Natural Pigments as Food Colorants

Delgado-Vargas, F. and Paredes-Lopez, O., Pigments as food colorants, in Natural Colorants for Food and Nutraceutical Uses, CRC Press, Boca Raton, 2003, chap. 4. 

The documented use of betalain pigments as food colorants dates back at least one century, when inferior red wines were colored with betalain-containing juices (e.g., red beet juice). This common practice was, however, soon prohibited, and the application of betalain colorants was widely replaced by artificial dyes, which displayed better stability, at a lower price, and with higher purity. But in recent years the interest in natural food colorants has been renewed, mainly because of consumers concerns about the safety of some artificial colorants, which may be hazardous to human health (234). As a result, the number of permitted artificial dyes has been markedly reduced, and new efforts had to be made to develop natural food colorants (235). However, current legislation restricts the application of betalain colorants to concentrates or powders (E 162) obtained from aqueous extracts of beets (211). 

Von Elbe, J.H., Stability of betalaines as food colors, Food TechnoL, 29, 42, 1975. Kimler, L. et al., Betalamic acid, a new naturally occurring pigment, J. Chem. Soc./Chem. Commun., 21, 1329, 1971. 

Studies of the stability and stabilization of anthocyanins are still required, based on the extreme importance of those pigments for food colors. Modem HPLC-MS equipment also allows us to easily follow the copigmentation reactions in detail, calculate their kinetic and thermodynamic parameters, identify the products formed during the reactions, and thus shed new light on the stability and stabilization of these pigments. Since anthocyanins play important roles as natural colorants for... 

In recent decades, the synthetic colorant market has dechned, to the benefit of the natural-oriented market and consumers. Excluding FD C Red 40 and Red 28, the synthetic colorants are now as well accepted as they were. In addition to the decreasing enthusiasm for chemicals in food, the high costs of toxicological studies also inhibit the development and approval of new synthetic colorants. The existing technologies used for the extraction, concentration, and purification of natural plant pigments to be used as food colorants still produce lower yields and the final products are still expensive. 

The chemical structure of some typical carotenoids is shown in Fig. 8.2. Beta-carotene occurs in nature usually associated with a number of chemically closely related pigments and extracts have been used as food colorants for many years. For example, palm oil has a high concentration of carotenoid pigments, primarily beta-carotene and about 20 others. Cmde palm oil has been used extensively as a cooking oil because of its desirable flavor and as a general... 

Caramel colors are brown pigments produced by reaction of a saccharide with a browning accelerator. They can be considered a natural material as caramels may be formed in food. Caramels are prepared as food colors by heating a solution of a sugar (commonly glucose or sucrose) with the accelerator. The caramels can be classified as one of four types [1] shown in Table 11.1.1. 

Carotenoids (Figure 2.8) are yellow orange and red terpenoid pigments in microalgae. The two main compounds are -carotene and astaxanthin. Carotenoids are mosdy used as food colorants and supplements for human and animal feeds. Both -carotene and astaxanthin can be synthesized through chemical reactions at a much lower price compared with those derived from microalgae. However, natural carotenoids have the... 

Titanium dioxide (E171, Cl white 6) is a white, opaque mineral occurring naturally in three main forms rutile, anatase, and brookite. More than 4 million tons of titanium dioxide are produced per year and it is widely used for industrial applications (paints, inks, plastics, textiles) and in small amounts as a food colorant. ° "° Production and properties — Titanium oxide is mainly produced from ilmenite, a titaniferous ore (FeTiOj). Rutile and anatase are relatively pure titanium dioxide (Ti02) forms. Titanium oxide pigment is produced via chloride or sulfate processes via the treatment of the titanium oxide ore with chlorine gas or sulfuric acid, followed by a series of purification steps. High-purity anatase is preferred for utilization in the food industry. It may be coated with small amounts of alumina or silica to improve technological properties. 

Although chlorophyll and chlorophyllin colorants seem to be easily obtained, in practice their production as natural food colorants is rather difficult. The sensitivity of chlorophylls to certain enzymes, heat, and low pH, and their low tinctorial strength greatly limit their manufacture and application as food additives, principally when the pigments are isolated from the protective environment of the chloroplasts. The well-known instability of chlorophylls prompted extensive research for developing... 

Mapari, S.A.A. et ah. Exploring fungal biodiversity for the production of water-soluble pigments as potential natural food colorants, Curr. Opin. Biotechnol, 16, 231, 2005. 

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