This section is from the book "A Treatise On Beverages or The Complete Practical Bottler", by Charles Herman Sulz. Also available from Amazon: A Treatise On Beverages.
Of the various red colorings only a limited number is valuable for the bottlers' purpose viz.: cudbear, cochineal and its deri-vate carmine, besides aniline red. All other red colorings, such as car-tharmin, alkanine, alloxan and other vegetable colorings, are practically valueless to the bottler.
The cochineal is a little insect which feeds upon the cactus plant, and is found in warm climates, and 49 is especially cultivated for this purpose in most of the Central American States. The dried body of the insect yields a magnificent red coloring matter. Its use is harmless, and is extensively employed, not only in dyeing, but for coloring drinks of various kinds, and confectionery. There are two varieties known in commerce - silver cochineal, which has a purplish-gray or silver-gray color; and black cochineal, which is smaller, and of a reddish or purplish-black color. The former is that commonly met with. Commercial cochineal is frequently increased in weight by metals, such as lead, iron oxides, barium, talcum and similar substances. These adulterations are effected by exposing the cochineal to steam until the insects have attained their normal size without becoming wet, adding the powder, rotating the mixture in a drum, and finally drying by heat, when the adulterant will adhere between the wrinkles. Other and similar frauds are committed, but readily detected by macerating some of the insects in water, when the powder is soaked off, and the insect may be examined.
Factitious cochineal is made of gums, starch and various coloring and mineral matters, and sometimes met with in the trade.
The coloring principle of cochineal is chemically known as carminic acid, technically called "carmine," which is unalterable in dry air, is very soluble in water, soluble in cold, and more so in boiling alcohol, insoluble in ether and without nitrogen. The watery infusion of cochineal is of a violet-crimson color, which is brightened by the acids and deepened by the alkalies. The coloring matter is readily precipitated. Its alcoholic solution is precipitated by alkalies, but the crimson color of its aqueous solution is succeeded by a purplish-red, and precipitated on the addition of alkaline earths.
Various cochineal colorings are prepared as follows: Take three and one-half ounces of best cochineal, bruised; one drachm tartaric acid, powdered; one and one-half drachms of cream of tartar, powdered; pour on it two pints of boiling water, let the whole rest for twenty-four hours. Then filter and neutralize the filtrate cautiously with about two drachms acetic acid, or boil two ounces of bruised cochineal with one drachm of cream of tartar, and filter. Test these solutions with litmus paper, whether they are neutral or not, and if necessary neutralize cautiously "with acetic acid.
A good tincture of cochineal is prepared by using two ounces of cochineal to about one-half drachm of soda. Bruise the cochineal with the soda, and put the powder on a paper filter. Then pour about four pints of diluted alcohol into it.
A bottler without an intelligent conception of the process and familiarity with this preparation is advised not to attempt to prepare the cochineal coloring, as he can obtain it to much better advantage from his supplier. If the color is not properly prepared it produces no brilliant red. The color of carmine is more easily prepared. If the batch of cochineal coloring should fade in the beverage, be sure that some sulphuric acid from the generator has come over to the fountain by carelessness, or that the water was not thoroughly purified.
Carmine is the coloring principle of the cochineal, extracted from the latter by boiling and precipitated with alum, or extracted with a solution of carbonate of soda and precipitated with diluted acids. Its preparation requires a great deal of experience, and depends much on circumstances, and should therefore never be tried in the bottlers' laboratory, since commercial carmine is to be had at reasonable figures, and in all degrees of purity. In commerce the various grades are designated by numbers, the highest number, generally No. 40 - in some price lists, No. 60 - means the best, and this always should be used, as it gives a stronger and more brilliant red than the rest. Carmine is classed with the vegetable colors, is not deleterious to health and can be safely used.
A practical process not open to the objections previously mentioned, whereby a more stable, concentrated and thoroughly representative product can be secured, is obtained in the following manner: Take carmine (No. 40), water of ammonia, glycerine in certain proportions, and a sufficient quantity of water. Rub the carmine (one ounce) into a fine powder, with a little water, in a wedge-wood mortar; make a paste with and dissolve in the water of ammonia (one pint of water with one ounce of spirits of ammonia), and then add with constant trituration four ounces of glycerine. Transfer to a porcelain capsule, and heat upon a water-bath, until the liquid is entirely destitute of ammoniacal odor; when sufficiently cool, bottle and cork. The entire removal of the ammonia gas, requires the constant stirring of the liquid with a glass rod, and rather lengthy heating. By boiling the volatile ammonia evaporates. The ammonia can also be neutralized by the addition of a few drops of acetic acid, but care must be taken and the neutralization ascertained with litmus paper, which should retain its blue color, otherwise some more ammonia or acetic acid has to be added for correction.
The finished product is a permanent, deep, ruby-red liquid, perfectly transparent, destitute of ammoniacal odor, and mixes, without turbidity, with all aqueous solutions. The depth of color or strength of tincture may be varied to suit individual tastes. If the carmine does not entirely dissolve, add a little more ammonia, and should this be of no service, it proves that the carmine is adulterated. Carmine coloring does not stain or tarnish the bottles.
If the batch of carmine coloring should fade, be sure that sulphuric acid or sulphuric vapors have come over from the generator to the fountain by careless charging.
The water of the beverages must have been previously well purified, as many spring or well waters show against cochineal and carmine tinctures an alkaline reaction.