Natural edible dye preparation from bean husks giving red shades

Details Natural edible dye preparation from bean husks giving red shades Natural edible dye preparation from bean husks giving red shades

1982-02-19

1983-05-17

Clingman, A. Lionel

Bleaching and dyeing; fluid treatment and chemical modification

Process of extracting or purifying of natural dye

8436, 8499, 8919, 426 46, C09B 6100

Patent

active

043838332

DESCRIPTION:

BRIEF SUMMARY
At the present time, synthetic dyes are predominantly used for foodstuffs, snack foods, beverages, and pharmaceutical and cosmetic products. Since some of these dyes are physiologically objectionable and since the consumer has become more aware of the environment, the trend is toward using natural dyes. This trend is reinforced by laws and legal opinion in the field of foodstuff law in all the countries of the world.
Where natural dyes from flowers or fruits, such as hibiscus flowers or elderberries, are already being used for products such as those named above, the dyes are obtained by extraction methods and have the disadvantage that they are not sufficiently stable under the effect of heat and light and that they can be standardized only with great difficulty.
Surprisingly, it has now been discovered that the dye in the infrared and ultraviolet spectra shown in FIGS. 1 and 2 respectively and obtainable from natural raw materials eliminates the above disadvantages. Experiments have shown that products treated with this dye exhibit no changes in color at all, even after being stored in daylight and at room temperature for one year. Even higher temperatures such as those in the tropics do not affect the color quality. When diluted to the extent which is normal in this field, the dye is a strong red, and colorings from pink to deep dark-bluish red can be attained with this dye, depending on the concentration, as shown in the following table:


TABLE 1



Coloration of 0.1% solutions of the dye in H.sub.2 O (dye extracted with
citric acid)
pH 1.0: attractive, strong red without lavender tinge (acidulated with HCl)
After being made alkaline and then reacidulated, the color intensity fades and changes to orange (pH 4.0).
A 10% dye solution is a pronounced eggplant color (pH 5.5).
For dyeing purposes in the field of foodstuffs, the following concentrations are suitable:
pale pink: 0.05% solution, pH 4.5
strong red: 0.35% solution, pH 4.5
deep red: 0.55% solution, pH 4.5
A solution concentrated to 50 Brix and then spray-dried produces a powder of almost black-violet color.
It is worthy of mention that the dye solution can also be concentrated at normal atmospheric pressure and 100.degree. C., without destroying the dye.
The method for producing the dye begins with colored beans of the genus Phaseolus, especially the black-colored cultivated forms of common beans (Phaseolus vulgaris), which are one of the basic foods of the indigenous population in South America. This raw material is substantially less expensive than other natural dye sources or the raw material for synthetic dyes. The skins of all the colored varieties of the genus, Phaseolus, can be used as raw material. Besides the Phaseolus vulgaris already mentioned, scarlet runner beans (Phaseolus coccineus) and Phaseolus caracalla could be especially named.
The method includes the following basic steps:
(a) The skins of the above-noted black beans, either uncooked or efficaciously briefly soaked, or a powder of these skins is boiled for some time with enough slightly acidic water, preferably the aqueous solution of a hydroxycarboxylic acid, so that an easily stirrable suspension results. After 10 to 15 minutes' boiling, the pH value should be at approximately 5 to 5.5.
(b) After being cooled to the temperature which is efficacious for the following method step, the cell walls of the bean skins are at least partially destroyed in order to release the dye. The cell wall destruction is effected in a manner known per se by enzymatic decomposition, grinding at low temperatures, possibly with the addition of dry ice and/or fine aluminum oxide, or by autoclaving under elevated pressure and increased temperature, or by high-pressure extraction with super-critical gases such as CO.sub.2, or by liquid-liquid extraction with suitable solvents, such as methanol.
(c) The resultant suspension is again brought to a pH value of approximately 4 to 4.5 by adding some acid as required. It is then advantageous to boil up the suspension, which is appropriate in any event in e

REFERENCES:
patent: 4156077 (1979-05-01), Pifferi
patent: 4204043 (1980-05-01), Schultz
patent: 4331765 (1982-05-01), Sakaguchi
patent: 4333955 (1982-06-01), Murata et al.

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