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"Green" extraction method to produce red pigment

Plant-derived pigments are an important source of non-toxic compounds used as coloring agents for food products or cosmetics. In addition to their known nutritional value, the red pigments found in hot pepper (chili) are important as a source of non-toxic red coloring agents; The red pigments are added to many processed food products as well as cosmetic products in order to increase their color. Extracts can be prepared from different varieties of the pepper in order to isolate the natural red pigment, which can replace the dangerous synthetic dyes.

student with carotenoids. Image: Rich Richins. Photo: University of New Mexico
student with carotenoids. Image: Rich Richins. Photo: University of New Mexico

Until today, the common method for extracting red pigments from dried red pepper fruits required the use of hexane as the extraction solvent. The findings of a new study conducted at the University of New Mexico describe an effective extraction process of these important red pigments through "green chemistry". With the help of the new method, the researchers were able to extract 85% of the desired pigments (of the carotenoid type, The term on Wikipedia) from dried pepper and reduce the hazardous waste and risks to the environment associated with normal extraction methods.

In the state of New Mexico, the economic value of the hot red pepper crop - chili - includes the fruit collected in its green form as well as the dried red fruit form that is usually collected later in the season. Current extraction processes are limited; Red pigment can only be extracted from varieties of American paprika or from other cultivated varieties.

According to a research team from the Department of Plant and Environmental Sciences at the University of New Mexico, if it is possible to extract red pigments separately from the substances called capsaicinoids (capsaicinoids, The term on Wikipedia) then it will be possible to use a wider variety of red cultivated plants, including those with important values ​​such as fresh crops.

The researchers developed a "green" (environmentally friendly) chemical method for obtaining a fatty substance (oleoresin) from dried red pepper fruits that has the same composition of the essential substances (carotene, xanthophyll) obtained by the hexane-based extraction method.

One of the researchers explains: "It will be possible to develop "green" extraction methods that will replace the use of hexane as a solvent for the production of oleoresin. This ability will reduce the environmental risks in the isolation of red pigments from red pepper."

The "green" extraction method includes a process in which the pigments are separated from the capsaicinoids - an important step, which, according to the researchers, increases the flexibility of the process so that a variety of varieties of red peppers can be used for the production of pigments.

The researchers explain that the type of new method - extraction using a supercritical fluid - presents an advantage, relative to a collection of red fruits mixed with green materials derived from leaves, since this method reduces the amount of chlorophyll, a substance that contaminates the pigment extract, compared to extraction in hexane.

The news about the study

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