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 agents to the food to adjust the color, in order to adapt to the needs of the majority of consumers.
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 colorants can be divided into a single and composite coloring agents.
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.
Characteristics of food colorants
(1) Natural colorants have a more natural and soft tone, which can bring man and nature closer together, but natural colorants have poor dyeing ability and uneven coloring; synthetic colorants have bright colors, which are welcomed by consumers, especially children and teenagers.
(2) Natural colorants generally come from plants and animals themselves, no toxic side effects on the human body, compared with synthetic colorants, higher safety, but synthetic colorants have strong coloring power, easy to dissolve, odorless, tasteless, inexpensive, and so on the advantages of the popularity of the people.
(3) Most of the natural colorants are sensitive to light and heat, metal, acid and alkali, oxidant, in these conditions is not stable, the color tone will change greatly, and 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 prefer to use natural antioxidants and preservatives.
(5) Most of the natural coloring agents also have both nutritional value and pharmacological effects, food coloring agents in the medical field also has great prospects for application. For example, red kale pigment has a good effect on human heart disease and atherosclerosis.
Stabilizing factors of food colorants
The breakthrough point of natural colorants is to improve their quality and stability, and chemists in various countries have done a lot of research for this. Generally, the stability of natural coloring agent is studied in the following aspects: (1) Light factor.
(1) Light factor. It refers to the color change of colorants under direct sunlight, for example, chlorophyll is widely found in the leaves and stems of plants, which is easy to decompose when exposed to light, and 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 with high Vc content, its stability can be improved.
(3) Acid-base factor. It refers to the coloring agent in acidic or alkaline conditions to show the color and stability changes, such as β-carotene widely exist in carrots and algae, in the weak alkaline condition is more stable, but in the acidic condition is easy to decompose, if you add a small amount of Vc can improve its stability; rosehip pigment color with the solution of the pH changes and changes, acidic conditions is red, neutral is purple, alkaline is blue.
(4) Metal ion factor. Commonly, there are copper ions, sodium ions, magnesium ions, iron ions and so on, gardenia pigment is not strong to iron ions, some metal ions can make the colorant change color or even fade out, and some metal ions can make some colorant stability enhancement, 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, adding a small amount of Vc can greatly improve its stability.
(6) Some compounds such as sucrose, alum, tartaric acid salt factor. For example, the yellow pigment in the addition of alum and tartaric acid salt after its stability can be significantly increased.
(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 colorants also have a certain effect on the colorant itself.
Colorants used in food
First, 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 concentrate, and then dried and processed to obtain purple-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 reduced, but also for high sugar juice drinks, carbonated beverages, prepared wine, candy and so on.
Second, 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, cochineal carmine carmine, alias 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 dark 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 add boiling water slowly under stirring, and the water used must be distilled water or deionized water.
Colorants used in seasonings
I. Caramel pigment 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 amount of the largest and most popular of a 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.
Second, curcumin curcumin, molecular formula C21H20O6, relative molecular mass of 368.37, is a chemical component extracted from the rhizomes of some plants in the ginger family, Tennessee family, is a very rare pigment with diketone in the plant world, a diketone compound.
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.