150 DIFFERENTIATION AND SPECIFICITY OF STARCHES. 



ences in the products, but also more or less marked differences in the stages, at least in 

 certain cases. In fact, not only are dissimilarities to be observed between the effects of 

 enzymes and acids, but also between the effects of different enzymes and different acids. 



Different enzymes might be expected to yield somewhat different results, owing in 

 part to differences in origin in plant and animal Hfe respectively, but chiefly because 

 enzymes, as ordinarily used or prepared, are seldom individuals, but composites of several 

 distinct enzymes, varying in regard to kind and quantity and in their specific actions. 

 If the progress of the action of anirtuil enzymes (ptyalin and amylopsin) on starch be traced 

 by testing from time to time with a very dilute iodine solution (1 per cent Lugol's solution), 

 the blue reaction noted at the very beginning of digestion gives way to a purple, and tlais 

 to a violet, this color persisting but becoming weaker and weaker, up to the time of the 

 final disappearance of all color response with the iodine. With plant enzymes and v/ith 

 add the blue reaction gives way quickly to a red or brovmish-red reaction which may ulti- 

 mately pass into a reddish yellow, gradually fading away. This certainly indicates some 

 differences in the intermediate products. Moreover, whether there is produced by enzymic 

 action only maltose, or both maltose and isomaltose, or maltose and isomaltose and dex- 

 trose, etc., will be found to depend solely or almost entirely upon the composition of the 

 enzyme preparation. With a given enzyme maltose may be the sole sugar product, with 

 another there may be isomaltose, or maltose and glucose, or isomaltose and glucose, etc., 

 depending upon whether there be a pure maltase present, or emulsin, or maltase with 

 glucase, or maltase with emulsin and glucase, etc., maltase converting dextrin into maltose, 

 emulsin forming isomaltose, and glucase converting maltose and isomaltose into glucose, etc. 



The nature of the products formed by acid hydrolysis are modified by the nature 

 of the acid, the temperature of digestion, etc. ; moreover, the products compared with those 

 formed by enzymes and other agencies are by no means identical. Mulder (Chemie des 

 Bieres, Leipzig, 1858, 166; quoted by W. Nageli in Die Stiirkegruppe, etc., loc. cit.) found 

 that the dextrins formed by the action of malt extract, sulphuric acid, and torrefaction, 

 respectively, differed from one another in their reactions, especially in relation to certain 

 precipitants. 



Soxhlet (Zeit. Spiritindustrie, 1884; quoted by Johnson, Jour. Chem. Soc. Trans., 

 1898, Lxxiii, 490) states that the dextrins resulting from the actions of acids are quite 

 different from those produced by diastase. Diastase, for instance, had no action on the 

 dextrins formed and digestible by acid. Johnson (see page 151) has, however, shown that 

 there is a slight action. Effront (Monit. Scient. f. 1887, 513; Jour. Soc. Chem. Ind., 1889, 

 VI, 733) investigated the products of the saccharification of starch by extract of malt and 

 by acid, and reached the following conclusions: 



(1) The course of the conversion of starch into dextrin and sugar is not the same with 



malt and acid. The saccharification by malt is attended by the decomposition of 

 the starch-molecule into dextrin and maltose, while with acid the conversion is into 

 dextrin and maltose, which in turn are converted into glucose. 



(2) The dextrins formed by malt and acid ai'e not identical; those formed by malt are 



polymeric, while those formed by acid are not. 



(3) The dextrins in both instances have the same rotatory power. 



(4) Maltose is always formed in the saccharification of starch by acid, and the quantity 



increases as saccharification proceeds. In the earlier stages of saccharification there 

 is an almost constant ratio between the quantities of maltose and glucose formed. 

 This is al)out 34 to 38 of maltose to 100 of glucose. 



(5) In the saccharification of starch by malt the formation of glucose is inconstant. While 



glucose almost always occurs in solutions of high gravity, it is only formed in liquids 

 of low gravity if the malt extract employed be turbid. 



In another publication (Enzymes and their Applications, Trans, by Prescot, 1902) 

 Effront states that the dextrins formed by the action of acid have a very low nutritive 



