Food additives are an important factor in the modern food industry. They play an extremely important role in improving the color, aroma and taste of food, increasing food nutrition, improving food quality, improving processing conditions, preventing food from spoiling, and extending the shelf life of food. Therefore, the food additive industry occupies an important position in the modern food industry.

01Definition and function of food additives

1. Definition of food additives

Food additives refer to artificial or natural substances added to food to improve its quality, color, aroma and taste, as well as for the needs of preservation and processing.

2. The role and development trend of food additives

1) The main function of food additives

a) It can improve the quality of food and meet people's requirements for food flavor, color and taste;

b) It can make food processing and manufacturing technology more reasonable, more hygienic and more convenient, and is conducive to the mechanization, automation and scale of the food industry;

c) It can help the food industry save resources and reduce costs, greatly improve the quality and grade of food, increase its added value, and generate significant economic and social benefits.

2) Development trend of food additives

a) Develop natural, nutritious and multifunctional food additives;

b) Strive to develop diversified and specialized additives.

02 Types of food additives

Food additives can be divided into natural food additives and artificial food additives according to their sources. According to their functions, they are mainly: nutritional enhancers, preservatives and mildew inhibitors, antioxidant preservatives, thickeners, emulsifiers, chelating agents (including stabilizers and coagulants), quality improvers, flavoring agents, color treatment agents, edible flavors, spices, etc.

1. Food preservatives

Food preservatives are a type of additive that is used to inhibit food corruption and deterioration and to extend the storage period and shelf life. Currently, there are four main types of food preservatives in common use: benzoic acid and its salts, sorbic acid and its salts, propionic acid and its salts, and parahydroxybenzoates.

1) Benzoic acid and its sodium salt

Benzoic acid, also known as benzoic acid, is a commonly used organic fungicide. In a low pH environment, benzoic acid is effective against a wide range of microorganisms, but has a weak effect on acid-producing bacteria. When the pH is higher than 5.5, it has no effect on many molds and yeasts. The most suitable pH value for benzoic acid to inhibit bacteria is 2.5-4, and the minimum mass fraction for complete inhibition of general microorganisms is 0.05% to 0.1%.

2) Sorbic acid and its salts

The chemical name of sorbic acid is 2,4-hexadienoic acid, which is a broad-spectrum food preservative.

3) Propionic acid and its salts

Propionic acid is a liquid with a stimulating sour aroma similar to acetic acid. Since it is a normal intermediate in human metabolism, it is non-toxic and its ADI value is not restricted. Propionic acid is effective against molds, aerobic bacteria, Gram-negative bacteria, especially against Escherichia coli that makes bread produce filamentous mucus, and can prevent the production of aflatoxin, so it is often used in the production of bread and pastries. Propionates have the same preservative effect, and calcium salts and sodium salts are commonly used.

4) Para-hydroxybenzoic acid and its esters

Parabens, also known as parabens, are colorless crystals or white crystalline powders, tasteless and odorless. They are mainly used in soy sauce, jam, soft drinks, etc. The preservative effect is better than benzoic acid and its sodium salt. The usage amount is about 1/10 of sodium benzoate, and the suitable pH value is 4-8. Parabens are less toxic than benzoic acid, and their water solubility is poor. They are usually dissolved in alcohol before use, and the price is also higher.

5) Natural food preservatives

Natural preservatives have the advantages of strong antibacterial properties, safety and non-toxicity, good water solubility, good thermal stability, and a wide range of effects. They are not only harmless to human health, but also have certain nutritional value. The natural preservatives developed in recent years include: natamycin, glucose oxidase, protamine, lysozyme, polylysine, chitosan, pectin decomposition products, propolis, tea polyphenols, etc.

2. Food emulsifiers and thickeners

Food emulsifiers and thickeners are additives that improve and stabilize the physical properties of food components or improve the texture of food. They play an important role in the "shape" and "quality" of food and the performance of food processing technology.

1) Emulsifier

Any food additive that can make immiscible liquids (such as oil and water) form a stable emulsion by adding a small amount is called an emulsifier.

① Fatty acid glycerides

Glycerol reacts with fatty acids to produce mono-, di- and tri-esters. Monoglycerides, also known as monoglycerides, are important food emulsifiers that are widely used in shortening, pastries, bread, candy and ice cream to emulsify, foam, prevent crystallization and resist aging.

②Sucrose fatty acid esters

Sucrose fatty acid ester is an emulsifier with excellent performance, high efficiency and safety. Sucrose fatty acid ester has sucrose as hydrophilic group and long carbon chain fatty acid as lipophilic group. It can be digested into sucrose and fatty acid in the body and absorbed. Sucrose fatty acid ester is non-toxic, non-irritating and easily biodegradable, so there is no restriction on its use in food.

③Sorbitan fatty acid ester

The trade name of sorbitan fatty acid ester is Span. Span-type emulsifiers react with ethylene oxide under base catalysis to obtain Tween-type emulsifiers.

④Soybean lecithin

Soybean lecithin, also known as soybean lecithin or phospholipid, is a light yellow or brown transparent, translucent viscous substance. It is a byproduct of soybean oil production and a natural surfactant. Its main components are lecithin, cephalin and inositol phospholipids. As an emulsifier, soybean lecithin has excellent emulsifying, antioxidant, dispersing and moisturizing properties. It has been widely used in food, instant milk, margarine, granular beverages, nutritional emulsifiers, etc.

2) Thickener

Thickeners are a type of food additive that can increase the viscosity of food and change its properties.

① Gelatin

Gelatin is a white or light yellow, translucent, slightly shiny flake or granule. Its main component is protein. It is a high molecular weight polypeptide polymer obtained by partial hydrolysis of collagen contained in animal skin, bones, cartilage, etc. Gelatin gel is tough, elastic, and has good pressure resistance. It dissolves in 30°C water and solidifies into a colloid after cooling.

② Maltodextrin

Maltodextrin, also known as water-soluble dextrin or enzymatic dextrin, is made from various types of starches through low-level controlled hydrolysis, conversion, purification and drying by enzymatic process. Maltodextrin is widely used in candy, malted milk, fruit tea, milk powder, ice cream, beverages, canned food and other foods. It is a filler and thickener for various foods.

③Pectin

Pectin is a polysaccharide substance widely found in plant tissues. Its main component is galacturonic acid. It is a recognized safe food additive recommended by the FAO/WHO Joint Committee on Food Additives and is not restricted by the amount of addition. At present, the main raw material for the production of pectin is citrus peel.

④Carrageenan

Carrageenan is a natural plant gum extracted from red algae. It is the youngest of the three major algae gums: alginate, agar and carrageenan. Its main components are D-galactose and L-galactose. Carrageenan is extracted from raw materials such as Eucheuma, Sand Vegetable and Chondrus. Carrageenan used in the food industry mainly has the characteristics of gelation, viscosity, stability, emulsification and suspension, and is widely used in dairy products, ice cream, fruit juice drinks, bread, hydrogel (jelly, etc.), meat products, canned food and other foods.

⑤ Xanthan gum

Xanthan gum is a safe, non-toxic, tasteless new food additive with excellent thickening, suspension, emulsification, stabilization and other functions. Xanthan gum is an extracellular heteropolysaccharide produced by Xanthomonas with starch as the main raw material through a series of biochemical reactions. Its main components are glucose, mannose, glucuronic acid, etc., with a molecular weight of up to millions. It is the most commercially valuable, largest-yield, and most widely marketed microbial polysaccharide product at home and abroad. Xanthan gum has excellent thickening properties and can achieve the required viscosity at a very low concentration. Xanthan gum can form a stable thickening system when it coexists with high concentrations of sugar or multiple salts.

3. Flavoring

Flavoring agents mainly include acidulants, sweeteners, salty agents and bittering agents. Among them, bittering agents are rarely used, and salty agents (generally salt) are not managed as food additives in my country. The following mainly introduces acidulants and sweeteners.

1) Acidulants

Food additives that are used to give food a sour taste are called acidulants. Sour taste can promote the secretion of digestive juices such as saliva, gastric juice, and bile, and have the effects of promoting appetite and aiding digestion. Its main functions also include regulating the pH value of food, acting as a synergist for antioxidants, preventing food from becoming rancid or browning, inhibiting the growth of microorganisms, and preventing food from spoiling. Acidulants mainly include organic acids: citric acid, lactic acid, tartaric acid, malic acid, fumaric acid, and adipic acid; inorganic acids,edible phosphoric acid, carbonic acid, etc.

①Citric acid

Citric acid is a colorless, transparent crystal or white powder with a mild, refreshing sour taste. It is commonly used in the manufacture of various beverages, sodas, wines, candies, snacks, biscuits, canned juices, dairy products and other foods.

②Malic acid

Malic acid is chemically known as carboxysuccinic acid or hydroxysuccinic acid, and is a white or fluorescent white solid. It has a special malic acid aroma and is widely used in yogurt, soda, ice cream, chewing gum, ketchup, jam, vinegar, fruit wine, margarine, etc. Malic acid is better than citric acid in terms of its sour taste, tastes close to natural fruit juice, and has a good pH adjustment effect. Using it instead of citric acid as an acidulant can save 20% of the dosage, and it can also cover up the odor produced by some sucrose substitutes.

2) Sweeteners

Sweeteners are food additives whose main purpose is to give food a sweet taste. According to their sources, they can be divided into two categories: natural sweeteners and synthetic sweeteners. Natural sweeteners are further divided into two categories: sugar and sugar derivatives, and non-sugar natural sweeteners. Artificial sweeteners are mainly some chemical substances with sweet taste, which are generally dozens to hundreds of times sweeter than sucrose, and most of them have no nutritional value.

①Saccharin and saccharin sodium

The chemical name of saccharin is o-sulfonylbenzoimide. It is calorie-free and highly sweet. The sweetness of saccharin sodium is 300-500 times that of sucrose. It is an early developed chemical synthetic sweetener. It has been used in food since the early 20th century. my country has a history of more than 60 years of production and use, with a production capacity of 40,000 tons/year, and is a major exporter in the world.

② Xylitol

Xylitol is a sugar alcohol made by reducing xylose or polyxylose in materials such as wood and corn cobs. Xylitol is a white crystal or crystalline powder with a refreshing sweet taste. Its sweetness is 65% to 100% of that of granulated sugar. Its calorific value is 12.5 kJ/g, which is higher than other sugar alcohols. It has the effect of inhibiting the activity of Proteus, which causes dental caries. In addition to the common properties of sucrose and glucose, xylitol also has special biochemical properties. It can be absorbed by the human body through the cell wall without the need for insulin, and has the functions of lowering blood lipids and resisting ketone bodies. It can be used to make beverages, candies, canned foods and other foods.

③Stevioside

Stevioside is a colorless or light yellow needle-shaped crystal with a melting point of 196℃～198℃. It is a mixture of various glycosides extracted from the plant stevia. It is relatively safe and about 300 times sweeter than sugar. Its taste is similar to that of sucrose, with pure sweetness, long retention time, delicious aftertaste, and is very stable to heat, acid and alkali, making it an ideal low-energy sweetener.

④Maltitol

The sweetness of maltitol is 0.8 to 0.9 times that of sucrose. It does not generate calories after ingestion, nor does it synthesize fat or stimulate the formation of cholesterol. The chemical properties of pure maltitol are very stable, and its heat resistance and acid resistance are better than sucrose, sorbitol and xylitol. Maltitol can resist the digestion of gastric juice, the hydrolysis of small intestinal enzymes and the decomposition of large intestinal microorganisms during human digestion. This special physiological property makes maltitol a high-end health sweetener with excellent taste and no calories.

⑤Aspartame

Its chemical name is asparagine phenylalanine methyl ester, and its relative molecular mass is 294.31. Aspartame is a new type of amino acid sweetener, with the appearance of white crystals or crystalline powder, and pH: 4.5-6.0. Aspartame has a pure sweetness like granulated sugar, and its sweetness is 200 times that of sucrose. It has no peculiar smell and has a synergistic effect on the flavor of food. It has good safety performance, does not require insulin to be involved in metabolism in the body, can be quickly digested and absorbed, and will not cause tooth decay.

⑥ Acesulfame potassium

Its chemical name is acesulfame potassium, and its molecular weight is 201.24. Acesulfame potassium is a white crystalline powder with high sweetness, which is about 200 times sweeter than sucrose (3% solution by mass).

⑦Other sweeteners

The main ones are oligofructose, erythritol, cyclamate, thaumatin, etc.

4. Food coloring

Additives used for food coloring are called food coloring, and their purpose is to increase the taste for food and stimulate appetite. Food coloring is divided into two categories according to its source: artificial synthetic coloring and natural coloring.

1) Artificial synthetic pigments

Artificial synthetic pigments include amaranth, carmine, erythrosine, new red, lemon yellow, sunset yellow, indigo yellow, brilliant blue, and aluminum lakes of various pigments to enhance the dispersion of the above water-soluble acidic pigments in oils and fats.

① Carmine

Carmine is a red to dark red powder. It is characterized by good acid and light resistance, but poor heat resistance and reduction resistance. It turns brown when it encounters alkali and is mostly used in cakes, beverages, agricultural and livestock aquatic product processing.

② Lemon yellow

Lemon yellow is an orange-yellow powder, which is widely used in cakes, beverages, agricultural and livestock aquatic product processing, medicine and cosmetics. It is characterized by good heat resistance, acid resistance, light resistance and salt resistance, poor oxidation resistance, slightly reddening when exposed to alkali, and fading when reduced.

2) Natural pigments

Natural pigments are extracted from animal and plant tissues using solvents. Although natural pigments are inferior in color and relatively less stable to light, heat, pH, etc., they are safer than synthetic pigments and have abundant sources. Some natural pigments also have vitamin activity or certain pharmacological functions. They are increasingly valued by people, and their production and sales are growing rapidly. The main products of edible natural pigments in my country include: caramel, red yeast rice and red yeast rice flour, red yeast red, capsicum oleoresin and capsicum red, gardenia yellow, gardenia blue, beet red, shellac red, etc.

03 General requirements and safe use of food additives

With the development of food toxicology, food additives that were originally considered harmless have been found to have chronic toxicity and teratogenic, mutagenic and carcinogenic hazards in recent years, so all countries have paid full attention to this.

At present, both international and domestic attitudes towards food additives are strict management, strengthened evaluation and restricted use. In order to ensure the safety of food additives, food additives should follow the following principles:

① Safety evaluation. The primary criterion for evaluating the toxicity (or safety) of food additives is the ADI value (daily intake by humans), and the second commonly used indicator for evaluating the safety of food additives is the LD50 value (median lethal dose, also known as the median lethal dose).

② Usage regulations. GB2760-2014 National Food Safety Standards and Food Additive Usage Standards stipulate the principles for the use of food additives, the types of food additives allowed for use, the scope of use, and the maximum usage or residue amount.