Study on 3 Popular Natural Food Color

Natural food color is a type of food additive that is extracted from animals, plants, microorganisms or microbial metabolites to change the color and nutritional properties of food. It has a long history, and natural pigments have been used in China since ancient times as dyes for textiles, rice, wine, cosmetics and other products. Today, natural food colors are widely used in beverages, alcoholic beverages, candy and baked goods.

Natural pigments used in baked goods such as sesame oil, chocolate pigments, red pigments, green pigments, and colored jams can be used to make custard buns, egg tarts and custard buns, fragrant cakes, glutinous rice balls, biscuits, cake fillings, dumplings and other products[1]. Oil-soluble natural pigments such as turmeric pigments are also often used in baked goods because they combine well with oil and fat. Red pigments are added to strawberry drinks, and natural brown pigments are added to osmanthus wine to make the colors more attractive.

In confectionery, they are often used to change the color of the candy and produce colorful sugar coatings to attract consumers. A long time ago, foreign countries already had methods of extracting plant pigments and adding them to candy. It is more widely used in meat products. It is well known that nitrite can protect the pigments in meat from being destroyed, which is extremely harmful to the body. In recent years, relevant scientific researchers have extracted paprika red for use in canned meat products, which is not only healthy and delicious, but also has good stability and achieves a better color development effect. Li Xing [2] and others studied three natural pigments that can replace nitrite, namely, nitrosoporphyrin, red yeast pigment and sorghum red pigment. Nitrosylhemoglobin not only ensures a bright color for meat products, but also reduces the nitrite content; red yeast pigment gives meat a special flavor and also has a bacteriostatic effect; sorghum red pigment is more light-resistant, and adding it to meat products gives a soft, natural color that attracts consumers.

In addition, natural food colors are safe to eat, have high physiological activity, are green and healthy, and can be extracted from a variety of animals, plants and microorganisms. Therefore, the international research and development of natural food colors is a major development trend. This article focuses on the nutritional effects and pharmacological properties of natural food colors, the research status of several popular natural pigments, and the outlook for future natural pigments.

1 Functional properties of natural food colors

Natural food colors are popular not only because they are colored substances extracted from plant tissues, animal tissues, microorganisms or microbial metabolites, and have bright colors that are harmless to human health, but also because they have certain nutritional effects and pharmacological properties and can be added as nutritional enhancers.

1.1 Nutritional effects

The most widely used is β-carotene, which is added to drinks to enhance their flavor. It is safe, has a balanced coloring power, and increases people's desire to eat. More importantly, carrot pigments can be converted to vitamin A in the human body, which has high nutritional value. The state has classified β-carotene as a nutrient fortifier for food fortification, which not only has antioxidant properties, but also prevents vitamin A deficiency and dry eye disease in the human body [3].

Yu Xiuzhuo and Kang Meiling [4-5] and others have studied the nutritional value of apple seed pigments. Apple seeds contain 25.3% fat, 34.0% protein, various macro- and trace elements, as well as some substances such as glycosides, alkaloids and tannins. They are rich in nutrients and will be added to various foods as a healthy and nutritious pigment.

The red pigment extracted from the peel of the red date has a rich and pure color, is relatively stable to heat and light, and has good water solubility. At the same time, it has the medicinal effects of eliminating free radicals, anti-oxidation, anti-tumor, anti-aging, nourishing the blood and vital energy, etc. Therefore, the study of red pigment from red dates has important practical value [6].

Natural pigments can be added as nutritional enhancers to enhance human function and health, and also have pharmacological effects such as disease prevention.

1.2 Pharmacological properties

Xu Chunming [7] et al. pointed out that gardenia yellow pigment contained in gardenia plants has certain antibacterial and pharmacological effects. It has a bright color, strong coloring power, good water solubility and stability.

Ancient Chinese medicine has conducted research on the pharmacological properties of red yeast rice pigment. Li Shizhen's Compendium of Materia Medica states that “it promotes digestion and blood circulation, strengthens the spleen and stomach” [8], and that “red yeast rice is used to promote digestion and blood circulation, strengthen the spleen and dry the stomach, treat red and white dysentery, promote the excretion of water and food, treat bruises and injuries, and treat women's blood pain and postpartum lochia that does not stop.” Wang Wenfeng[9] and others also pointed out that the medicinal effects of red yeast rice pigments have attracted widespread attention worldwide. They have a wide range of effects, such as anti-oxidation, kidney protection, blood pressure reduction, cardiovascular system protection, anti-cancer, and cholesterol reduction, and these have been carefully discussed one by one. A typical example is red fermented tofu, which is fermented with natural red yeast rice and therefore has antibacterial, blood pressure lowering, and blood fat and blood sugar lowering effects.

Other plant pigments such as red rice, licorice pigment, and perilla pigment, etc., are added to foods that need to be dyed during the cooking process, and have the effects of relieving coughs, strengthening the stomach, diuretic, and relieving pain[10]. Anthocyanins, a type of natural pigment found in fruits and vegetables, have been shown to have antioxidant and free radical scavenging properties, reduce serum and liver fat content, resist mutations and tumors, and prevent peroxidation in the body.

Anthocyanins, for example, are natural pigments that are widely found in plants. Not only do they have a bright color, but they also have the functions of nourishing the blood, nourishing the brain, benefiting the liver, diuretic, laxative, antioxidant and eliminating free radicals. They can be widely used in the food industry, health products and pharmaceutical industry [11-13].

Recently, the pharmacological properties of the popular red date pigment have been discovered one by one. Fan Litong [14] studied the anti-active oxygen function of dates, and the results showed that after treatment by different methods, there are certain differences in the anti-active oxygen function of dates, and some are even very significant. Xue Zi-ping [15] and others analyzed the optimization of the extraction process and the antioxidant activity of phenolic substances in the date peel, and the results showed that phenolic substances in the date peel have strong antioxidant capacity. Li Qian-qian and others [16] showed through the ULL test that the red pigment in the date peel contains active ingredients that inhibit the proliferation of K562 cells.

It can be seen that natural food colors have many pharmacological properties, and almost every natural food color has its own special medicinal function.

2 Research status of several popular natural colors

2.1 Red yeast rice pigment

Natural food colors are safer than synthetic colors, and do not carry the risk of causing cancer or genetic mutations. However, they are less stable and can easily lose their effects due to environmental influences. However, tests have shown that red yeast rice pigment has no toxic or mutagenic effect on the body, is highly safe, light-resistant, heat-resistant and chemically resistant[9], and has the characteristics of strong protein coloring power and soft tones compared to other natural pigments. Therefore, it is widely used in foods such as fermented tofu, pastries, candy, jam, fruit juice, etc. for coloring.

The many excellent properties of red yeast rice pigment, such as its water solubility, good dispersibility in injection solutions and marinades, ease of preparation, and color similar to natural meat color, make it widely used in meat products such as barbecued meat, ham, and sausages [17]. Wang Jinzi [18] and others pointed out that the coloring principles of red yeast rice pigment and nitrite are different. Nitrite forms nitrosomyoglobin with myoglobin, while red yeast rice pigment directly stains the meat. Both have the same coloring effect and flavor enhancement effect, inhibit the growth of harmful microorganisms, and thus extend the shelf life of the meat. However, as a natural pigment, red yeast rice pigment is non-toxic and harmless to the human body. The results of the German Meat Research Center also show that after adding red yeast rice pigment to cured products, the amount of nitrite can be reduced by 60%, while the flavor, color and storage properties of the cured food are not affected, and the color stability is also far superior to that of the original product.

In Taiwan, Honglu wine, in Fujian province, old red wine, and red wine produced in Niigata Prefecture, Japan, all use red yeast rice fermentation during the fermentation process. The resulting wine not only has a bright color, a rich aroma, and strong health benefits, but also does not deteriorate over time, but instead has even better characteristics [19].

Due to the many advantages of red yeast rice pigment, it has become a popular research object in the field of natural food coloring additives.

2.2 Red date skin pigment

Red date skin pigment is extracted from the red date skin, a waste product from the processing of red dates. It is a natural red pigment with good stability under various factors. It is a natural red pigment with good stability under various factors. It is a natural red pigment with good stability under various factors. It is a natural red pigment with good stability under various factors. It is a natural red pigment with good stability under various factors. It is a natural red pigment with good stability under various factors. It is a natural red pigment with good stability under various factors. It is a natural red pigment with good stability under various factors. It is a natural red pigment with good stability under various factors. It is a natural red pigment with good stability under various factors. It is a natural red pigment with good stability under various factors. It is a natural red pigment with good stability under various factors. It is a natural red pigment with good stability under various factors. It is a natural red pigment with good stability under various factors. It is In recent years, there have been a series of promising research developments in the extraction methods and stability of red date pigment.

The extraction processes of red date skin pigment generally include the following methods: solvent extraction, ultrasonic-assisted extraction, microwave-assisted extraction, enzymatic extraction, etc., and the latter extraction methods are often combined with the solvent method to improve the extraction rate. Among them, the solvent method has a high extraction rate, but it is time-consuming, has low extraction efficiency, and consumes a large amount of solvent [21]. However, the combination of ultrasonic, microwave, enzymatic and solvent extraction methods can not only overcome the shortcomings of solvent extraction alone, but also extract the red pigment from red dates in a safer, waste-free and pollution-free manner. Shi Hui [22] and others determined through experiments that the maximum absorption wavelength of zedoary red pigment is 656 nm, and the optimal extraction conditions are 0.01 mol/L NaOH and 70% ultrasound for 1.5 h. Li Yong [23] concluded in his research on the extraction of red pigment from the skin of jujube that column chromatography techniques such as AB-8 type perforated resin and Sephadex LH-20 are suitable for the separation of red pigment from the skin of jujube, providing a reference and basis for further research on the chemical composition of red pigment from the skin of jujube.

Li Qian [24] and others studied the stability of jujube fruit pigments, and the results showed that red pigment from the skin of jujube has high stability to light, temperature, Na+, K+, and neutral and alkaline solution environments. It has poor stability in acidic solution environments and some metal ions Mg2+, Ca2+, Zn2+, Cu2+, Fe2+, Fe3+, Mn2+, Pb2+, and Sr2+. It has strong stability towards carbohydrates, food additives, and preservatives, and poor stability towards redox agents.

2.3 Purple sweet potato anthocyanin pigment

Purple sweet potato anthocyanins are a type of natural pigment found in purple sweet potatoes. Many studies have shown that they have a number of physiological functions, such as anti-oxidation, elimination of free radicals, reducing the fat content in the blood serum and liver, anti-mutagenic and anti-tumor, and preventing peroxidation in the body. Due to the various bright colors, good coloring effect and strong physiological activity of anthocyanin pigments, they are popular with consumers and have broad market prospects [25].

Sun Jinhui [26] concluded the factors affecting purple sweet potato anthocyanins: under neutral to acidic conditions, purple sweet potato anthocyanins have a stable color and are the desired red or purple color of sweet potatoes. As the pH increases, the anthocyanins turn darker blue. Under acidic conditions, they have good heat resistance, slightly poor light resistance, poor stability to strong oxidants, slightly better stability to reducing agents, Most metal ions have little effect on it, while aluminum ions and iron ions have a color-enhancing effect. Health benefits include antioxidant, hypoglycemic, anti-inflammatory, liver protection, and anti-mutagenic effects. Some studies have also shown that anthocyanin pigments also improve eyesight[26].

Purple sweet potato anthocyanins are also widely used in food: during the brewing process, the presence of purple sweet potato anthocyanins gives the finished wine an attractive purple-red color, with a combination of the flavors of both wine and yellow wine. It is a low-alcohol fermented drink that is not only stable in nature, but also has health benefits such as anti-aging and anti-tumor properties. Anthocyanins are stable under acidic conditions and have good heat and light resistance, so they are widely used in acidic beverages such as carbonated drinks and fruit and vegetable drinks, where they provide good coloration and stability [27]. Yu Xiaoling and Yan Zheng and others have developed purple sweet potato-based foods such as jelly and low-sugar purple sweet potato preserves. These health foods do not contain any artificial colours or preservatives, and have a superior texture, with a special flavour and healthy nutritional properties. They are very popular with consumers.

3 Prospects for natural food coloring

Since 1992, China's food additive industry has proposed the green development policy of “natural, nutritious, multi-functional additives” and advocated the preferential use of natural colors in foods. After more than 10 years of development, China's natural color industry has made great progress in terms of industrial scale, market development, and production technology [28].

Scientific researchers are working on newer extraction methods to improve the extraction rate of natural pigments, such as enzyme engineering, supercritical CO2 extraction, affinity chromatography, microwave extraction, and gel filtration, to make the extraction of edible natural pigments more convenient, faster, and healthier, and to achieve large-scale production and then industrial production [3].

Yang Xinquan et al. [29] mentioned that in the development of new varieties of natural pigments and the improvement of existing varieties of technology, bio-high technology will become an important development direction. For example, the use of enzymatic technology to produce natural pigments largely satisfies consumers' psychological demand for natural products, and bio-high technology has low environmental pollution and is environmentally friendly green technology.

Natural pigments are gradually replacing synthetic pigments and are being used in an increasingly wide range of applications. This demonstrates people's desire for an environmentally friendly society, their pursuit of healthy food, and their use of the wisdom of nature. With the public's pursuit of health, the tireless hard work of scientific researchers, and the support of sufficient national project funds, the future of natural food colors is broad and bright.

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