The calculation of the botanical composition of wheat flours and offals from the chemical analysis
Authors: Straub J. , Hekker Th. 
Published: September 2010

In the framework of a joint investigation into the composition of industrial wheat milling fractions our object was the botanical analysis thereof, that is the determination of the amounts of the various tissues present. We started from the assumption that virtually only the endosperm contains starch, only the aleurone phosphate (actually phytin phosphate), the fruitwall with the testa crude fibre. From determinations of the starch, phosphate and crude fibre content in the fractions the percentages of endosperm, aleurone and fruitwall could be calculated. The endosperm was found to consist of two sharply distinguishable parts, the inner and the outer endosperm. The embryo content was neglected, moreover in milling the scutellum tissue was probably mixed with the outer endosperm. The method is recommended for use in mill inspection, in particular for judging of the efficiency of individual machines.

Par. I in table I gives a summary of the milling fractions, their yields and the analytical figures used. The figures for the separate milling fractions give linear equations (par. 2) from which one can calculate: the starch content of outer endosperm tissue (55.5%), the phosphate content of aleurone tissue (15%), the crude fibre content of fruit wall tissue (22%, all on a base of 15% of moisture).

The calculation is made graphically (par. 3, fig. 1), From these figures the botanical composition of the milling fractions (table II, corrected table III) follows directly (par. 4).

The joint results for all milling fractions have been collected in a triangular diagram (fig. 4), which depicts the gradual shift in the composition of the fractions. The figures lead to the “botanical balance”: the comparison of the total of the tissue constituents of the grain (8.3% pericarp, 6.3% aleurone, 83.9% endosperm, 1.5% embryo) with the sum of these constituents in the milling fractions.

In par. 5 it is shown, how on the basis of the results of the botanical analysis it is possible to find out in what manner chemical constituents that occur in more than one type of tissue, are distributed over said tissues and what percentage of each constituent a certain type of tissue contains. Thus aleurone is found to contain 25.0% protein and 9.6% of fat, outer endosperm (plus some scutellum tissue?) 19.4% and 5.6% respectively, inner endosperm 8.8% and 1.5%. The equations set up are again solved graphically (fig. 2 and 3).

In par. 6 a new rectangular graphical representation of the results of the botanical analysis of all the successive fractions is described (fig. 5). In this representation the curve showing the content of any chemical constituent in the fractions can also be drawn and thus an impression can be obtained how this constituent is distributed over the types of tissue. It may then for example appear whether particular substances of a very specific character (oligo‐elements vitamins, enzymes) are also specific to a single type of tissue. The graph is used by us in the discussion of the protein content and the distinction of outer and inner endosperm. In par. 7 our results are compared with those appearing from the technical literature.