Examination of Elm Bark, Flaxseed and Mustard for Starch.
By J. U. Lloyd. [For valuable assistance in detail work, the thanks of the author are extended to Dr. Sigmond Waldbott.]
Presented to the Amer. Pharm. Assoc, Denver meeting, 1895.
Owing to the alterations in our library building, necessitating the storing of its contents, it is impossible for me to refer to the literature connected with this subject. References thereto will, perhaps, be added later.
The immediate object is a consideration of the subject of starch in connection with the aforenamed substances, a subject now of great importance to Ohio pharmacists. The question is, does elm bark contain starch at all; do flaxseed and mustard, if free from starch-bearing seeds, ever contain starch, and is it practical in commerce to apply the rigid tests of the Pharmacopoeia to ground flaxseed and powdered mustard?
In Chem. Zeitung, 1890, p. 688, the following statement is found, coming from Prof. Hilger, in Erlangen:
"Small quantities of starch grains, of various origin, if found in ground spices, should not, by necessity, detract from their being considered as honest goods in trade."
The inner bark of Ulmus fulva, Michaus (nat. ord. Urticaceae).
In flat pieces, varying in length and width, about 3 mm. thick, tough, pale brownish-white, the inner surface finely ridged; fracture fibrous and mealy; the transverse section delicately checkered; odor slight, peculiar; taste mucilaginous, insipid.—U. S. P.
It will be observed that no chemical test is given by which we can be governed concerning adulteration of the powdered bark. In referring to other authorities, little information is to be found, and even their brief statements concerning the presence of starch do not agree. Since the larger share of elm is consumed as powdered elm, and since druggists do not powder it, but rely altogether on trade millers, the subject of simple tests and rules as to purity are now, in Ohio, at least, of great importance. In the face of conflicting reports made by advocates who claim that elm bark does not contain starch, and those who claim that it does contain starch, these results are offered simply as voicing the result of my personal experimentation on this now important subject.
If a slab of dried elm bark be split longitudinally, and the exposed edges moistened with very weak iodine tincture, a light purplish-blue color, more or less prominent, follows, which disappears quickly. If the bark be previously moistened with dilute sulphuric acid, the blue color is quite permanent. The same is true when it is moistened with a dilute solution of iodine in iodide of potassium, acidulated with sulphuric acid. Ten specimens taken by me at random from a lot of Wisconsin bark, and others from Kentucky and Ohio, demonstrated that all of them would respond to the test, and I have found none that did not do so, although some specimens of bark contain more starch than others. If a thin shaving, not of the inner side of a slab of elm, be dropped into a dilute solution of iodine in iodide of potassium, made acid with sulphuric acid, the shaving will usually turn blue, or become streaked with blue, although, as the inner surface of the bark is often free from starch, the shaving must be from beneath the surface. In this connection it should be added that this starch-free layer is of varying thickness, sometimes being a mere film, again (seldom) forming the bulk of the bark. Under these conditions, it is to be presumed that enough starch must be present in powdered elm to make it respond to the iodine test.
To Detect Starch.—Powder the elm bark, and thoroughly mix 1 gramme with 100 c.c. of water, by rubbing in a mortar, the water being gradually added; then boil.
To 2 c.c. iodine test solution, U. S. P., add 8 c.c. 10 per cent. sulphuric acid.
Mix 1 c.c. of the iodine mixture with 8 c.c. of the cold mucilage; a clear, quite permanent blue color will be produced. If iodine tincture without acid be added to the mucilage, the blue color will be developed, but disappears quickly. If the mucilage is to be made of the whole bark, shave it transversely into thin shavings, put 1 gramme into a capacious mortar and rub constantly with 100 c.c. of boiling water, gradually added, until a thick mucilage results.
The coloration that results in presence of too much iodine is not bright blue, for if an excess of iodine is used, a shade of purple or brownish yellow results. It is essential that no excess of iodine be employed, and, when the yellowish shade results, additional mucilage must be added to counteract the excess.
Incineration of seven specimens showed the presence of 8.62, 9.13, 9.22, 7.64, 8.10, 8.08, 10.10 per cent. of ash respectively, the average being 8.69 per cent.; observed maximum, 10.10 per cent.; observed minimum, 7.64 per cent. Each of the foregoing results is the average of several incinerations of the same specimens of bark, which agreed very closely.
Elm bark contains starch, enough to respond to the iodine test, and this fact should be stated in the Pharmacopoeia. It should also be stated that when powdered elm is boiled with water the mucilage, if acidulated with sulphuric acid, on the addition of dilute iodine solution, should turn blue, and retain its color for some time. Elm bark contains so little starch that, in my opinion, a comparative test can be easily devised that will determine any fraudulent admixture of starch, and in justice to the trade a method to detect added starch should be recorded in the Pharmacopoeia. The Pharmacopoeia should also limit the amount of ash.
Elm bark contains a natural constituent, capable of disturbing the iodine starch test, for if a blue solution, made by adding freshly prepared iodide of starch to water to distinct coloration, be mixed with its bulk of mucilage of elm, the mixture will be immediately decolorized. The blue color will be partly restored by the addition of dilute sulphuric acid.
According to preliminary experiments this phenomenon is most probably due to the presence of both tannin and an organic calcium compound, which may be isolated from the bark. Report on these constituents is reserved for the future.
The seed of Linum usitatissimum, Linne. (nat. ord. Lineae).
About 4 or 5 mm. long, oblong-ovate, flattened, obliquely pointed at one end, brown, glossy, covered with a transparent, mucilaginous epithelium, which swells considerably in water; the embryo whitish, or pale greenish, with two large, oily, plano-convex cotyledons, and a thin perisperm; inodorous; taste, mucilaginous, oily and bitter.
Ground linseed (linseed meal or flaxseed meal) for medicinal purposes should be recently prepared, free from unpleasant or rancid odor. When extracted with carbon disulphide, it should yield not less than 25 per cent. of fixed oil.
The filtered infusion of ground linseed, prepared with boiling water and allowed to cool, has an insipid, mucilaginous taste, and should not be colored blue by iodine T. S. (absence of starch).—U. S. P.
In this connection, as no exception has been made to the statement concerning the proportion of oil, that substance is herein neglected.
As regards the starch, the statement has been made that immature flaxseed contains that substance, a point that I have had no opportunity to verify. With a view to establishing the fact as to whether commercial flaxseed contains starch, a number of samples of selected flaxseed were tested. In no case could starch be found.
Upon testing the ground flaxseed of the market, however, it was found that every specimen examined responded to the starch test, some contained starch in very large amounts, and it was not without surprise that the fact was shown that the ground flaxseed sold to my own establishment had been grossly adulterated and contained at least 20 per cent. of starch. Neither was it less of a surprise to find that flaxseed ground by responsible parties and offered as pure, and believed by them to be pure, gave a decided blue coloration, and would not conform to the demands of the Ohio Pure Food and Drug Commissioner. Upon investigation it was found that flaxseed is often mixed with such cereals as rye and wheat, and that growing fields of flax are often largely contaminated with volunteer cereals. In addition, the seed is often put into meal and flour sacks and becomes impure thereby. The farmer does not, cannot, separate these foreign seeds, the oil miller cares little, if at all, for the contamination, and hence, since linseed oil makers are the parties who produce the ground flaxseed of commerce, and grind for market the quality of seed they press for oil, it is readily seen that commercial ground flaxseed cannot be expected to withstand a searching starch test. Of course, these remarks do not apply to mixtures designed intentionally as adulterations. That flaxseed can be cleaned in quantities is, however, shown by the fact that in wholesale seed stores in Cincinnati I have succeeded in picking up flaxseed free from starch-bearing contaminations.
It is my opinion that if a universal demand arises for pure flaxseed meal it will be followed by a trade supply that will conform to the starch test of the Pharmacopoeia, but naturally at increased price.
The pharmacopoeial test is, I believe, objectionable by reason of the unnecessary direction to filter the infusion, which, owing to its mucilaginous nature, is troublesome to say the least. It may also be made more specific as to details, and, owing to the growing importance of this subject, nothing should be left to conjecture.
The test as I apply it is as follows:
Boil 1 gramme of ground flaxseed with 20 c.c. of water, and cool.
Mix 0.2 c.c. test solution of iodine, U. S. P., with 10 c.c. of 10 per cent. sulphuric acid.
To 8 c.c. of the flaxseed mucilage add 2 c.c. of this iodine compound, when, if starch is present, a blue coloration will result. As little as 0.5 per cent. of starch is indicated by a strong reaction.
An admixture of but 0.3 per cent. of starch is easily recognizable by this iodine test. Even the presence of as little as 0.1 per cent. of starch may also be recognized by making the mucilage more concentrated, using only 10 c.c. of water, instead of 20 c.c, to 1 gramme of flaxseed.
Free from starch.— U. S. P.
If commercial mustard seed be examined it will be found, as a rule, mixed with foreign seeds. Among these are to be found starch-bearing seeds, especially the seed of Chenopodium (American wormseed), this being often present and containing much starch.
If this mixed mustard be powdered and tested by the usual iodine method with small amounts of iodine, it will be found, even in the presence of much starch paste, that the reaction will be indistinct or evanescent, if it develop at all. This is due to the action of iodine on volatile mustard oil. In this connection it may be said that when a few drops of oil of mustard are stirred into an excess of iodized starch mixture, the blue coloration will soon be removed.
As a result of a series of experiments that were made in order to arrive at an expeditious method to eliminate the iodine-absorbing power of mustard oil prior to the testing for starch, the following process gave the greatest satisfaction:
Put into a large test tube 0.5 gramme of the ground mustard seed, add 8 c.c. of water and 1 c.c. iodine test solution, U. S. P. Boil until the brown color has disappeared. Decant, cool the decanted liquid, and add, by means of a pipette, one drop of the iodine test solution, U. S. P. If as little as 0.1 per cent. of starch be present, a distinct and quite permanent blue or greenish-blue color will appear.
If the principle of boiling the infusion of mustard seed with the iodine solution be not adhered to, the starch reaction will be evanescent, even in the case of gross admixtures of flour.
As the Pharmacopoeia demands that no starch be present (and I can find none in pure mustard seed), it should be shown explicitly how the presence of starch can be determined.
Elm bark contains starch.
Flaxseed and mustard, both white and black, free from admixture, do not contain starch.
The presence of small amounts of some foreign seeds that are difficult to separate, and of grains of cereals, are common in both flaxseed and mustard, and generally carry sufficient starch to make the powder respond to starch tests, if properly applied.
In the case of elm bark, the blue coloration disappears very quickly unless acid is added. After this blue color has faded, it can be partly revived by the addition of sulphuric acid.
With mustard, the blue color also disappears, if an insufficient amount of iodine be added, because the latter is readily assimilated by the volatile oil of mustard, even in the presence of a large amount of starch. Sulphuric acid does not revive the blue coloration; but previous heating with an excess of iodine test solution saturates the mustard oil, and renders the starch reaction quite permanent.
With flaxseed, the blue coloration of starch remains for some time, but in contradistinction to the behavior of mustard, an excess of iodine must be avoided, in order to obtain the pure blue color of iodide of starch. In commerce, ground flaxseed is not, so far as I know, supplied starch-free, but it can be easily obtained without any intentional admixture. Ground mustard now and then is pure, but, owing to unintentional contaminations, it usually responds to the starch test, if properly applied. It can easily be purchased free from adulteration, but not necessarily entirely free from starch-bearing seeds.
In no case is it desirable to attempt to filter any of these mucilages, the Pharmacopoeial directions to this effect being, in my opinion, objectionable.