On the Diastase o/Koji. 



327 



rotatory power remains practically stationary at 164—168° for 1 j hour, 

 then, when a fresh addition of the hoji extract was made, the curve 

 rapidly falls to 131°"8, at which point it again remains fixed, if we 

 assume, as is probable, that the result at three hours is erroneous. 

 The first stoppage, and doubtless also the second, was caused by the 

 exhaustion of the activity of the hoji, and not to the decomposition of 

 the starch at that point according to any definite chemical equation, 

 because the action goes on immediately after the addition of a fresh 

 quantity of diastase, and ceases after about the same time. 



At 60° C, therefore, the activity of the diastase is very quickly 

 destroyed, and at 70° C. the action is so small that no satisfactory 

 determinations could be made. The extract of 10 grms. of hoji, pre- 

 viously heated to 70° C, was added to starch-paste containing 2 grms. 

 of dry starch. After fifteen minutes the solution diluted to 250 cub. 

 centims. only contained 0'40 grm. of solid matter, and caused a 

 scarcely perceptible rotation of the ray of polarised light. We may, 

 therefore, conclude that at some point between 60° and 70° C, the 

 diastase of hoji is destroyed. 



The experiments described do not allow us to conclude that the 

 starch molecule breaks up in a definite manner under the influence of 

 hoji diastase, as appears to be the case with the starch molecule under 

 the influence of malt diastase (O' Sullivan, Brown and Heron, 

 &c), but they do not contradict the supposition, and the results are 

 just such as might be expected, knowing the comparatively energetic 

 action which the hoji solution has upon dextrin, and especially upon 

 maltose. 



The diastase of hoji resembles that of malt in one respect, that its 

 activity is lessened by the presence of certain bodies, such as common 

 salt. In preparation for an investigation into the chemistry of the 

 " Soy " manufacture, Mr. Watanabe made some experiments upon the 

 influence of varying amounts of common salt upon the activity of the 

 hoji solution. In each experiment 5 grms. of dry starch were gela- 

 tinised, and when cold the given amount of common salt was added. 

 The whole occupied about ] 50 cub. centims. The required amount of 

 hoji extract was then added and the mixture left for one hour. At 

 the end of that time the solution was diluted to 250 cub. centims. and 

 filtered. The results give the cupric oxide reducing power of the 

 solid matter in solution, and the specific rotatory power, both 

 corrected for the salt and hoji extract previously added. 



vol. xxxn 



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