Study on Natural Red Food Coloring

In traditional Chinese food culture, people tend to pay attention to the reasonable matching of color, fragrance and taste. Bright and beautiful colors can make people feel happy and enhance their appetite. With the improvement of living standards, industrialization of food has gradually become an important part of people's daily diet. Pigments are favored by all industries because they can give food an attractive color and enhance people's desire to buy. Food colorants are mainly divided into two types: synthetic and natural. In 1856, W H Perkins of the United Kingdom first synthesized the organic pigment aniline violet. Since then, synthetic colorants have rapidly dominated the food coloring market due to their high performance and low price. However, as more and more research reports on the hazards of synthetic colorants appear, people have huge doubts about synthetic colorants. Consumers prefer foods with natural colorants added or labeled as “non-artificial” and “all-natural” [2].

The development of natural colorants has become an inevitable trend. Natural food coloring is a natural pigment obtained from various organisms, including microbial, plant, animal and mineral pigments, with plant-based colorants accounting for the majority. It is a safe, non-toxic, nutrient-rich, healthy natural additive. Some natural pigments not only have the effect of coloring food, but also have physiological activity and have broad development and application prospects [3]. Among food colorants, red pigments are a very important type of food coloring. Red tones can stimulate the human brain and give a sense of excitement, as well as having the effect of increasing appetite and enhancing the desire to buy. This article will focus on several commonly used edible Natural Red Food Coloring with health benefits, with the aim of promoting the development of the pigment industry.

1 Natural sources of Natural Red Food Coloring

Natural Red Food Coloring generally includes several types such as carotenoids, flavonoids, porphyrins, polyphenols, anthocyanins, and quinones. They are mainly extracted from plant fruits, such as annatto extraet, tomato color and paprika oleoresin. The most studied one is paprika red, which contains more than 50 kinds of carotenoids. The shells of some crustaceans are also an important source of carotenoid-based red pigments, as they are composed mainly of the polyene pigment astaxanthin and a small amount of β-carotene. Anthocyanin-based red pigments are mainly found in the fruits, roots, stems and leaves of plants, such as blaek bean red, beet red and mulberry red. Flavonoid pigments have antioxidant properties, and the most produced flavonoid red pigment is sorghum red (Sorghum Red). Quinone pigments are derivatives of quinones and have antibacterial, antiviral, and anticancer effects. Some quinone pigments come from plants and insects and are important coenzymes in the biological oxidation pathway, such as Jujube Pigment and Carmines. Porphyrin red pigments only refer to blood pigments, which are often used instead of nitrites to color meat products, such as phycoerythrin. The most common polyphenol red pigment is tea red pigment (Tea Red Pigment), which also has a specific inhibitory effect on the HIV reverse transcriptase. In addition, there are red yeast rice pigment and Antarctic red pigment, which are made from microorganisms, and gardenia red pigment, which has been artificially modified [4].

2 Research status of several natural red food coloring

2. 1 Monascus red

As a kind of pigment produced by the secondary metabolism of red yeast rice, red yeast rice red pigment is mainly made from rice and soybeans. Based on the traditional red yeast rice production process in China, it is first produced through the liquid fermentation of red yeast rice, and then the advanced modern biological separation technology is used to obtain a pure natural, non-toxic natural food coloring in powder form. It is currently the only natural pigment in the world that is produced by microbial fermentation, and has always been recognized at home and abroad as one of the safer food coloring. Studies have shown that red yeast rice pigment has physiological activities such as lowering blood lipids and blood pressure, anti-mutagenic, anticancer and preservative properties, and is stable under the influence of light, heat and metal ions [5].

Li Shanshan et al. [6] studied the application of red yeast rice pigment as a nitrite substitute in Sichuan-style sausage. Whether packaged in light-protected or transparent packaging, the red yeast rice pigment can achieve the same sodium nitrite addition level of 0.12 g/kg after 27 days of storage when added at a rate of 0.12 g/kg. Nowadays, in addition to being used as a preservative and coloring agent for meat products, red yeast rice pigment is also widely used in industries such as the wine industry, condiment industry, flour products industry, and textile industry [7]. Currently, the most widely used method for extracting red yeast rice pigment is ultrasonic-assisted extraction. To improve extraction efficiency, research can be carried out on the secondary metabolites of red yeast rice, starting with the relevant gene PKS [8].

2. 2 Cochineal red pigment

Cochineal red pigment (cochineal) is a natural pigment extracted from the female cochineal insect on cacti, with a pink to purplish red hue. As a natural dye derived from insects, it has a long history [9]. Because it is an anthraquinone natural pigment with very stable physical and chemical properties, it is considered the safest natural pigment and is widely used in the production of food, cosmetics, pharmaceuticals, textiles, etc. Liu Lanxiang et al. [10] used acetic anhydride/acetic acid as the reaction system and dodecyl succinic anhydride (DDSA) as the esterifying agent to chemically modify the carmine acid molecule, and the resulting oil-soluble carmine derivatives both had good oil solubility and stability.

At present, high-performance liquid chromatography is mainly used to determine the content of cochineal pigments in various foods [11]. Carmine, which differs from cochineal red pigment by one character, is an azo synthetic pigment. In routine inspection and quarantine, it is often found that some enterprises confuse the use of the two, which poses certain food safety risks. Hua Congling et al. [12] compared carmine and carmoisine in their research and analysis, and proposed countermeasures in three areas: enterprise quality systems, supervision models, and information exchange. Carmine not only has excellent dyeing ability, but also has the advantages of high safety and health, and is believed to have a very broad application prospect.

2. 3 Red date pigment

Jujube is a kind of edible food, which is not only rich in nutrients, but also has medical and health care effects, and is rich in natural red color with bright color. Jujube pigment is a kind of natural pigment extracted from the skin and residue of jujube. Compared with other synthetic red pigments, it has bright color, strong jujube fragrance, safety and non-toxicity, and good stability. can not only be used to color fruit drinks and foods, but also to enhance the flavor. WH Yao et al. [13] determined the optimal extraction process for red date pigment by water bath extraction: the extraction solution was 0.8039% NaOH, the temperature was 81.2 °C, and the extraction time was 3.09 h.

Studies have found [14-15] that the use of microwave and ultrasound during extraction can effectively improve efficiency. Yue Li et al. [16] used Aspergillus niger as the fermentation strain and determined that the optimal fermentation conditions for the liquid fermentation of Aspergillus niger to assist in the extraction of red jujube pigment were: fermentation temperature 30 °C, fermentation time 5 d, carbon-to-nitrogen ratio 5:1, with the jujube peel as the fixed carbon source and sodium nitrate as the nitrogen source. As is well known, natural pigments have a common problem: they are unstable. Jujube pigments are easily soluble in a medium alkaline environment and easily precipitate in an acidic environment. The structure of jujube pigments may be damaged after being treated with high temperatures and strong acids. Sodium benzoate has almost no effect on the stability of jujube red pigment, while potassium sorbate has the most serious effect on its stability [17]. You Feng et al. [18] found that the red date pigment solution contains polyphenols, flavonoids and resorcinol structural substances through color development reaction, ultraviolet-visible spectroscopy and IR spectroscopy analysis, among which flavonoids are mainly dihydroflavonoids. According to research, red date pigment is a flavonoid pigment that has the pharmacological effects of scavenging free radicals, anti-oxidation, anti-aging, preventing cardiovascular and cerebrovascular diseases, lowering blood pressure, lowering blood lipids, lowering blood sugar, etc., and can be used in the research and development of anti-cancer, anti-oxidation and other health products, lipsticks and anti-aging cosmetics [19].

2. 4 Antarctic red pigment

Antarctic red pigment is a pigment-producing fungus Geomyces WNF-15A isolated and purified from an Antarctic soil sample. After analyzing its colony characteristics, microscopic morphology observations and ITS sequences, it was classified as Geomyces. Studies have shown that the pigment produced by this Antarctic fungus is a red powder [20]. The application of red yeast rice pigment is limited because a mycotoxin harmful to humans and animals, patulin, was detected in red yeast rice fermentates.

In recent years, researchers have been exploring safer microbial pigments and have compared this Antarctic fungal pigment with existing pigments. Jin Binbin [21] optimized the fermentation conditions of Antarctic red pigment and explored and analyzed the composition and physiological activity of Antarctic red pigment Geomyces sp. WNF-15A. The study showed that the ability and stability of this fungus to secrete pigments is higher than that of similar species, and it also has antioxidant, reducing and antibacterial properties. Liu Jie et al. [22] found that the color value (155.2) of the red pigment produced by the Antarctic fungus Geomyces sp. WNF-15A is significantly higher than that of the red yeast rice pigment (86.4), and some of its properties are also superior to those of red yeast rice pigment, such as antioxidant capacity, acid stability and food additive stability. It is expected to become a substitute for cochineal red pigment. Antarctic red pigment is a fungal pigment. Fungi have unique advantages in producing pigments, and the use of fungi to produce pigments will gradually become a trend in the food industry.

3 Conclusion

The complex structure of Natural Red Food Coloring makes it less stable than synthetic coloring. At the same time, synthetic coloring is more convenient for food coloring applications due to its clear structure and high purity. However, when synthetic coloring exceeds the specified concentration or is used improperly, it will cause great harm to the human body. Natural Red Food Coloring is extremely abundant and has a good health-promoting effect. Although the production of Natural Red Food Coloring in China is increasing year by year, the supply still falls short of demand. Current research on Natural Red Food Coloring focuses on extraction and separation and rapid determination. Therefore, it is necessary to accelerate technological reform and innovation in factories to produce more pure, high-quality and environmentally friendly Natural Red Food Coloring. In addition, since the cost of extracting Natural Red Food Coloring from plants is high, research and development on microorganisms will be the future direction of development for natural pigments.

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