What Is the Use of Natural Food Coloring?

Colorings are inextricably linked to food. They give food an attractive color, which in turn gives consumers a good sensory quality and a strong desire to buy [1]. Natural coloring can be divided into two main categories according to their source: natural and artificial pigments. Natural food coloring is a natural coloring substance obtained by physical extraction and purification from plant, microbial and animal materials. These plant, microbial and animal materials are generally safe and edible [3]. Natural pigments are used as food additives, which are not only relatively safe, but also have important physiological significance for the growth and development of humans, animals and plants. Therefore, the research, development and application of natural pigments have become a hot topic in recent years [5]. This paper discusses natural food coloring from the aspects of the current research status, safety considerations and development trends of natural food coloring.

1 Current application status of natural food coloring

In recent years, China's food coloring industry has grown with the vigorous development of the food industry. The state has proposed the development policy of “natural, nutritious and multifunctional” for food additives according to the needs of the development of the food industry. The priority use of natural coloring in food is advocated, which not only plays a coloring role, but also gives the food certain physiological functions [11]. After more than 20 years of development, the state has gradually standardized and improved the regulatory management of the development, production and use of food additives [4]. In addition to strict hygiene and quality management of existing food colorant products, there are also strict requirements for the approval process of new products, such as the species name of raw materials, source of raw materials, parts to be used, purity of coloring ingredients, ash content, solvent residue, heavy metal residue, total number of colonies, pathogenic bacteria, toxicological experiments and safety levels, stability experiments, product usage methods and effects, etc., all of which are strictly regulated. At present, 47 types of natural coloring have been approved for use in China, which is the most in the world [9].

The proportion of food colorants in food is very small, generally a few thousandths, ten thousandths or even hundred thousandths of the product (drinks, alcohol, pastries, candy, medicine, etc.). However, its role in the product and the scope of its application in food is unmatched by any other food additive [8]. In 2004, the total production and sales volume of natural food coloring was approximately 210,130 tons. The vast majority of products were used domestically, and 17 varieties of natural food coloring were exported, with an export value of approximately 280 million yuan.

Compared with synthetic coloring, the biggest advantage of natural coloring is its relatively high safety. It can better imitate the color of natural substances, and the coloring hue is more natural. In addition, some natural colorings themselves have nutritional value and also have certain pharmacological effects. Therefore, natural coloring has developed extremely rapidly in recent years. The world natural coloring market is growing rapidly at twice the rate of synthetic coloring, and natural coloring replacing synthetic coloring has become a major trend in the development of the coloring industry [10].

1.1 Lycopene

1.1.1 Properties of lycopene

Lycopene is a carotenoid. Because it does not have a ring at the end, it cannot be broken down into vitamin A and is not a source of vitamin A. Lycopene is a fat-soluble pigment that is red in color. It is insoluble in strongly polar solvents such as water, slightly soluble in methanol and ethanol, soluble in ether, petroleum ether, hexane, acetone, and easily soluble in organic solvents such as chloroform, carbon disulfide, and benzene and other organic solvents [13].

1.1.2 Functional properties of lycopene

Lycopene is known as the gold of tomatoes and has a variety of physiological functions: ① Lycopene is a very good antioxidant that can effectively quench singlet oxygen and remove free radicals in the human body, and has a strong effect of reducing oxidative damage to tissues. ② It has anticancer, anti-carcinogenic and antimutagenic effects, and can effectively prevent tumors such as prostate cancer, uterine cancer and lung cancer. ③ Activates immune cells and improves the body's immune system. ④ Prevents cardiovascular and cerebrovascular diseases. The amount of lycopene in the human body is related to human lifespan. Recent studies have shown that lycopene can treat male infertility [11].

Clinical controlled trials conducted by German doctors have shown that middle-aged and elderly men who regularly eat foods containing lycopene can reduce the incidence of prostate cancer by 80%. Middle-aged and elderly women who regularly eat foods containing lycopene can prevent osteoporosis, breast cancer and several other diseases related to aging.

1.1.3 Lycopene research trends

In addition to economically viable extraction methods, the specific physiological functions and changes during processing of lycopene are still waiting to be further studied and discussed. Meanwhile, tomato breeding research aimed at increasing the lycopene content in tomatoes is being carried out from two aspects: conventional and genetic breeding [12]. It has been reported that the lycopene gene has been successfully transferred to Escherichia coli and expressed [11].

1.2 Carotene

1.2.1 Properties of carotene

Extracted from red-fleshed carrots, carotene is a purplish red powder that dissolves in water. Carotene can be converted into vitamin A in the human body, and can be used to enhance the flavor and nutrition of food. It can be used to color beverages, prepared wines, canned foods, candied foods, oily foods or foods such as margarine and shortening. It can also be used to color pasta. It is highly safe and has a balanced coloring power. The amount used is added according to normal production needs [18].

1.2.2 Carrot pigment physiological functions

Studies have shown that the main physiological functions of β-carotene are: (1) Antioxidant function. Carotene is a good antioxidant that can quench singlet oxygen and remove harmful substances produced during physiological metabolism in the human body, such as free radicals that cause tissue damage, cell aging and other lesions. It also has an inhibitory effect on lipid peroxidation. It can prevent light damage to the retina. ②Health function: carotene is a precursor of vitamin A, which is an essential micronutrient for the human body. Used for food fortification to prevent vitamin A deficiency and dry eye disease. ③Immune function: can improve the body's immunity. ④Can prevent cancer and delay its development.

⑤It can promote communication between cells through gap junctions (gapjunction, GJ). Gap junctions are an important form of intercellular communication that allow ions or small molecules with a molecular weight of 1000 Da–1600 Da to pass through, thereby ensuring the normal growth of cells and controlling the transmission of signals. ⑥It can enhance insulin sensitivity and reduce the incidence of diabetes.

1.3 Curcumin

1.3.1 Properties of curcumin

Curcumin is a yellow pigment contained in the tubers of the perennial herb turmeric, and is an orange-yellow powder. Curcumin is a type of plant polyphenol, and includes three compounds: curcumin, demethoxycurcumin and bisdemethoxycurcumin.

Turmeric yellow pigment is insoluble in cold water, but soluble in ethanol, propylene glycol, glacial acetic acid and alkaline solutions. It is easily discolored by iron ions and has poor stability to light and heat. Turmeric yellow pigment is chemically reactive because its molecule contains multiple double bonds, phenolic hydroxyl groups and carbonyl groups. It has good coloring power, especially for proteins. Turmeric yellow pigment can be added according to production needs [17].

1.3.2 Functional properties of curcumin

Curcumin has a variety of physiological functions that are gradually being understood and studied. (1) Anti-mutagenic effect: Curcumin can metabolize mutagens and indirectly inhibit the metabolism of mutagens, thus having an anti-mutagenic effect. (2) Anti-tumor effect: It can eliminate free radicals, reduce the production of peroxides, inhibit the production of arachidonic acid metabolites, and inhibit the expression of cancer cells. ③Antioxidant effect: it can inhibit the oxidation of lipids in the air and by Fd and Cu2, inhibit the oxidation of hemoglobin by nitrous acid, and prevent the oxidative damage to DNA. ④Lipid-lowering and anti-atherosclerotic effects: it can inhibit the oxidation of modified low-density lipoprotein (LDL) in cells, and oxidized LDL plays an important role in atherosclerosis [2]. In addition, some data show that curcumin has a good inhibitory effect on most bacteria, especially Bacillus subtilis, Staphylococcus aureus and Escherichia coli. Therefore, curcumin has various physiological functions such as anti-inflammatory, anticoagulant, anti-infective and preventing the formation of age spots [6].

2 Safety issues with the consumption of natural coloring

Before each food coloring is approved, a large number of tests need to be carried out to provide a large amount of reliable data. Their safety is evaluated using a comprehensive evaluation method. The evaluation procedures vary from country to country, but the main factors considered are the toxicity of the coloring agent in animals, toxicological test data, and factors such as the chemical structure, properties, purity, impurities and stability of the coloring agent. As early as the 1980s and early 1990s, a large number of toxicological research reports conducted multiple animal tests and toxicological re-evaluations of existing synthetic food coloring agents. These include: amaranth, carmine, ponceau 4R, tartrazine, brilliant blue, indigo, allura red, etc. In 1994, the World Health Organization and the Joint Food and Agriculture Organization Expert Committee on Food Additives (JECFA) also published the toxicological evaluation results for certain colorants and proposed corresponding ADI values (maximum allowable daily intake by the human body). The 22 synthetic food colorants and their permitted scope and usage quantities stipulated in China's Hygienic Standards for Food Additive Use GB2760 are also based on the results of this evaluation. Therefore, the correct use of these 22 synthetic colorants within the maximum use limits is safe and reliable in China at present [18].

As can be seen from the attached table, natural coloring derived from food ingredients is safe. An ADI value has not been established for some natural colorings due to a lack of toxicity data. The ADI values for some natural colorings are relatively low and are not safer than synthetic colorings. JECPA's toxicity tests on natural colorings are rigorous and require the same standards as those for synthetic colorings, except that they must come from edible parts. The ADI values of the synthetic colors allowed for use in China, such as ponceau 4R and erythrosine, are relatively low, while those of the other colors are all above 2.5 mg/kg, which means that they are safe within a certain range of use [1].

This shows that “natural” is not equivalent to “safe”. Therefore, one cannot be blindly optimistic about the safety of natural coloring. In order to make natural coloring better serve mankind, all aspects of natural coloring production and the use process should be strictly controlled. In addition, it is urgent to establish testing methods and standards for natural coloring. The occurrence of the Sudan Red incident has drawn even more attention to the testing methods and standards for natural coloring.

3 Development trends and prospects for the consumption of natural coloring

Food coloring is a very important food additive, but the main ingredient of most synthetic colors is azo compounds (such as amaranth, carmine, sunset yellow, new red, lemon yellow, etc.), which are metabolized in the body to form substances such as B-naphthol and a-amino-1-naphthol, which are strongly carcinogenic. In addition, the product may also be mixed with pigment intermediates or produce toxic by-products (such as phenol, aniline, etc.), which also have a significant impact on human health. Therefore, synthetic food coloring is gradually being replaced by natural food coloring. The future direction of efforts in the field of edible natural coloring is to vigorously develop “natural, nutritious, and multifunctional” products, and to use high-tech methods such as genetic engineering, cell engineering, fermentation engineering, gel filtration, ultrafiltration, supercritical CO2 fluid extraction, affinity chromatography, and freeze-drying to improve the yield, increase the purity, ensure the quality, and reduce the cost of edible natural coloring [9].

With the development of cell biology, research departments have used callus tissue from red beets to produce betalain. Apple callus tissue is used to produce red pigments, and saffron cell cultures are used to produce saffron pigments and saffron acids. Grape cell suspensions are used to produce anthocyanins. And the root tissue culture of purple roots is used to produce purple root pigments. With the deepening of research, edible natural coloring will also be produced in the laboratory by cloning the required materials, so that the production of edible natural coloring can be industrialized.

While developing functional natural food coloring, practical research should also be strengthened. This requires research on the production of compound Natural Coloring, which can achieve new heights in terms of color, dosage form, stability, pH value, and adaptability to certain food applications through compounding, and ultimately fully meet the needs of a certain food, thereby making the application of Natural Coloring more convenient and extensive [9].

China's natural food coloring industry should seize the opportunity, based on the domestic market, open up the international market, and vigorously develop natural, nutritious, and multifunctional natural food colors (such as carotene, flavonoids, lycopene, etc.). At the same time, most toxic synthetic colors will be eliminated. The use of high-tech, continuous improvement of equipment levels, increase product output and intrinsic quality, reduce production costs, increase product competitiveness, new features of natural coloring will have broad market prospects

4 Summary

Food is the most important thing in people's lives, and it plays a very important role in their daily lives. As human society progresses and people's material living standards improve, and as people yearn for and pursue good health, products that return to nature and use natural ingredients are bound to become the mainstream of future food consumption. This is bound to set off a “green revolution” in the coloring industry, and Natural Coloring is bound to replace synthetic coloring.

Natural Food Coloring has a natural color and a wide variety of types. Many of its main ingredients are naturally found in food, and many Natural Food Coloring also have pharmacological effects and health benefits for the treatment and prevention of various human diseases. Natural Food Coloring is rapidly developing due to its safety, natural vibrant color, and wide range of uses, most of which are not limited by the amount added. With the development of the fields of naturalism, health and food toxicology, the development and application of natural coloring will become the general trend of the world's food coloring development. The varieties and application fields of natural food coloring will continue to expand, and the quality and functional effects of natural food coloring on the human body will continue to be strengthened.

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