT OF AGRICULTURE. 



to give the proportion of corn to liquor of 4 to 1. The corn was then 

 precooked over steam with constant stirring until the temperature 



reached 80° C. It 

 was then weighed into 

 the ISTo. 2 test cans, 

 550 grams being used 

 in each case, brought 

 to the desired uni- 

 form temperatures, 

 sealed, the tests im- 

 mediately begun, and 

 the time -pressure 

 curves determined. 

 This procedure held 

 for those cans sealed 

 at 70° and 80° C. 

 The procedure -was 

 the same with the 

 cans sealed at 20° to 

 24^° C, except that 

 in one set of experi- 

 ments the corn was 

 precooked to 100° and 

 in the other the corn 

 was placed in the test 

 cans without any pre- 

 cooking at all. Proc- 

 essing in all cases was 

 for 120 minutes or 

 thereabouts at the re- 

 tort temperatures of 

 100°, 116°, and 121° 

 C, respectively. Fig- 

 ure 20 shows the 

 curves obtained in 

 these tests. 



These curves dem- 

 onstrate the following 

 facts : 



Fig. 20. — Experimental time-pressure curves for corn in 

 No. 2 tin cans, sealed at different uniform temperatures 

 and 'processed for 2 hours at 100°, 116°, and 121° C. 

 Prepared " Maine style " ; 550 grams of material used. 

 Proportion of corn to liquor, 4 : 1. Curve for corn : A, 

 Precooked at 100° C, sealed at 24J° C, and processed at 

 100° C. ; a, precooked to 100° C, sealed at 24£° C, and 

 processed at 116° C. ; a', precooked to 100° C, sealed at 

 24J° C, and processed at 121° C ; B, precooked to 80° 

 C, sealed at 70° C, and processed at 100° C ; %, pre- 

 cooked to 80° C, sealed at 70° C, and processed at 

 116° C ; b', precooked to 80° C, sealed at 70° C, and 

 processed at 121° C ; C, precooked to S0° C, sealed at 

 80° C. r and processed at 100° C. ; c, precooked to 80° 

 C, sealed at 80° C, and processed at 116° C ; & ', pre- 

 cooked to 80° C.j sealed at 80° C, and processed at 121° 

 C. ; X, with no precooking, sealed at 20° C, and proc- 

 essed at 100° C. ; x, with no precooking, sealed at 24 J ° 

 C, and processed at 116° C. ; x', with no precooking, 

 sealed at 241° C, and processed at 121° C. 



(1) The pressure rises 

 almost immediately to 

 a high point when the 

 steam is turned on. as a 

 result of the sudden ex- 

 pansion of the air of the head space. After the first minute the rise is more grad- 

 ual, the rate corresponding largely to the rate of temperature change in the corn. 

 (2) Relatively low pressures are obtained when the higher sealing temper- 

 atures are employed. 



