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husk may be observed, under the microscope, to consist

Inner substance.

(Mag. 290 diam.).

Outer husk.

especially of tubular fibres, whilst the substance of the seed is composed of minute cells, the cavities of which are filled with starch corpuscles and fatty matters. Cocoa is sold in this country, under the names flake, rock, granulated, soluble, dietetic, homœopathic, &c.

Adulterations of cocoa.-Chocolate or Cocoa is adulterated (according to Mitchell) with flour, potato starch, and sugar, together with cocoa-nut oil, lard, and tallow. Even the so-called finest chocolate is occasionally made up with clarified mutton suet and common sugar, together with ordinary cocoa. The mineral substances employed in preparing chocolate may be red and yellow ochre, minium (red lead), vermilion, sulphate of lime, chalk, &c.

Normandy has known cocoa powder made of potato starch, moistened with a decoction of cocoa-nut shells and sweetened with treacle, and also chocolate, made of the same materials, with the addition of tallow and ochre; he has also met with chocolate in which brick dust and red ochre had been introduced to the extent of twelve per cent., another sample contained 22 per cent. of peroxide of iron, the rest being starch, cocoa-nuts with their shells, and tallow.

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Animal fats and oils.-Method employed by the Commission of the Lancet'1 for their detection: boil the cocoa in water and examine the quantity and nature of the fatty substance floating on the surface, when cool. If half an ounce of cocoa boiled for ten minutes with ten ounces of water, in an open vessel, yields more than sixty-five grains of con1 See Food and its Adulterations,' by Dr. Hassall, p. 213.

In

crete fat, it is probably adulterated with fatty matters. cases where no excess of fats is observed, let the appearance of the fat globules be examined; if these are numerous, firm, shot-like, and globular, (except on the upper surface, which is slightly flattened,) and very small, rarely exceeding the twelfth of an inch in diameter, there is no doubt but that the globules in question consist of the fat or butter proper to cocoa. If the globules be large, flat or disc-like, and exceed considerably the above size, some of them attaining to one fourth of an inch, and even more in diameter, then animal fat or oil is probably present, a conclusion which may be still further confirmed by keeping the fat for some time exposed freely to the air, and observing whether it becomes rancid or not.

From experiments instituted by the Analytical Commission of the Lancet,' it appears that the presence of neither sugar nor starch modifies very considerably the size and form of the fatty globules of cocoa, although less fat, especially when starch is used, collects on the surface.

Starch.-If the amount of starch in cocoa be very great, a cold decoction of cocoa will be thick or jelly-like. The nature of the starch will be determined at once by the microscopical examination of the substance which is deposited in a cold infusion of cocoa. (See page 15.) The Commission of the Lancet' proposes to obtain an estimate of the quantity of starch by the thickness of the clear stratum occurring in a decoction of cocoa when cold; it is, however, evident that such measurements can only be considered approximately correct. The analyst ought first to make the experiment with a known quantity of pure cocoa mixed with a given amount of starch. In the investigations instituted by the Commission of the Lancet,' five tubular glasses each seven inches and a half in height, three fourths of an

inch in diameter, and holding twelve drachms of water, were filled with five different cold decoctions of cocoa, containing respectively 50, 40, 30, 20, and 10 per cent. each of starch; in the first, the thickness of the clear stratum was one inch; in the second, one inch and a half; in the third, two inches; in the fourth, two inches and a half; and in the fifth, two inches. The proportion of the ingredients forming each decoction was 220 grains, by weight, of a mixture of cocoa and potato flour, to eight ounces of water, the boiling being continued for five minutes in each case.

Sugar.-Should the cocoa contain sugar as well as starch this must be first removed by means of cold distilled water, and its amount ascertained. The Commission of the 'Lancet' recommends the following short and practical method of determining the quantity of sugar in cocoa. Dissolve in cold water a weighed quantity of dry cocoa containing sugar; filter, dry the residue by means of blotting-paper and heat, weigh; the loss will indicate very nearly the amount of sugar with which the sample of cocoa operated upon was admixed. Of course this method of analysis supposes that cocoa contains no other principle soluble in water than sugar; this appears to be the case, from the Commission having observed that pure cocoa when immersed in cold water for some minutes, loses only about 3 per cent. of its weight. A rough way of testing the presence of sugar.in the cold extract of cocoa would be to evaporate it nearly to dryness, and taste the few last drops; this experiment can be made at any time on the breakfast table: let a teaspoonful of cocoa be scraped with the knife or crushed with its handle, if in the form of nibs, place it for five minutes in a cup containing a tablespoonful of cold water, and strain through the corner of a napkin into another clean tablespoon; finally, evaporate the fluid by heating

the spoon over a few red hot ashes, or upon a spirit lamp; when only a few drops of it remain in the spoon, ascertain, by tasting, whether the extract be sweet. (See also the article on Alcoholic Beverages.)

Mineral Substances.-The mineral substances employed for the adulteration of cocoa are carbonate of lime or chalk, sulphate of lime or plaster of Paris, red earth, red ochre or Venetian earth, the three latter being chiefly employed to colour the cocoa. To detect these adulterations, the cocoa may be incinerated, and the ashes tested; but I think it will be found preferable to scrape the falsified sample, or crush it into a fine powder; boil it thoroughly with water until nothing more be dissolved from it, and decant the fluid. Let the insoluble residue be now tested for carbonate of lime by pouring dilute hydrochloric acid upon a sample of the undissolved powder, and noticing whether any carbonic acid be evolved (see also page 18); for sulphate of lime, by fusing a sample of the residue with nitrate of potash, dissolving the fused mass in water, and testing this solution with oxalate of ammonia for lime, and with chloride of barium for sulphuric acid (see also page 19); and for red earth, or mineral substances containing iron, by adding an excess of potash to the residue dissolved in hydrochloric acid, when a dirty red precipitate will appear if iron be present, the addition of ammonia and sulphide of ammonium to the solution will give a black precipitate. Ferrocyanide of potassium and nitric acid are sure to yield a blue colour in the acid fluid, iron being always present in vegetable substances, though in minute quantities, so that this test is not available.

III. SAGO

Is the starch from the pith of palms, and is imported from

the Maldives, Sumatra, New Guinea, the Moluccas, &c. Many species of palms are capable of yielding starch; amongst these are Sagus rumphii, Cicas inermis and revoluta, Coryota urens, Borassus gomato, several species of Zamia, Corypha, and Mauritia. The starch is contained in the pith-like substance, which forms the chief bulk of the entire stem, often attaining the thickness of the human. body in seven years. A single stem of this kind is said to yield three hundred-weight of sago. To obtain it, the pith separated from the stem, is washed upon sieves, and the starch collected. The granulation is performed upon sieves in such a manner that the little lumps which pass through the meshes, fall upon a hot plate of copper. Each lump is thus converted into paste, the starch granules immediately swelling up in the hot liquid; these dry into the irregular roundish translucent masses which constitute the sago of

commerce.

A distinction is made between white, red, and gray sago; the red variety being often converted, by the process of manufacture, or by natural change, into the gray modifi

cation.

A considerable quantity of sago is now made from potato starch, in the same manner as that from the palms. It is difficult, however, to communicate the same degree of hardness to potato sago, as is possessed by the foreign product; it has a greater or lesser tendency to become pasty when boiled, which is not the case with the genuine article ; moreover the starch granules of sago (see woodcut, page 15) are ovate, rounded at one extremity, the other being truncated; the hilum is usually surrounded by a distinct ring. This starch or meal is frequently employed in the adulteration of arrow-root.

1 Knapp's 'Chemical Technology,' v. iii, p. 230.

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