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Anthocyanins as food colors
Fd Chem. Toxic. Vol. 21, no. 4, pp. 509 514, 1983 Printed in Great Britain
0015-6264/83503.00 + 0.00 Pergamon Press Ltd
Review Section REVIEWS OF R E C E N T P U B L I C A T I O N S
Anthocyanins as Food Colors. Edited by P. Markakis. Academic Press Inc., London, 1982. pp. xii + 263. £23.20.
Anthocyanins are responsible for much of the blue, purple and red coloration of flowers, berries and other parts of plants and, as the principal pigments of many ripe edible fruits, they not only act as indicators of quality but have featured consistently in most human diets. Because of their natural occurrence in many foods, backed to some extent by their reported metabolism by the intestinal flora to carbon dioxide and various aromatic acids, they are thought to have potential as replacements for listed artificial food colourings. However, a few years ago JECFA (21st meeting; Tech. Rep. Ser. Wld Hlth Org. 1977, 617, 15) noted the absence of any toxicological data on the isolated anthocyanins and did not establish an ADI. Moreover, although the water solubility of the anthocyanins aids their incorporation into aqueous food systems, their colouring capacity and stability in foods are generally inferior to those of the coal-tar dyes. These and other aspects of anthocyanins relevant to the processing of foods containing them and to their potential use as food additives feature in the volume named above. The first half of the book deals with the chemistry of anthocyanins, their interaction to form pigments and their biosynthesis, and describes the occurrence, structure and reactions of the proanthocyanidins, the flavonoid precursors responsible, for example, for the development of cloudiness in beer and the browning of the cut surface of an apple. A review of the distribution of anthocyanins among food plants demonstrates their widespread occurrence in the edible tissues. A consideration of the factors responsible for the well-recognized instability of these compounds, both in living plant tissues and in plant products, ranges from physical factors (temperature, light and pH) to enzymes, oxygen, ascorbic acid, sugars, sulphur dioxide, metals and condensation reactions. This is followed by a review of analytical methods for anthocyanins, including quantitative procedures suitable for different types of food product. An interesting contribution on the anthocyanins of grapes and wines points out that the basic distinction between red and white wines stems from the use of grapes with a genetically determined ability or inability to synthesize anthocyanins. In the former case, the type of anthocyanin glucoside synthesized by a given red grape is another permanent genetic character, which can be used to distinguish between wines made from different species of vine. Recent studies have been concerned with possible correlations between these compounds and the overall quality of a wine.
The economic, technological and legal aspects of using anthocyanins to colour foods and of producing the colourings by processing suitably coloured plant materials are touched upon in the final chapter. The chemical synthesis of anthocyanins is said to be complex and uneconomic. Their isolation by the processing of natural products is less so, but would probably be viable only if waste products or byproducts of the processing of important crops, or alternatively plant materials of no economic importance, were used as the raw material. Like the synthetic materials, anthocyanins produced by the processing of natural substances would have to be subjected to toxicological testing before being marketed as tbod additives, although no such testing is required when intensely pigmented fruit juices or fruit juice concentrates are used to colour foods. Taken as a whole the book provides an interesting and helpful survey of a class of natural compounds that may in time become more important to industry. IARC Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans. Vol. 25. Wood, Leather and Some Associated Industries. pp. 412. Sw. fr. 60.00 (1981). Vol. 28. The Rubber Industry. pp. 486. Sw.fr. 70.00 0982). International Agency for Research on Cancer, Lyon (available in the UK through HMSO).
Publication of these two volumes reflects the expansion of the IARC programme to include consideration of human exposures to complex mixtures of chemicals in selected occupations. In each case the Working Group has attempted to describe the known human exposures to exogenous and endogenous chemicals involved in the processing or use of materials in the industry and has reviewed the relevant epidemiological and experimental data. The industries were chosen for examination on the basis that there exist epidemiological data suggesting that they may carry an increased risk of cancer. The complex mixtures of chemicals investigated within these industries were selected because of evidence of human exposure and the existence of data linking that exposure with cancer in man. Many difficulties were encountered by the Working Groups evaluating the carcinogenic risks, not least in the assessment of the human exposures associated with various processes, the interpretation of job titles, differing technologies used within the same industry and evolution of the industries with time. The evaluations were further complicated by the complex nature of the materials being considered. Moreover, in addition to the recognized limitations of epi509
0015-6264/83503.00 + 0.00 Pergamon Press Ltd
Review Section REVIEWS OF R E C E N T P U B L I C A T I O N S
Anthocyanins as Food Colors. Edited by P. Markakis. Academic Press Inc., London, 1982. pp. xii + 263. £23.20.
Anthocyanins are responsible for much of the blue, purple and red coloration of flowers, berries and other parts of plants and, as the principal pigments of many ripe edible fruits, they not only act as indicators of quality but have featured consistently in most human diets. Because of their natural occurrence in many foods, backed to some extent by their reported metabolism by the intestinal flora to carbon dioxide and various aromatic acids, they are thought to have potential as replacements for listed artificial food colourings. However, a few years ago JECFA (21st meeting; Tech. Rep. Ser. Wld Hlth Org. 1977, 617, 15) noted the absence of any toxicological data on the isolated anthocyanins and did not establish an ADI. Moreover, although the water solubility of the anthocyanins aids their incorporation into aqueous food systems, their colouring capacity and stability in foods are generally inferior to those of the coal-tar dyes. These and other aspects of anthocyanins relevant to the processing of foods containing them and to their potential use as food additives feature in the volume named above. The first half of the book deals with the chemistry of anthocyanins, their interaction to form pigments and their biosynthesis, and describes the occurrence, structure and reactions of the proanthocyanidins, the flavonoid precursors responsible, for example, for the development of cloudiness in beer and the browning of the cut surface of an apple. A review of the distribution of anthocyanins among food plants demonstrates their widespread occurrence in the edible tissues. A consideration of the factors responsible for the well-recognized instability of these compounds, both in living plant tissues and in plant products, ranges from physical factors (temperature, light and pH) to enzymes, oxygen, ascorbic acid, sugars, sulphur dioxide, metals and condensation reactions. This is followed by a review of analytical methods for anthocyanins, including quantitative procedures suitable for different types of food product. An interesting contribution on the anthocyanins of grapes and wines points out that the basic distinction between red and white wines stems from the use of grapes with a genetically determined ability or inability to synthesize anthocyanins. In the former case, the type of anthocyanin glucoside synthesized by a given red grape is another permanent genetic character, which can be used to distinguish between wines made from different species of vine. Recent studies have been concerned with possible correlations between these compounds and the overall quality of a wine.
The economic, technological and legal aspects of using anthocyanins to colour foods and of producing the colourings by processing suitably coloured plant materials are touched upon in the final chapter. The chemical synthesis of anthocyanins is said to be complex and uneconomic. Their isolation by the processing of natural products is less so, but would probably be viable only if waste products or byproducts of the processing of important crops, or alternatively plant materials of no economic importance, were used as the raw material. Like the synthetic materials, anthocyanins produced by the processing of natural substances would have to be subjected to toxicological testing before being marketed as tbod additives, although no such testing is required when intensely pigmented fruit juices or fruit juice concentrates are used to colour foods. Taken as a whole the book provides an interesting and helpful survey of a class of natural compounds that may in time become more important to industry. IARC Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans. Vol. 25. Wood, Leather and Some Associated Industries. pp. 412. Sw. fr. 60.00 (1981). Vol. 28. The Rubber Industry. pp. 486. Sw.fr. 70.00 0982). International Agency for Research on Cancer, Lyon (available in the UK through HMSO).
Publication of these two volumes reflects the expansion of the IARC programme to include consideration of human exposures to complex mixtures of chemicals in selected occupations. In each case the Working Group has attempted to describe the known human exposures to exogenous and endogenous chemicals involved in the processing or use of materials in the industry and has reviewed the relevant epidemiological and experimental data. The industries were chosen for examination on the basis that there exist epidemiological data suggesting that they may carry an increased risk of cancer. The complex mixtures of chemicals investigated within these industries were selected because of evidence of human exposure and the existence of data linking that exposure with cancer in man. Many difficulties were encountered by the Working Groups evaluating the carcinogenic risks, not least in the assessment of the human exposures associated with various processes, the interpretation of job titles, differing technologies used within the same industry and evolution of the industries with time. The evaluations were further complicated by the complex nature of the materials being considered. Moreover, in addition to the recognized limitations of epi509