168 DIFFERENTIATION AND SPECIFICITY OF STARCHES. 



THE ASH. 



The phosphates of the starch-grains have attracted especial attention because of their 

 giving, it is believed, an acid reaction to certain kinds of starches ; because of their assinned 

 effect upon the rapidity of the decomposition of starches by enzymes ; and, finally, because 

 of significant different percentages in starches from different sources and in different grains 

 and parts of the same grain. The relation of the phosphates to the reaction of the grains 

 will be referred to in a subsequent paragraph. The asserted effect upon enzymic processes 

 has been a matter of dispute. 



Effront (Enzymes and their Applications, trans, by Prescott, 1902, 118) records that the 

 addition of 0.5 gram of acid calcium phosphate to 100 c.c. of boiled starch increased the sac- 

 charifying power of an infusion of malt 5.3 times, and that 0.7 gram of ammonium phosphate 

 caused an increase of 6 times. It has been noted by a number of investigators that the 

 addition of very small amounts of certain acids or acid salts is favorable to enzymic activity. 



Fernbach (Woch. f. Brau., 1900, xvii, 35; Jour. Soc. Chem. Ind., 1900, xix, 260) notes 

 that Ling and other investigators found that diastatic activity is increased by small quan- 

 tities of acid and that a distinction must be made between acid salts and free acids. In 

 comparative experiments with increasing additions of acids, it was found that except- 

 ing small quantities of acid phosphate the effect was injurious. Phosphates, he records, 

 have a specific action on the velocity of saccharification. Neutral (dibasic) phosphates 

 are alkaline to methyl orange, and they have a harmful effect on saccharification. Dias- 

 tase was found to act best in a medium that has a neutral reaction to methyl orange, 

 therefore acid phosphates (monobasic) are favorable, while free acid is harmful. 



Fernbach and Hubert (Compt. rend., 1900, cxxxi, 293) found that the primary action 

 of alkaline phosphates is to increase the activity of malt diastase, and the secondary action 

 is to decrease activity. They ascertained that during both primary and secondary actions 

 the reaction of the preparations was acid to phenolpthaleine and alkaline to methyl orange. 



Ford (Jour. Soc. Chem. Industry, 1904, xxiii, 414), in reviewing the subject, states 

 that in his opinion the favorable effect of the acid is not due to the acid alone, but to 

 its neutralizing alkaline impurities, which have a powerful inhibiting effect on diastatic 

 action, and that when these are more or less neutralized the action approaches its normal 

 maximum, which takes place in a neutral medium, or at least one in which the free hy- 

 drions or hydroions are at a minimum. Ford found that ordinary preparations of soluble 

 starch invariably contain phosphates and possible traces of organic phosphorus compounds 

 which are not removed by prolonged treatment with dilute alkali or acid, or washing with 

 water. He holds that the acid phosphates constitute a negligible amount of acidity to 

 starch-solutions, and that they may be looked upon as neutral salts. Maize, wheat, and 

 rice starch contain less or are more easily freed from phosphorus compounds than potato 

 starch, and Ford states that he had prepared from maize specimens which are close 

 approximations to the pure substance. 



An especial degree of importance seems to have been attached to the phosphorus 

 content of starch by the investigations of Fernbach (Compt. rend., 1904, cxxxviii, 428), 

 who found that large grains and small grains of potato starch differ materially in the 

 percentage of phosphorus. For every 100 grams of large and small grains he found the 

 following proportions of PjO^, expressed in milligrams: 160-199, 143-158, 159-185, 160- 

 194, 178-226, and 138-215, the proportions in the larger heavier grains to the smaller 

 lighter grains being 100 : 110 to 115. Regarding the smaller grains as being young grains 

 (see page 180) he arrives at the conclusion that the mature starch-grain consists of a nu- 

 cleus that is relatively rich in phosphorus which becomes during the course of growth 

 covered with laj^ers free from j^liosjihorus, and which constitute the larger portion of the 

 grain. The differentiation of the small young grains from the later deposited layers has 

 also been shown by means of aniline dyes (page 57). 



