126 DIFFERENTIATION AND SPECIFICITY OF STARCHES. 



(16) This body is doubtless the same as that prepared in an impure state by Herzfeld, 



and described by him as maltodextrin. 



(17) Maltodextrin, they hold, is not a mixture of maltose and dextrin, as is proved by a 



number of facts. 



(18) While maltodextrin is unfermentablc by yeast it is converted into fermentable, 



crystallizable maltose by malt extract and by certain forms of Saccharomyces. 



(19) They believe that maltodextrin is not a mere hydration product of achroodextrin, 



but that it is produced from starch and the polymeric dextrins by the fixation of a 

 molecule of water upon the ternary group (Ci2H2oOio)3 (of which there can not be less 

 than 5 in the starch molecule) which results in the separation from the dextrin resi- 



due maltodextrin < (c^-^^^o^^i This by fixation of two more molecules of water gives 



rise to a freely fermentable, crystallizable maltose. 



In 1889, Brown and Morris (Jour. Chem. Soc. Trans., 1889, lv, 449 and 462) reported 

 the results of further investigations of the constitution of the starch-molecule, and also 

 of the products of transformation. While adhering to their theory of the peculiarities of 

 the groups of the molecule, they believe that the number of groups is distinctly larger than 

 suggested in their previous work. In the first of these articles they study the amylodextrin 

 of W. Nageli in relation to soluble starch, and the relation of amylodextrin to maltodextrin 

 (see pages 115 and 116). 



In the second article they report their determinations of the molecular weights of 

 carbohydi'ates, and state that the following hypothesis seems to them to be in accord with 

 the facts : The starch-molecule may be pictiu-ed as consisting of 4 complex amylin groups 

 arranged around a fifth similar group which constitutes a molecular nucleus. The first 

 action of hydrolysis by diastase is to break up tliis complex and to liberate all 5 amylin 

 groups ; 4 of these groups when liberated are capable, by successive hydrolyzations through 

 maltodextrins, of being rapidly converted into maltose, while the central amylin nucleus, 

 by closing up the molecule, withstands the influence of hydrolyzing agents and constitutes 

 the stable dextrin of the low equation, which, as is known, is so slowly acted upon by 

 subsequent treatment with diastase. The 4 readily hydrolyzable amylin groups are looked 

 upon as of equal value and in their original state to constitute the so-called high dextrins, 

 which can never be separated completely from the low dextrin by any ordinary means of 

 fractionation. This hypothesis provides for intermediate maltodextrins and amylodextrins 

 whose number is only limited by the size of the original amylin group. Each amylin group 

 of the 5 has the formula of (C12H20O 10)20 ^^^^^ ^ molecular weight of 6,480, so that the entii-e 

 starch-molecule, or, more correctly speaking, that of soluble starch, is represented by 

 5(Ci2H2oC)io)20) having a molecular weight of 32,400. They state that the dextrins are 

 metameric and not polymeric compounds, as had already been suggested by O'SuUivan. 



A special study of dextrins, and with reference to the dextrin products of both enzymic 

 and acid action, was made by Effront (Moniteur Scientifique, 1889, 513). He notes that 

 dextrin can be obtained pure by destroying the sugar present by lactic acid fermentation ; 

 and for the purpose of the determination of the sugar and dextrin he would destroy the 

 sugars by ammonium hydroxide and sodium hypochlorite, and determine the dextrin by 

 the polariscopic readings before and after the sugar destruction. (See also page 150.) 



Improved processes for preparing dextrin were devised by Schumann (Jour. Soc. 

 Chem. Industry, 1888, vii, 335; 1889, viii, 295). By the first process 1 per cent of fixed 

 acid is agitated and allowed to stand for 24 hours with cold starch in milky form. The 

 water is then separated from the precipitated starch, and the latter is washed with fresh 

 water until free of acid. The washed starch is once more reduced by water to a milky 

 state at 15 Baume, and then boUed under pressure of 3 to 4 atmospheres with 0.5 per cent 

 of saturated sulphurous acid solution until the fu-st trace of glucose can be detected in the 

 product. The reaction is then stopped, the shght trace of sulphuric acid formed is fixed, 

 and the syrup is filtered through animal charcoal and evaporated. In the second process 



