DIASTASE. 85 



The principle which, in the preceding operations, converts the starch 

 into sugar, must therefore become developed daring germination. 

 This important point in the art of the distiller has been investigated 

 with great ingenuity by M. Dubrunfaut ;* and MM. Persoz and 

 Payen succeeded in separating the peculiar matter in barley-malt 

 which possesses the property of converting starch into sugar. This 

 matter has been called diastase. 



Diastase exists in the seeds of all the cereals which have germi- 

 nated ; it is met with more especially near the germs, it seems even 

 that the radicles contain none of it. Nor is diastase observed in the 

 shoots or roots of the potato ; it is to be met with only in the tubers, 

 around the eyes or points where the young sprouts are developed, 

 precisely as M. Payen has remarked, in the place where we should 

 conceive its presence to be necessary for effecting the solution of 

 the fecula. It is also found to exist in the bark and beneath the 

 buds of trees, always in contact with starch. f Diastase is gene- 

 rally obtained from malt, and when carefully prepared, its peculiar 

 power is such, that one part by weight is sufficient completely to 

 liquefy two thousand parts of starch. Diastase is solid, white, amor- 

 phous, insoluble in pure alcohol, soluble in water and weak alcohol 

 The solution very readily undergoes change ; it becomes acid, and 

 then no longer exerts any action on fecula. When dried, it keeps 

 much better ; still, at the end of two years, it seems to have lost its 

 distinguishing properties. Diastase has no action on vegetable tinc- 

 tures, on albumen, gluten, cane-sugar, gum-arabic, or the woody 

 fibre. That which more especially characterizes it, is its powerful 

 action on fecula ; it may be advantageously used to separate and 

 purify the preceding substances, when they are- mixed with starch. 

 The presence of diastase in malt explains the phenomenon of the 

 liquefaction of starch effected by the action of a small quantity of 

 that substance. This solution is not effected by gluten, nor by hor- 

 deine, as M. Dubrunfaut had imagined. 



By the action of diastase, or of malted barley, the starch on being 

 liquefied is not entirely converted into sugar ; there are other dis- 

 tinct products to be considered in this change. The sirup ob- 

 tained by concentrating the liquefied starch, contains sugar capable 

 of undergoing the vinous fermentation, and a gummy matter, dextrine. 

 These two substances may be separated by means of dilute alcohol, 

 which dissolves the sugar and leaves the gum untouched. The 

 relative quantities of dextrine and sugar produced by the action of 

 diastase are variable, and depend both on the temperature at which 

 the process is conducted, and on the continuance of the reaction 

 In tlie first period of the process, the dextrine predominates ; but it 

 becomes less and less by degrees, and finally gives place to sugar. 



M. Guerin ascertained a curious fact, which shows how the dias- 

 tase developed in plants may act on their starch : reaction takes 

 place even at ordinary temperatures. In one of M. Guerin's experi- 



* Dubrunfaut, M6moires de la Soci6t6 Royale d' Agriculture, annee 1823, p. ^40. 

 t Payen and Persoz, Annales de Chiinie et de Physique, t. liii. p. Ti ' t. Ivi. p. 337 

 9e sirie. 



8 



