US2642745A - Method for determining bran in cereal flour - Google Patents

Description

UNITED STAT Patented June 23, 1953 METHOD FOR DETERMINING BRAN IN CEREAL FLOUR Roger A. Larkin, Peoria, 111., assignor to the United States of America as represented by the Secretary of Agriculture NoDrawing. Application July 8, 1952,

v Serial No. 297,800

'IClaims. (o1. 73-432) (Granted under A non-exclusive, irrevocable, royalty-free license in the invention, herein described, for all governmental purposes, throughout the world, with the power to grant sublicenses for such purthe United States of America.

in wheat flour.

a simple dye technique.

flours.

significance.

somewhat empirical in character.

not stain the endosperm cell walls.

the base.

of the solid residue.

may also be present in the solid residue are color- Title 35, U. S. Code (1952),

see. 266) less. The alkali treatment produces a differential decolorization, and the decolorizing action is stopped at a point before bran and germ particles have been decolorized and after the other For example, it

poses, is hereby granted to the Government of materials in the mixture have become colorless.

The bran and germ content of the flour sam- The invention relates to a method for deterple may be determined visually, i. e., by estimatmining the presence of bran and germ particles ng the relative proportion, by countin the It relates, particularly, to. a fragments, or by any other visual method as method for determining such particles in cereal desired. flour or in similar comminuted compositions by The invention possesses several advantages As will be explained in over prior evaluating methods. detail below, the method is more accurate and does not depend upon a gravimetric or other definitive than prior methods for evaluating kind of chemical analysis. It maybe carried out a in considerably less than 2 hours time, requires The degree of refinement of a cereal flour may o special equipment, except a microscope, and be measured by the completeness of theseparadoes not require highly trained personnel. tion of the bran and germ constituents from the The following procedure is a preferred method endosperm and resultant flour. Evaluation of of carrying out the in ti flours to determine the degree of refinement'has 0 1. A Wei e a p e of f o iS Wet with ethlong been a problem of considerable economic anol, preferably 95 percent ethanol.

Prior methods have frequently in- 2. Crystal Violet dye is applied in the form of volved such indirect determinations as ash con- 0.04 to 0.07 percent aqueous solution. Suflicient tent, color tests, or combinations of both. Pentodye should be added to form a watery suspension .san content has also been suggested as a test. or at least a thin slurry.

The prior methods of evaluation have required 3. After permitting the dye mixture to stand complicated and rather tedious techniques and for about 10 minutes. sufllcient 0.25 N sodium have not provided satisfactory criteria, all being hydtroxide is added to disperse the starch and pro em. It has been discovered, in accordancewith this After standing for about 5 minutes, an invention, that Crystal Violet dye when applied app ately equal volume'of distilled water is to a flour sample stains-the germ and the bran added, and the mixture stirred and let stand for layers and protein of the endosperm, but does about 1 hour.

Such a dyed 5. The mixture sample may be treated with a strong base such 1, white filter paper. I as sodium hydroxide or potassium hydroxide in The bran and germ particles appear violet in aqueous solution to leave, the bran and germ color upon the white filter paper. Other matefragments stained distinctively, the remainder rial on the paper which may be minor amounts of the sample having been rendered colorless by f e perm cell walls, incompletely dispersed 40 starch, vor incompletely dispersed protein are Utilizingthese discoveries, a simple procedure colorless. Bran and germ particles are, therehas been developed which affords a rapid and fore, easily identified, and the deposited matereliable determination of the bran and germ conrial maybe observed wet or dry. The detertent of cereal flours or of cereal flour mixtures, m ati may be Conveniently accomplished Visor even of baked or otherwise finished food produally. It may also be accomplished directly or ucts consisting mainly of flour. Intgene'ral, the indirectly by light transmittance, reflectance, method comprises applying a dilute aqueous solucolorimetric methods or similar methods familiar tion of the dye to the sample, subsequent treatto skilled workers. For example, light reflected ment with aqueous alkali andthen separation of from a stained sample may be measured and the liquid medium followed by final observance 5O corded by photoelectric devices as an indication Ihe bran and germ parof the bran content. ticles, after this treatment, app Violet in Slight variations in the timing of various steps or. Endosperm cell walls, incompletely dispersed do not affect the result, and the procedure can be starch and incompletely dispersed protein which completed in about 1 hours. The time may be shortened by permitting the alkali to act for is filtered, preferably using about minutes in the third step, then adding the distilled water and filtering immediately. This variation in procedure must be timed fairly accurately, lest the action of the alkali cause the germ and bran particles to become decolorized.

A useful variation of the invention can be em.- ployed to show the endosperm cell walls in wheat fiour. Approximately 30 minutes'after thewater has been added in the fourth step, one ml. of about 0.1 percent aqueous Congo red stain is added to the mixture. sperm cell wall particles an orange red. 'The sample should be examined in the staining solution. It is not practical to combine the two determinations on the same sample, howeven'ior the bran and germ particles tend to stain orange red after contact with the Congo red for to minutes. Moreover, the filtration with filter paper tends to interfere with the results because the red dye stains the filter paper.

Observation of the violet stained bran and germ particles is preferably carried out microscopically. Both appear about the same under low magnification, but under high magnification, say of about 100X, the bran particles usually appear as fiat pieces, while the germ particles appear as small, irregularly-shaped thick pieces. The evaluation is not absolute, however, for it is difiicult to distinguish between very small particles of bran and of germ. f

The following specific example illustrates the invention.

Example One-gram samples each of patent, first clears and red dog flour were wetted with 95 percent ethyl alcohol. Each sample wasthen mixed with 18 ml. of 0.05 percent Crystal Violet and let stand for 10 minutes. Each was then mixed with 120 ml. of 1.0 percent (025 N) sodium hydroxide and let stand for five minutes, whereupon 140 ml. of distilled water was added and'the mixture let stand for one hour. The mixture was then filtered on No. 1 Whatman filter paper, using a coarse fritted glass funnel.

The filter paper obtained from the red dog sample had a deep violet appearance. Microscopic examination revealed'that the color was due to small particles of bran that had been dyed. The filter paper from the first clears sample was an intermediate shade of violet with a finely mottled appearance, the color being due to the presence of a considerable amount of dyed bran. The filter paper obtained from the patent sample had an overall tint of light violet, caused by individual particles of dyed bran peppered over the paper.

The number of steps set forth above represent preferred procedure. However, it is to be understood that the invention may be carried out in a wide variety of ways. The concentration of Crystal Violet dye must be kept within the designated limits.

Wetting the sample with ethanol or other denaturing agent is usually necessary for satisfactory results, for it prevents pasting and facilitates contact between the dye solution and the sample. It is only necessary that contact between the sample and the dye be sufiiciently long to afford full staining. The amount of sodium hydroxide, or other alkali, may be increased or decreased compared with that specified in the numbered steps. However, the more alkali present, and the stronger it is, the faster the decolorization This stains the endoprocess will be, and it is desirable that decolorization proceed at a rate slow enough to effect substantial decolorization of all substances present except the bran and germ particles.

I claim:

1. A method for determining bran and germ particle constituents in cereal flours comprising treating a given samle of flour material with a 0.04-0.07 percent aqueous solution of Crystal Violet whereby to dye bran and germ particles present in said fiour material together with other material present, effecting differential decolorizing by treating the mixture with an aqueous solution of alkali until substantially all other constituents are decolorized, separating the solid material from the resulting alkaline solution and subsequently determining the amount of bran and germ particle constituents.

2. A method for determining bran and germ particle constituents in cereal flours comprising treating a given sample of flour material containing bran and germ particle constituents with a 0.04-0.07 percent aqueous solution of Crystal Violet whereby to dye at least said bran and germ constituents, treating said dye mixture with aqueous alkali to decolorize and substantially disperse the protein and starch constituents of said flour and separating the solid constituents from the alkaline aqueous solution before the bran and germ constituents become decolorized and subsequently determining the amount of bran and germ constituents.

3. The method comprising wetting a known quantity of cereal flour in aqueous ethanol, adding sufiicient 0.04-0.07 percent aqueous solution of Crystal Violet to color the constituents of said cereal fiour, adding alkali in sufficient quantity to decolorize differentially the starch, protein and endosperm cell wall material with respect to the bran and germ constituents and subsequently separating the colored bran and germ constituents from the aqueous dye solution before said bran and germ constituents undergo substantial decolorizing, and subsequently determining the content of bran and germ constituents by visual observation.

4. The method of claim 1 in which the treatment with aqueous alkali is carried out using 1.0 percent sodium hydroxide.

5. Method of claim 4 in which the alkaline treatment period is about 5 minutes and is followed by dilution of the mixture with about an equal volume of water and the diluted mixture permitted to stand for about 1 hour before separation of the insoluble constituents.

6. Method of claim t in which the alkaline treatment period is approximately 15 minutes followed substantially immediately by dilution with about an equal volume of water.

7. The method of rendering bran and germ particles, derived from cereal grains, visually distinguishable from other components of said cereal grains comprising subjecting a mixture of said particles and said other components to the action of a 0.04-0.07 percent aqueous solution of Crystal Violet dye followed by alkaline decolorization of said other components.

ROGER A. LARKIN.

References Cited in the file of this patent UNITED STATES PATENTS Number

Claims (1)

1. A METHOD FOR DETERMINED BRAN AND GERM PARTICLE CONSTITUENTS IN CEREAL FLOURS COMPRISING TREATING A GIVEN SAMLE OF FLOUR MATERIAL WITH A 0.04-0.07 PERCENT AQUEOUS SOLUTION OF CRYSTAL VIOLET WHEREBY TO DYE BRAN AND GERM PARTICLES PRESENT IN SAID FLOUR MATERIAL TOGETHER WITH OTHER MATERIAL PRESENT, EFFECTING DIFFERENTIAL DECOLORIZING BY TREATING THE MIXTURE WITH AN AQUEOUS SOLUTION OF ALKALI UNTIL SUBSTANTIALLY ALL OTHER CONSTITUENTS ARE DECOLORIZED, SEPARATING THE SOLID MATERIAL FROM THE RESULTING ALKALINE SOLUTION AND SUBSEQUENTLY DETERMINING THE AMOUNT OF BRAN AND GERM PARTICLE CONSTITUENTS.