Oh O

3/CH3

OH O OH Alkannet

3/CH3

Ceroalbolinic acid

OH O OH Alkannet

Figure 1. Structures of some anthraquinones.

compound. More recently, purification methods including proteinase enzyme treatments have produced colorants sometimes known as the "carmines of cochineal." The word carmine has been used a general term for this class of anthraquinones, but the more usual meaning of the term carmine (CAS Reg. No. 1390-65-4) denotes a magnesium or aluminum lake of carminic acid. Carminic acid (Fig. 1) is the pigment in cochineal, and the lakes usually contain about 50% of carminic acid. The content of carminic acid is usually the way of specifying the strength, but Schul (1) suggested that the price of carmine should be based on its color strength, not on the carminic acid content, and provided details of a method. The FDA-approved procedures are specified in the CFR Section 73.100 for Carmine.

Solutions of carminic acid at pH 4 show a pale yellow color and actually have little intrinsic color at pH values below 7, but they do complex with metals to produce stable brilliant red hues. Complexes with tin and aluminum produce the most desirable hues, and nearly all commercial preparations contain aluminum. A range of hues from "strawberry" to "black currant" can be produced by adjusting the ratio of carminic acid to aluminum. The color is essentially independent of the pH value, being red at pH 4 and bluish-red at pH 10. Aluminum lakes are soluble in alkaline media and insoluble in acids. Carmine is very stable to heat and light, resistant to oxidation, and not affected by sulfur dioxide. The presence of other metal ions may shift the color slightly toward the blue.

Carminic acid is usually available as an aqueous solution with a colorant content about 2 to 5%. It may also be spray-dried. Formulations may also contain propylene glycol citric acid, and sodium citrate. Carmine is usually supplied as an alkaline solution with a carminic acid content of 2 to 7%. Traditionally, ammonia was used as an alkan-izing agent, but recently formulations with potassium hydroxide, spray-dried with maltodextrin as a carrier, have become available. They may also contain sodium hydroxide, ammonium hydroxide, and glycerol. The intensity of carmine lakes is almost twice that of carminic acid; thus, they are more cost-effective as colorants.

Applications

Carmine is considered to be technologically a very good food colorant. Its only significant limitation is with products at low pH values. It is ideally suited for comminuted meat products such a sausages, processed poultry products, surimi, and red marinades. Other important uses are in jams and preserves, gelatin desserts, baked goods, confections, icings, toppings, dairy products and soft drinks. The level of usage varies with the product and is usually 0.05 to 1.0%. Cochineal and carmine are permitted as food colorants in the United States.

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