Degree Type


Date of Award


Degree Name

Doctor of Philosophy




The various factors affecting the estimation of starch by determining the glucose formed by acid hydrolysis following enzymatic hydrolysis have been studied. The effect of grinding of the plant material was shown to be important. Insufficient grinding leads to low values in starch, and grinding in the ball mill caused a breakdown of starch, and probably of non-starch interfering substances, to more soluble material;Gelatinization is necessary to extract starch from plant tissue. Probably vigorous conditions are not needed, but autoclaving for one hour at 15 pounds had no detrimental effect on starch recovery;Salivary diastase is preferred to taka-diastase in the enzymatic digestion. It is better to use a short incubation time to decrease the danger of bacterial activity;Clearing of the enzymatic extracts is essential to remove certain interfering substances. Even when this is done, however, not all the interfering substances are removed and results are sometimes high. After clearing, it is necessary to delead. It is important not to use too large an excess of K2HPO 4 for this purpose;In the acid hydrolysis the HCl concentration must be kept lour enough so that the NaCl formed on neutralization will not give a high sugar titration. The condition necessary for complete hydrolysis is 1 + 80 HCl heated in an autoclave at 15 pounds pressure for 30--60 minutes;Certain optimum conditions were determined for the estimation of starch: (1) Grinding to pass through a 40 to 80 mesh screen; (2) Gelatinization in an autoclave for 30 minutes at 15 pounds pressure; (3) Incubation of the sample with +/-3ml of 50 percent saliva for two hours; (4) Clearing with lead acetate, filtering and deleading with a slight excess K2HPO 4; (5) Hydrolysis of the extract with 1 + 80 HCl at 15 pounds for 30--60 minutes;Determination of the reducing sugars formed.



Digital Repository @ Iowa State University,

Copyright Owner

Robert Delafield Powell



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68 pages