Bibliography

1. K. Saito and A. Fukushima, "Effect of External Conditions on the Stability of Enzymatically Synthesized Carthamin," Acta. Soc. Bot. Pol. 55, 639-651 (1986).

2. F. J. Francis, Handbook of Food Colorant Patents, Food and Nutrition Press, Westport, Conn., 1986.

3. K. Saito and A. Fukushima, "On the Mechanism of the Stable Red Colors of Cellulose-bound Carthamin," Food Chem. 29, 161-175 (1988).

4. F. J. Francis, "Less Common Natural Colorants," in G. A. F. Hendry and J. D. Houghton, eds., Natural Food Colorants, 2nd ed., Blackie Academic and Professional, Glasgow, Scotland, 1996, pp. 310-342.

5. F. J. Francis, "Miscellaneous Colorants," in G. A. F. Hendry and J. D. Houghton, eds., Natural Food Colorants, Blackie Academic and Professional, Glasgow, Scotland, 1992, pp. 242-272.

COLORANTS: CHLOROPHYLLS

The chlorophylls are a group of naturally occurring pigments present in all photosynthetic plants including the algae arid some bacteria. They are in greater abundance than any other organic pigment produced in nature. Hendry estimated annual production at about 1,100,000,000 tons as compared with carotenoids at 100,000,000 tons, with about 75% being produced in aquatic, primarily marine, environments (1). Obviously, as a source of raw material for food colorants, supply is no problem.

series of reactions occurs with chlorophyll b. Several other degradative reactions also occur, but the change to pheo-phytin is the major change that occurs when products containing chlorophyll are heated. The trivial names chlorophyll, chlorophyllide, pheophytin, and pheophorbide were developed historically and have been retained even though the chemical nomenclature has been changed by the IUB-IUPAC Joint Commission on Nomenclature in 1980. A good description of the new nomenclature and the chemistry of chlorophylls has been provided by Hendry (1).

The chlorophylls have a bright green color, whereas the pheophytins are olive green; thus, major efforts to maintain the attractive green color in vegetables during processing have been to retain the magnesium in the molecule. Pretreatment and treatment during processing in alkaline solutions containing magnesium (the Blair Process) were successful in retaining the green color for a short time after thermal processing. Enzymatic treatments to convert the chlorophyll to chlorophyllide were attempted because the chlorophyllides have a color similar to the chlorophylls and are more stable, and they did help to maintain the color. A combination of the two processes with high-temperature short-time (HTST) processing also maintained the color a little longer. But the overall effect was that the retention of attractive color was only a few weeks and not long enough to provide an economic incentive, so the attempts were abandoned. The same problems with stability were experienced with attempts to make colorants containing chlorophyll.

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