Plant Pigments: An Eco-friendly Alternative to Artificial Food Dyes

MD Abdur Rahim PhD

Md. Abdur Rahim, PhD

Colors are an essential part of our daily lives, as we need them for food, clothes, and shelter.

They are the key factors that determine the consumers’ preference and acceptance/rejection of foods. Since the beginning of time, food has been flavored to improve its look, flavor, and appeal, as well as to make it easier for customers to identify it when they see it. In addition, colors serve as visual cues that food is deteriorating. There are two types of colors used in food coloring: artificial and natural. Artificial colorants, on the one hand, are compounds that

are produced through chemical reactions and are not found in nature. In 1856, a British chemist, William Henry Perkin, discovered the first artificial organic dye, ‘purplish lilac’ from coal tar. The commonly used artificial food colorants are allura red, sunset yellow, amaranth, brilliant blue, tartrazine, erythosine, quinoline yellow, indigo carmine, brown FK and brown HT, green S, patent blue V, lake colorants, etc. On the other hand, natural food colorants are coloring agents that are present in naturally edible sources. Plants are the primary source of natural food coloring, which is used in human nutrition. For example, chlorophylls, carotenoids, betalains, and anthocyanins are the most common natural food

colorants.

Chlorophylls are the furthermost available natural pigments found in all green plants, algae, and photosynthetic bacteria. They are valuable to human health; they act as chemotherapeutic agents and reduce the carcinogenic effect of heterocyclic amines, which usually form when we cook meat or fish at high temperatures. These natural green pigments are used as food colorants and in the pharmaceutical and cosmetic industries. Usually, chlorophyll colorants

are extracted from various photosynthetic plants, including alfalfa, nettles, spinach, and other edible plants. Furthermore, a considerable amount of chlorophyll has been extracted from the blue-green algae spirulina. However, chlorophyll colorants are unstable and change to brown, while the addition of copper to the chlorophyll molecule stabilizes the structure and doesn’t change the green color. The copper-inserted chlorophyll colorants are designated as the food additive code ‘E141’ in the European Union and ‘73.125’ of the U.S. Food and Drug Administration (FDA). A variety of dairy products, candies, jams, jellies, and baked goods use green chlorophyll colorants.

Carotenoids are lipid-soluble pigments found in both plants and animals and produce yellow, orange, and red colors. Only plant-derived carotenoids are used as food colorants.

Carotenoids are responsible for the colors of many flowers, fruits, and seeds. Carotenoid pigments are extracted from different plant parts; for example, yellow affron colorant is isolated from the dried stigma of saffron crocus flowers and used in the food, pharmaceutical, and cosmetic industries. Orange-colored carotenes derived from edible plants, like carrots, oil palm fruits, and other plant sources, are used as a natural food colorant. The red-colored lycopene is found in tomatoes, watermelon, and pink grapefruits. Tomatoes are the best source of lycopene as a natural food colorant. Besides being used as a food colorant, carotenoids are beneficial to human health as they are decreasing the risk of various chronic diseases, specifically certain cancers and eye disorders. Betalains are the water-soluble natural pigments extracted from the roots of red beet. These pigments come in two forms: reddish-purple betacyanins and yellow colored betaxanthins.

The most predominant source of betalains is red beet. The other sources of betalains are ripened red-violet fruits of spinach (pui shak), globe amaranth (botam phul), dragon fruits, Swiss chard (a green leafy vegetable), ullucus (a root crop grown in Andean states of South America), etc. Betalains are also valuable to human health as they act as anti-inflammatory, anti-diabetic, antioxidant, and anti-cancer agents. The betalains with pink or violet colors extracted from red beet roots are designated as the food additive code ‘E162’ in the European

Union and ‘73.40’ of the FDA. beetroot betalains are commonly used as food colorants in yogurts, ice creams, chewing gums, sauces, soups, etc. Moreover, this pigment is used as ingredients in cosmetic and pharmaceutical industries.

Anthocyanin pigments are water-soluble bioactive compounds found only in plants. Plants don’t contain two pigments, batalains and anthocyanins, together in the same species/different species of the same family. Anthocyanins are the key determinant of colors of different plant parts like leaf, stem, root, flower, fruit, as well as seed. They differ in colors from red, purple, and black to blue depending on the pH of the cell vacuole. These pigments possess antioxidant activity since they have free radical scavenging properties and protect humans from cancer, cardiovascular diseases, diabetes, neurodegenerative, and age-related diseases. Anthocyanins isolated from edible plants also possess medicinal properties. In addition, in 2001, a Norwegian company ‘Biolink Group’ launched the first anthocyanin pills as natural dietary supplements from bilberry and blackcurrant, which were further approved by the FDA during 2007. Currently, anthocyanin food colorants are extracted from grape, bilberry, blueberry, red cabbage, and blackcurrant, which are used in various foods, including

soft drinks, desserts, ice cream, and dairy products. The anthocyanin natural colorants are designated as the food additive code ‘E163’ in the European Union.

There are some complaints that some dishonest food caterers use non-food-grade chemical colorants like harmful textile dye instead of food-grade colorants to color foodstuffs like sweetmeats, ice cream, jilapi, beguni, butter, chewing gum, candy, chips, hen egg, biriyani, etc., which is a threat to human health. These food color adulterations can cause chronic health hazards, including cancer. In the food industry, colorants are regularly used to produce soft drinks, bakery items, canned items, dairy items, and meat and fish products. Therefore,

government authorities like BSTI should take proper initiative to ensure the use of food-grade colorants within the limits instead of synthetic, low-quality non-food-grade colorants by the food caterers/manufacturers, and to fulfil this, proper legislation should be ensured.

Moreover, they can create awareness among food caterers and manufacturers about the health benefits of plant-derived natural colorants. Considering the health benefits and nutritional properties, it can be said that plant-based natural colorants could be a better replacement for synthetic colorants in foods. Finally, the government should encourage and patronize the producers of natural colorants in Bangladesh.

(The author is a anthocyanins researcher and Professor, Department of Genetics and Plant Breeding at Sher-e-Bangla Agricultural University, Dhaka)