Types of Natural Food Coloring and Extraction Methods

Pigments are substances that give organisms a variety of different colors, among which edible pigments are developed and extracted and are widely used as an important food additive in the production and research of food.

Natural pigments are edible pigments obtained from natural resources, mainly extracted from animal and plant tissues and microorganisms (cultures), of which plant-based colorants account for the majority. Compared with synthetic pigments, they are safe, non-toxic, no side effects, many natural pigments contain essential nutrients or are themselves vitamins or substances with the nature of vitamins, such as riboflavin, β-carotene, and some natural pigments have certain pharmacological effects, preventive and therapeutic effects on certain diseases, such as rue.

Types of Natural Pigments

Natural pigments are divided into three categories according to their sources: plant pigments, such as carotene in carrots, lycopene in tomatoes, etc.; animal pigments, such as hemoglobin in muscles, astaxanthin in shrimp shells, etc.; and microbial pigments, such as red currant pigments on the surface of soybean curd.

1.1Plant Pigments

Plant pigments are widely distributed in herbal plants, including fat-soluble chloroplast pigments and water-soluble cytosol pigments.

The former exists in chloroplasts, related to photosynthesis, this kind of pigment is insoluble in water, difficult to dissolve in methanol, and easily soluble in high concentrations of ethanol, ether, chloroform, benzene and other organic solvents, chlorophyll itself has an antibacterial effect, and it can be prepared into anti-inflammatory drugs.

The latter exists in the vesicles, especially with the color of the flowers, mainly anthocyanosides, also known as anthocyanins, commonly found in flowers, soluble in water and ethanol, insoluble in ether, chloroform and other organic solvents, lead acetate reagent will be precipitated and adsorbed by activated charcoal, and its color with the pH of the different and will change. Its color will change with different pH. Flower chromoside is often removed as an impurity in the preparation of herbal preparations or the extraction of active ingredients.

1.2 Animal Pigment

Animal pigments are mainly distributed in the muscle, circulatory system, visual organs body surface, and other parts of the body, mostly by the nerve signals caused by the role of the endocrine system to produce, with specific physiological functions.

Natural pigments for food animal resources are less, focusing on certain large mammals, such as the extraction of bilirubin, hemoglobin consumption of livestock, and the animal kingdom in the richest variety of insect resources are little development and utilization, has been reported that the development of the better 2 kinds of insects are purple gummy worms and cochineal insects.

1.3 Microbial Pigments

The most researched and applied natural food microbial pigment is erythrulose, which is a high-quality natural food pigment produced by the fermentation of filamentous fungi of the genus Aspergillus and is a secondary metabolite of Aspergillus erythrorhizus.

Red currant pigment, the commercial name of red currant red, is rice, with soybean as the main raw material, by Aspergillus erythrorhizus liquid fermentation culture, extraction, concentration, refining, and red currant rice as raw material, extraction, concentration, refining and made of natural red pigment.

With the advantages of high safety and good process performance, it has been widely used for coloring meat, beans, noodles, sugar, jam, juice, and other types of food.

Extraction Methods of Natural Food Coloring

2.1 Solvent Extraction Method

The most commonly used solvent extraction method is a mass transfer process according to the differences in the polarity of the extracted components in the raw material and the physicochemical properties of the coexisting impurities, following the principle of similar dissolution, so that the active ingredients from the solid surface of the raw material or the tissue inside the solvent to transfer the mass transfer process.

2.2 Enzyme Extraction Technology

For some of the raw materials surrounded by the cell wall is not easy to extract the enzyme extraction method can be used such as Xue Weiming et al. cellulose enzyme extraction process to extract saffron yellow pigment in safflower, compared with the traditional water immersion extraction process, the extraction rate is greatly improved.

2.3 Microwave-Assisted Extraction Technology

Microwave extraction through microwave heating and sample contact solvent, the use of microwave absorption in the microwave field of microwave capacity differences make some areas of the matrix material or extraction system of certain components selective heating so that the extracted material from the matrix and system separation. This technology is characterized by high selectivity, short extraction time, low solvent consumption, high extraction rate of pigment components, no noise, low operating cost, reduced raw material pretreatment and environmental friendliness, and is suitable for thermally unstable substances.

2.4 Ultrasonic Extraction Technology

The basic principle of the ultrasonic extraction method is to use ultrasonic cavitation to accelerate the dissolution of active ingredients in plants, in addition to the secondary effects of ultrasonic waves, such as mechanical vibration, emulsification, diffusion, crushing, chemical effects, etc., can also accelerate the diffusion of the components to be extracted to release, and fully mixed with the solvent to facilitate the extraction of ultrasonic crushing, stirring, and other special effects can break the wall of the plant cell, to make the solvent as soon as possible penetrate the plant cell. Ultrasonic crushing and stirring can break the plant cell wall so that the solvent can penetrate the plant cells as soon as possible and dissolve the active ingredients. Liu Xiaoxuan et al. used ultrasonic technology to extract the yellow pigment of Mimulus lanceolatus, with a simple method, short operation time, and high extraction rate.

2.5 Molecular Distillation Technology

The basic principle of this technology is based on the difference of the average free range of molecular motion of different substances under high vacuum and separates them under the condition of far lower temperatures than the boiling point of substances at atmospheric pressure.

This technology has the characteristics of low distillation temperature, low distillation pressure, high degree of separation, short heating time, etc., thus it can greatly reduce the separation cost of high-boiling point materials, protect the quality of heat-sensitive materials extremely well, and truly maintain the characteristics of the pure natural.

Molecular distillation technology is suitable for the separation and purification of high value-added components in crude products, which is difficult to accomplish by other commonly used separation means.