SOLUBLE STARCH. 101 



actcrized by the chief decomposition products present and by the reactions with iodine. 

 No account has been taken of residue. The scheme is, of course, modifiable under difier- 

 ent conditions of experiment. Thus, the final product may be maltose and not maltose 

 and glucose, or glucose; and instead of maltose there may be isomaltose; and in some 

 reactions saccharose and other sugars would be present, etc.; according to some investi- 

 gators either or both amylodextrin and maltodextrin would be included, etc. The color 

 reactions of the second stage will vary in accordance with the nature of the decomposing 

 agent and other conditions. 



SOLUBLE STAKCH, KEVEKTED STARCH, COAGULATED STARCH, "ARTH-ICIAL STARCH," AND 



" ARTIFICIAL STARCH-GRAINS." 



SOLUBLE STAKCH. 



The term soluble starch has been used so indiscriminately that it not only does not 

 designate any specific body, but it may also apply to a substance so close to raw starch as to 

 give the typical blue reaction with iodine, or to one that is a mixture of starch and ery- 

 throdextrin, or to a specific body that has properties of both starch and erythrodextrin, 

 or to solutions of dextrins or dextrin and sugar, etc., which are so far removed from starch 

 as to give no color reaction with iodine. In other words, it has been used to signify the 

 products of decomposition as they exist at any given stage of the process of saccharifica- 

 tion from the first modification product to a mixture of achroodextrin, or to "malto- 

 dextrin," in which there may not be a particle of starch, soluble or insoluble, present. 

 Obviously the term soluble starch should be restricted to the first i^roduct which yields 

 a blue reaction with iodine. Boiled starches are essentially pseudo-solutions which con- 

 tain small and variable quantities of chssolved particles of starch, together with a relati\'ely 

 great mass of suspended particles which represent starch in many degrees of molecular 

 condensation. Such pseudo-solutions may be rendered into perfect solutions in proportion 

 to the extent of solution of the suspended particles, so that by appropriate procediu'es 

 a non-colloidal solution of starch can be obtained which can be filtered through a colloidal 

 membrane or a Chamberland filter. Pseudo-solutions, such as starch-paste or less dense 

 preparations, can be converted into a clear limpid solution, or true soluble starch, by minute 

 quantities of amyloclastic enzymes, by small or large quantities of amyloclastic enzymes 

 that have been modified by subjection to a temperature of 75° to 80° for 10 to 15 minutes, 

 by the actions of dilute acids and other chemical agents, and by heating in the autoclave 

 at about 140°. 



Starch-paste, starch pseudo-solutions, and starch non-colloidal solutions undergo, 

 upon standing, or upon repeated heating and cooling, more or less reversion to insoluble 

 forms of starch. This change becomes apparent at first as a turbidity, which grows 

 more marked as condensation proceeds, and which ultimately may be observed in the form 

 of granules which have the appearance and general properties of starch-grains. This 

 reversion product has been termed amylocellulose, or coagulated starch, or artificial starch, 

 or artificial starch-grains. There seem to be many forms of this reverted substance which 

 differ in solubiUty, digestibility, reaction with iodine, etc. A similar reversion may be caused 

 by a specific enzyme that has been named coagulasc, but the reversion products are not 

 absolutely identical with those formed spontaneously (see page 111). 



Probably the earliest investigator to prepare soluble starch was Guibourt (Ann. de 

 chim. et phys., 182S, xl, 183). This he did by pounding starch-grains in a mortar and 

 placing in water. The rupture of the grains renders them partially soluble in cold water, 

 giving rise to a gelatinous solution that yields a blue reaction with iodine. This observa- 

 tion has been repeated by many investigators, and while it has been held by some that 

 the gelatinization is due to heat formed during the pulverization, this assumption has 

 been totally disproved (page 28), and it has, moreover, been clearly shown by the records 



