DEXTRINS 125 



two hours, while the second one is very slow. According 

 to Maquenne and Roux, the first stage corresponds to the 

 hydrolysis of the amylo-cellulose (amylose) and the solution 

 of the amylo-pectin with consequent formation of dextrins ; 

 the second or slow stage consists in the hydrolysis of these 

 dextrins into maltose, and they consequently regard amylo- 

 pectin as a maltosane. 



It was mentioned above that a larger yield of non-maltose 

 is obtained at higher temperatures, and that this is regarded as 

 a mixture of dextrins, since some of it is readily converted into 

 sugar on adding more diastase, whilst some still remains which 

 resists; this latter is most likely produced from the amylo- 

 pectin and corresponds to the stable dextrin described by 

 Brown and Morris, whereas the easily converted portion is 

 in all probability identical with what Brown and Morris called 

 maltodextrin or amyloin, and may have been produced by 

 a peculiar action of malt on the amylo-cellulose (amylose) 

 constituent of the starch. 



General Properties of Dextrins. 



From what has been said above, it will be seen that the 

 term dextrin comprises a number of substances some of which 

 are not at all well defined. The following may, however, be 

 regarded as approximately representing the characteristics of 

 all substances included in this group : 



1. They are amorphous substances which are readily soluble 

 in water to form gummy solutions, which are used as a sub- 

 stitute for natural gum ; they are precipitated from aqueous 

 solutions by the addition of alcohol. 



2. Unlike starch inulin and glycogen, dextrin does not 

 give a precipitate with basic lead acetate. 



3. As their name implies, they are strongly dextro-rotatory, 

 in which respect they resemble starch. 



4. They give either a red colour or no colour at all with 

 iodine. 



5. They are not fermentable by yeast alone, but are fer- 

 mented by a mixture of yeast Ind diastase acting together, 

 which is no doubt due to their slow hydrolysis in the first 

 place by the diastase and the subsequent fermentation of the 

 maltose so produced. 



