1.F = (a-1) b / 27Further: 1. The desired quantity of fat equal is to the R.M.N. a, of the total fat less that of the cacao fat (1·0) multiplied by the total amount of fat and divided by the average R.M.N. for butter fats = 27.2.a) E = 1·11 K2. The total amount of albumen E is equal to the amount of caseine K multiplied by 1·11, as this constitutes about 90% of the former; and as the albumen E, milk sugar M and the mineral constituents A (Ash V) are present in the milk in the proportion of 100 : 132 : 21·4, this yields the formula given in b & c.b) M = ( 1·11 K - 132) / 100c) A = (1·11 K - 21.4) / 1003.T = F + E + M + A3. The total quantity of milk stuff T is equal to the total of fatty contents, albumen, milk, sugar and ash.4.x = Q · k4. The fatty constituency of the original milk or cream to be calculated from the formula x = Q times k, where Q is the quotient resulting when the amount of fat F is divided by that of caseine K, and k the normal caseine consistency of average milk preparation. Or it varies as the numbers k1etc. indicate in the case of 10% cream and so forth. Higher percentages than those given do not come into consideration.Q = F / Kk = const.In the case of milk:k1= 3·15k2= 3·05k3= 2·7k4= 2·5
c. Microscopic-botanical investigation.
Fig. 100.
Fig. 100.
A.Parenchyma of the cotyledon after removal of fat and treatment with Iodine chloral hydrate, a: parenchyma cells with starch, b: with cacao red.
B.Aleuron particles with globois (Molisch) from parenchyma cells.
Fig. 101.
Fig. 101.
A.Mitscherlich particles.B.Seed cells, above with starch bodies, underneath with violet colouring matter (cacao red) lying in chloral.C.Series of yeast germs.D.Threads of extraneous growth.E.Epidermis and layer of cells occurring on the outer shell (enlarged 340 times).
A.Mitscherlich particles.
B.Seed cells, above with starch bodies, underneath with violet colouring matter (cacao red) lying in chloral.
C.Series of yeast germs.
D.Threads of extraneous growth.
E.Epidermis and layer of cells occurring on the outer shell (enlarged 340 times).
Cacao is to no great extent particularly characterised anatomically. The parenchyma cells fig. 100 are chiefly to be noticed, containing either fat, albumin (protoplasm) aleuron granules, pigment, or cacao starch. Thestarch, as already remarked, consists of especially small globular granules, mostly separate, but also two or three adherent. It is somewhat more difficult to gelatinise than other kinds of starch, and it is coloured blue by iodine somewhat more slowly than many other starch granules, especially in the preparations containing fat. Cacao preparations which have been disintegrated by fixed alcalis, differ in this respect; according to Welmans, iodine first forms colourless iodine compounds, and not until the alkali has been saturated, is the blue colour developed. In such cases, care must be taken, that an excess of iodine is present. In estimating the amount of foreign starch, great care must be taken that the conspicuous bluish-black granules of the foreign starch, which immediately strikethe eye, are not over estimated, which may easily occur. For control observations, mixtures containing various known amounts of starch should be tried comparatively. The pigment cells and the epidermis with the Mitscherlich’s particles (figs 101 and 102) should be noticed as well as the characteristic globoids, which occur in the ash of the cotyledon tissues (compare page 67). Theoutside shell, more or less woody according to the origin of the bean, consists of four layers of cells; this is best recognised by the large cells of the principal tissue, which are distinguished by their form as well as by their thickened side walls from the tissue of the cotyledon. Another characteristic of this layer consists of the large number of coarse spiral vessels, which exceed those of the seed lobes in size, and finally, the inner elements of the stone cell layer, which, however, on account of their limited development are seldom to be discovered. The smooth, fine brown coloured, and light refracting fragments, which frequently appear quite structureless and have their fibrous character made perceptible only after treatment with caustic alkali, must be regarded as characteristic of the inner part of the husk or the seed membrane. The best observing medium is a solution of chloral hydrate or almond oil, as well as dilute sulphuric acid and glycerine.205The substance is always to be defatted with ether, before the microscopical examination. A complete extraction of the fat, according to Welmans, can occur only with exceedingly thin cuttings, in which every cell of the section would be operated on, or in powdered preparations, when the cells have been completelytorn asunder by mechanical pulverisation. The fat is not extracted by solvents from intact cells, as the cell walls are impermeable by them.206
The detection offoreign starchis possible only by use of the microscope; by means of standard preparations an approximate estimate may be made as to the amount and kind of meal added.207The examination of starch is especially facilitated by H. Leffmann and W. Beam’s208centrifugal method: the sample suspended in water is subjected to rotation for a short time in the centrifugal apparatus. The presence of foreign starch is shown by a white layer in the resulting sediment. This layer can be collected and microscopically examined for foreign starch and husk. In the case of cacao preparations, it is always well to distinguish between unimportant traces and quantities that justify objection.209
Fig. 102.
Fig. 102.
A.Silver membrane with the hairs (Mitscherlich particles)tr, and the crystalsfandK.
B.Cocoa powder:cCotyledon tissue with cells of fat and colouring matter,pshell parenchyma,spsperiods,dlayer of dry cells.
A means of detectingtragacanthin cacao preparations, has lately been described by Welmans210. 5 grammes of the cacao preparation are to be mixed with sufficient dilute sulphuric acid (1: 3) to form a thick pulp, then with 10 drops of solution of iodine (inpotassium iodide) and some glycerine. A portion of the mixture is examined under the microscope (enlarged 160 times). The entire field of view now appears to be thickly sown with countless blue dots, some globular, others irregular, among which are especially to be noticed the large tragacanth cells, resembling potato starch, which are not seen in cocoa powder that is free from tragacanth, when similarly prepared as an object; the small blue dots, due to cacao starch, are visible only in the densely occupied portions.
An admixture of thecarob, which has been seldom observed, can be easily recognised under the microscope by the characteristic reddish wrinkled tubes of the fruit pulp, which are also coloured violet by treatment with a warm solution of caustic potash.
The presence ofearth-nut or earth-nut cakecan be detected by the aid of the microscope on treatment with chloral hydrate, by the characteristic saw toothed epidermis cells of the husk of arachis seed.
Hazelnut and walnut pulp, so far as they are to be met with in cacao preparations, can be distinguished under the microscope by shreds of the tissue of the seed husks, in which broad streaks of spiral vessels, lying close on one another, are distinctly prominent. If in addition the woody fruit shell be admixed, it can be detected by the great number of cells.