SACCHARIFICATION OF STARCH 



123 



A method of starch estimation due to von Fellenberg* 

 depends on the solution of the starch in a hot solution of 

 calcium chloride, its precipitation by iodine and the decom- 

 position of the iodine precipitate by alcohol. 



DEXTRINS. 



The term dextrin is applied to substances which are poly- 

 meric with starch and are formed from it by the action of heat 

 alone or of diastase or mineral acids. In the plant dextrins 

 may occur as transitory substances whenever starch is being 

 acted upon by diastase ; further, certain dextrins may occur in 

 a more permanent form. Thus the sap of the epidermal cells 

 of Arum italicum turn reddish-violet on the application of 

 iodine. The aqueous extract of such cells gives on evapora- 

 tion a transparent sticky substance. This also gives with 

 iodine a violet coloration ; after boiling, the colour reaction 

 with iodine is red, and alter digestion with diastase a reducing 

 sugar is found. A similar substance termed soluble starch 

 has been described as occurring in the epidermis of Saponaria 

 officinalis and also in Fungi. It must, however, be borne in 

 mind that the glucoside saponarin, j- C 21 H 24 O 12 , is not un- 

 common in the epidermis of leaves of many plants, e.g. Sapon- 

 aria officinalis itself, and as if gives a blue to violet coloration 

 with iodine it is not unlikely that, in some cases, what has 

 been described as soluble starch is really saponarin. 



As already mentioned, the question of the formation of 

 dextrins from starch by the action of diastase has been the 

 subject of a great many researches, and has, at different times, 

 resulted in the postulation of the existence of a large variety 

 of dextrins and intermediate products, such as amylo-, achroo-, 

 erythro-, and malto-dextrin, amylases, amyloins, glyco- 

 amylins, etc., many of which did not survive for long. 



The chief facts observed during the action of malt extract 

 on starch may be very briefly summarized as follows. If, say, 

 a 10 per cent starch paste is left in contact with malt extract 

 at 50, the mass rapidly liquefies and the solution acquires a 



* v. Fellenberg : " Mitt. Lebensm. Hyg.," 1916, 7, 369. 

 t Barger : " Ber. deut. chem. Gesells," 1902, 35, 1296. 



