996 
Journal of A gricultural Research v < a . xxra, No.» 
An accurate method for the determination of starch in linseed by¬ 
products could be used also to determine starch in apple pomace and 
other pectin-bearing materials. It would doubtless be of value also to 
analysts engaged in researches in dietetics, in determining the starch 
content of diabetic foods containing troublesome plant slimes and 
mucilages, for example. 
There are two serious difficulties in the determination of starch in 
material like linseed meal: (a) It is nearly impossible to effect the pre¬ 
liminary elimination of sugars 5 and other interfering carbohydrates by 
extraction with cold water or io per cent alcohol, as required in the of¬ 
ficial methods (/, p. 95-96), because the mucilaginous substances present 
in linseed meal form an almost impervious layer on the filter, greatly 
retarding percolation, if not preventing it. (b) Linseed mucilage, like 
other vegetable mucilages and pectins, is a polysaccharid, and must be 
excluded from the material subjected to acid hydrolysis. Otherwise 
it will yield reducing sugars, thereby increasing the apparent starch 
content. 
The official direct acid hydrolysis method is therefore barred from 
use at the outset. The official malt-diastase method, based on selective 
carbohydrate hydrolysis, 6 can not be employed because of the first 
difficulty mentioned. Even if the problem of washing out interfering 
sugars be solved, after the malt digestion the mucilage has lost none of 
its capacity for obstructing filtration and it is practically impossible to 
separate the starch conversion products from the rest of the material in 
aqueous solution. 
There are, of course, colorimetric methods, in which advantage is 
taken of the blue color of the compounds of starch with iodin. One 
of the most promising modifications of this type, that of Cassal (2), 
was employed in estimating the starch content of apple pomace. Because 
of differences in the quality of color obtained and consequent difficulty 
in establishing an accurate comparison between the depth of this color 
and that of the starch-iodin standard, however, it was thought that 
this type of method could not meet the requirements in accuracy and 
dependability. 
EXPERIMENTAL 
PRELIMINARY METHOD 
Because of its coagulating effect on colloidal polysaccharids, such as 
pectins, mucilages, etc., strong alcohol can be used to eliminate these 
substances by precipitation, after conversion of the starch by selective 
enzyms. For this to be of value, however, the starch conversion prod¬ 
ucts must remain in solution in the same strong alcohol. 
The work of Davis and Daish (3) indicated that by employing taka- 
diastase as the amylolytic enzym this condition could be fulfilled. 
These investigators reported that by digesting with taka-diastase at 
38°C. for a sufficient length of time, starch is quantitatively converted 
into maltose and dextrose, and into these sugars only. Neville (5) has 
shown that this enzym has no effect on linseed mucilage, and Schneider 
(6) reported that it does not hydrolyze apple pectin. 
6 linseed meal normally contains from 3 to 4 per cent of nonreducing sugars, calculated as sucrose. A 
trace of reducing sugars is usually present. Similar results have been reported by Van Kampen(7). 
• The mucilage of linseed meal is not hydrolyzed by the diastase of barley malt, according to Neville (5) 
nor is apple marc and its pectin, according to Schneider ( 6 ). 
