What are the applications of food colorants?

Color is one of the important criteria for evaluating the quality of food appearance, people in judging the good or bad food often first observe its color, natural, soft, pleasing to the eye color can stimulate people’s appetite, increase the consumer’s desire to buy; on the contrary, if the food in the process of production, processing, transportation, discoloration or fading, the quality of the food will be greatly compromised. Usually, we add food coloring agent in food to adjust the color to meet the needs of consumers.
1、 Classification
According to the source of colorants can be divided into synthetic colorants and natural colorants; according to the structure, synthetic colorants can be divided into azo, anthracene and dibenzomethane, etc.; natural colorants can be divided into pyrroles, polyenes, ketones, quinones and polyphenols, etc.; according to the solubility of the colorants can be divided into fat-soluble and water-soluble colorants; according to the composition of the colorant is divided into a single and composite coloring agent.

Natural colorant color is susceptible to metal ions, water quality, pH value, oxidation, light, temperature, generally more difficult to disperse, dyeing, colorants between the poorer compatibility, and high prices. The raw materials of synthetic colorants are mainly chemical products, compared with natural pigments, the color of synthetic pigments is more vivid, not easy to fade, and the price is lower.

2, the characteristics of food coloring agents

(1) Natural colorants are more natural and soft hues, which can bring people closer to the relationship between nature, but natural colorants have poor dyeing ability and uneven dyeing; synthetic colorants are brightly colored, which are welcomed by consumers, especially children and teenagers.

(2) Natural colorants generally come from plants and animals themselves, no toxic side effects on human body, compared with synthetic colorants, safety is higher, but synthetic colorants have the advantages of strong coloring power, easy to dissolve, odorless, tasteless, cheap and so on and are very popular.

(3) Most of the natural colorants are sensitive to light and heat, metal, acid and alkali, oxidizing agent, unstable under these conditions, the hue will change greatly, while synthetic colorants can make up for this shortcoming.

(4) Some natural colorants can be used as natural antioxidants and natural preservatives. Due to the safety problems of synthetic antioxidants and preservatives, more and more consumers tend to use natural antioxidants and preservatives.

(5) Most of the natural coloring agents also have nutritional value and pharmacological effects, and food coloring agents have great application prospects in the medical field. For example, red kale pigment has been shown to be effective against heart disease and atherosclerosis in humans.

3, food coloring agent stabilizing factors
The breakthrough point of the study of natural colorants is to improve their quality and stability, chemists in various countries have done a lot of research for this. Usually, the stability of natural colorants are studied in the following aspects: (1) Light factor.

(1) Light factor. It refers to the color change of the colorant under direct sunlight, for example, chlorophyll is widely found in the leaves and stems of plants, it is easy to decompose when exposed to light, in order to improve its stability, it is usually made into copper sodium salt.

(2) Temperature factor. Considering the heat resistance of coloring agent, saffron yellow pigment has poor heat resistance, if used in food containing high Vc can improve its stability.

(3) Acid-base factor. Refers to the coloring agent in acidic or alkaline conditions and the stability of the color changes, such as β-carotene widely present in carrots and algae, in the weak alkaline conditions are more stable, but easy to decompose in acidic conditions, if you add a small amount of Vc can improve its stability; rosehip pigment color changes with the pH value of the solution changes, acidic conditions was red, neutral purple, alkaline was blue.

(4) Metal ion factor. Commonly, there are copper ions, sodium ions, magnesium ions, iron ions, etc. Gardenia pigment is not very tolerant to iron ions, some metal ions can make the colorant change color or even fade out, while some metal ions can make some colorants increase stability, such as chlorophyll made of copper sodium salt can improve stability.

(5) Antioxidant and reducing agent factors. Commonly used antioxidants are Vc, sodium thiosulfate, for example, saffron yellow pigment due to heat resistance is not good, sensitive to metal ions, add a small amount of Vc can greatly improve its stability.

(6) Some compounds such as sucrose, alum, tartrate factor. For example, the stability of yellow pigment can be increased after adding alum and tartaric acid salt.

(7) Some colorants and another colorant combination of its stability can also be improved, such as beet red and vegetable color red two colorants combined with each other after the stability of the obvious increase.

(8) Solubility factors. Grape skin pigment and perilla pigment are water-soluble colorants, while red rice pigment and comfrey pigment are fat-soluble colorants. In addition, the salt resistance and microbial resistance of the coloring agent also has a certain effect on the coloring agent itself.

4、Colorants used in foodstuffs

I. Amaranth Red
Amaranth red, also known as acid red, prune red, cockle red, edible red pigment No. 2. The main coloring components are amaranthin and betaine. Amaranth red is based on the edible part of red amaranth as raw material, extracted with water, refined with ethanol to obtain the concentrated liquid, and then dried and processed to obtain the purplish-red dry powdery finished product. Amaranth red is easily hygroscopic and soluble in water and dilute ethanol solution.

The solution is purplish red and clear when the pH is less than 7, insoluble in anhydrous ethanol, petroleum ether and other organic solvents. It has poor stability to light and heat, and metal ions such as copper and iron have a negative effect on its stability. pH value is greater than 9, the solution of this product changes from purple red to yellow.

Amaranth red is often used in the production of pickled vegetables, etc., the maximum use of 0.05g/kg. Amaranth red is sensitive to oxidation, reduction, not for fermented foods and foods containing reduction, but also for high-sugar fruit juice drinks, carbonated beverages, prepared wine, candy and so on.

Lemon Yellow
Lemon yellow, also known as tartar yellow, acidic yellow, hydrazine yellow, edible yellow 4, molecular formula C16H9N4Na3O9S2, relative molecular mass 534.37. Lemon yellow is orange-yellow to orange particles or powder, odorless. Soluble in water, 0.1% aqueous solution is yellow. Soluble in glycerol, propylene glycol, slightly soluble in ethanol, insoluble in oil. Light resistance, heat resistance, acid resistance, salt resistance are good, poor oxidation resistance, color fading in reduction.

Stable in citric acid and tartaric acid. Slightly red in alkali, strong coloring power, high firmness. Lemon yellow is often used in jams, stained vegetables and so on. Lemon yellow is a relatively stable coloring agent, can be used in combination with other pigments, good match. Is the most used in food yellow pigment, widely used, accounting for more than 1/4 of all food coloring.

Third, carmine
Carmine red, also known as Lichun red 4R, red, bright scarlet cochineal red acid, insect red, C.I. natural red 4. Molecular formula is C20H11N20O10S3Na3, relative molecular mass 604.48. Carmine is red to deep red particles or powder, odorless. Easily soluble in water, aqueous solution is red, solubility in water at 20 ℃ is 23%. Slightly soluble in ethanol, soluble in glycerol, insoluble in oil. Carmine red is highly hygroscopic. Maximum absorption wavelength of 508nm or so. Good light resistance and acid resistance, stable to citric acid and tartaric acid. Weak coloring properties.

When used in practice, cochineal is sensitive to oxidation and reduction, and is not suitable for fermented foods and foods containing reducing substances. If it is mixed with other coloring agents, it should be proportionally converted according to the maximum usage amount, and its dosage should not exceed the permitted amount of single coloring agent. It is advisable to mix it with a small amount of cold water first, and then slowly add boiling water under stirring, and the water used must be distilled water or deionized water.
5、 Colorants used in season ings

Caramel coloring
Caramel pigment, also known as caramel, English name Caramel, caramel pigment is one of the longest history of human use of food coloring, but also the current use of additives in the largest amount of the most popular kind of man-made natural coloring.

It is characterized as dark brown to black liquid or solid, with special sweet aroma and pleasant burnt bitterness, easily soluble in water, insoluble in usual organic solvents and oils and fats. The aqueous solution is reddish brown, transparent without turbidity or precipitation. It is light and heat stable, has colloidal properties, has an isoelectric point, and its pH value is usually around 3~4.5.

Caramel pigment is often used in the production of soy sauce and vinegar in condiments to enhance the color. According to GB 2760-2014, caramel color pigment produced by common method is applicable to soy sauce, vinegar, compound seasoning and sauce and sauce products. The caramel pigment used in soy sauce must be salt-resistant, otherwise it is very easy to precipitate; meanwhile, in order to improve the red brightness and wall-hanging of soy sauce, it is necessary to choose varieties with high red index and solid content. Caramel pigments used in vinegar are generally acid-resistant, otherwise they will fade in a short period of time. The main types and dosages of caramel colorants applied in soy sauce and vinegar are shown in Table 1.

Second, curcumin
Curcumin, molecular formula C21H20O6, relative molecular mass of 368.37, is a chemical component extracted from the rhizome of some plants in the ginger family, Tennessee family, is a very rare pigment with diketone in the plant world, for diketone compounds.

Curcumin is an orange-yellow crystalline powder with a slightly bitter taste. Insoluble in water, soluble in ethanol, propylene glycol, soluble in glacial acetic acid and alkaline solution, reddish brown in alkaline, yellow in neutral and acidic. Strong stability to reducing agents, but sensitive to light, heat, iron ions, light resistance, heat resistance, resistance to iron ions is poor. Curcumin has the efficacy of hypolipidemic, antioxidant, anti-inflammatory, anti-atherosclerosis, anti-cancer and so on. It is often used in curry powder, mustard sauce, etc. for coloring and flavoring.

References:

[1] Wei Ying, Wu Zhixiang. Brief description of the application of colorants in condiments and foods. China Seasoning May 2014, Volume 39, Issue 5

[2] Chen J. Progress of application research on food colorants. Journal of Langfang Normal College ( Natural Science Edition) August 2011, Volume 11, Issue 4