1923] 



JENNISON — POTATO BLACKLEG 53 



tion are slightly erroneous, since, as is well known, more or less 

 destruction of hexose sugar takes place in the process of hydro- 

 lyzing carbohydrates by heating in the presence of an acid. It 

 may be recalled, too, that variability in the reducing power of 

 lactose and of maltose is a characteristic of these disaccharides. 

 According to Browne ('12, p. 402), succeeding portions of lac- 

 tose and maltose will vary in reducing power according to the 

 amount of free alkali, time of boiling, etc. "This peculiarity of 

 maltose and lactose" he says, "is explained by a slight hydrolysis 

 of the sugar into monosaccharides of higher reducing power" 

 during the process of heating. Browne believes that a slight in- 

 version of this kind takes place to a greater or less extent with 

 all higher saccharides (including sucrose) upon boiling with Feh- 

 ling's solution. 



These facts may account in part for the inconsistency of find- 

 ings reported in the literature, to show that moist heat of mod- 

 erate degree causes hydrolysis of certain higher disaccharides and 

 other carbohydrates, such as dextrin and starch. 



In carrying out a number of tests preliminary to the major 

 work reported upon in connection with this phase of the in- 

 vestigation, one experiment is worthy of particular considera- 

 tion, — that made to determine the effect of moist heat upon cer- 

 tain carbohydrates. The temperatures used were those encoun- 

 tered in sterilizing solutions in the autoclave and by the discon- 

 tinuous method. Three different carbohydrate-containing solu- 

 tions were made up: (1) distilled water with 0.5 per cent of 

 the carbohydrates to be tested, (2) Dunham's solutions, acidu- 

 lated by the addition of 0.4 per cent N/1 HC1, separate portions 

 of which contained 1 per cent of the carbohydrates, (3) a plain 

 Dunham's solution which contained 1 per cent of the carbohy- 

 drates being tested. Each of these lots was separated in 3 por- 

 tions. The controls were not heated and were titrated imme- 

 diately. The second set was autoclaved at 15 pounds (121.3° C.) 

 for 15 minutes, the total length of time above 100° C. being 45 

 minutes. The third set was exposed in an Arnold steamer for 

 intervals of 20 minutes at about 99.5° C. on 3 consecutive days. 

 The findings appear in table ix, and it will be seen from the tab- 

 ulated data that sterilization of certain saccharide broths was 

 accomplished by either method without significant hydrolysis 

 of the carbohydrates present when no acid (HC1) was added. 

 Certain of the monosaccharides, as well as the disaccharides lac- 



