What Is an Emulsifier?

Emulsifiers are a class of compounds that make a mixed liquid of two or more incompatible components into a stable emulsion. The principle is that during the emulsification process, the dispersed phase is dispersed in the continuous phase in the form of droplets (micron level). The emulsifier reduces the interfacial tension of each component in the mixed system and forms a stronger film on the surface of the droplets. Or due to the charge given by the emulsifier, an electric double layer is formed on the surface of the droplets, preventing the droplets from aggregating with each other, and maintaining a uniform emulsion. From a phase perspective, the emulsion is still a heterogeneous system. The dispersed phase in the emulsion can be either the water phase or the oil phase, most of which are the oil phase; the continuous phase can be the oil phase or the water phase, and most of the water phase. Emulsifier is a kind of surfactant, which has hydrophilic group and lipophilic group in the molecule. In order to indicate the hydrophilicity or lipophilicity of emulsifiers, the "hydrophilic-lipophilic balance (HLB value)" is generally used. The lower the HLB value, the stronger the lipophilicity; conversely, the higher the HLB value, the more hydrophilic Strong. Different emulsifiers have different HLB values. In order to obtain a stable emulsion, a suitable emulsifier must be selected. ^[1]

Emulsifier refers to a substance that can improve the surface tension between various constituent phases in an emulsion to form a uniform dispersion or emulsion. Food emulsifiers are among the 22 types of food additives specified in GB 2760-2014 "Standards for the Use of Food Additives." One. The amount of food emulsifier accounts for about 1/2 of the total amount of food additives. It is the most used additive in the food industry. It plays an important role in food production and food processing. Almost all food production and processing involve emulsifiers or emulsifiers. effect. Food emulsifier is a kind of multifunctional and highly efficient food additive. In addition to its typical surface activity, it also has the functions of defoaming, thickening, stabilizing, lubricating and protecting in food. ^[2]

Food emulsifier is a method of physically dispersing two or more mutually incompatible phases (such as oil and water) to form a dispersed active substance uniformly. It occupies a very important position in the food industry, can improve food quality, prevent food spoilage, extend the shelf life of food, improve the taste and appearance of food, and stimulate consumer demand. Its emulsification properties depend on the hydrophilic-lipophilic balance (HLB value) of the emulsifier. The larger the HLB value, the stronger its hydrophilicity, and conversely, the stronger its lipophilicity. ^[4]

There are now dozens of food emulsifiers commonly used in China, and different emulsifiers can be selected according to different purposes. Emulsifiers can be divided into ionic surfactants (anionic surfactants such as carboxylic acid, sulfate, etc., and cationic surfactants such as polyacrylamide, fatty amine salts, etc.) and non-ionic surfactants based on whether they contain hydrophilic groups Surfactants (Tween, Span, etc.). In addition, there are, for example, amino acid-type amphoteric surfactants and complex-type surfactants. According to its source, it can be divided into natural surfactants (such as lecithin, certain proteins, etc.) and synthetic surfactants (such as polyacrylamide, polyglycerides, etc.). According to the size of the emulsifier HLB value, it can be divided into lipophilic surfactants (HLB value less than 10, such as Span) and hydrophilic surfactants (HLB value greater than 10, such as Tween). The properties of emulsifiers are different. In today's food processing industry, in order to improve the function of food emulsifiers, different emulsifiers are often mixed and used. The common method is to adjust the hydrophilic-lipophilic balance of emulsifiers ( HLB), change the hydrophilicity and lipophilicity, determine the type of emulsifier, make it have wider practical adaptability. ^[4]

The Joint FAO / WHO Expert Commit-tee on Food Additives (JECFA) is an authoritative organization for international food additive safety evaluation established in 1956. It has established a daily allowable intake The quantity (ADI value) and related product specifications of food additives are widely used and referenced internationally. ^[2]

The development of emulsifiers in China has been for more than 30 years, but there are still many problems, such as "what is an emulsifier?" The most basic question is not clear to many people. In 2015, the world's top journal "Nature" published a question about the safety of emulsifiers in the article "Dietary emulsifiers affect the intestinal microbiota in mice and promote colitis and metabolic syndrome." Think of food emulsifiers, this is incorrect, so the article is meaningless. As emulsifiers, the following two points are indispensable: 1) the molecule is composed of hydrophilic and hydrophobic groups; 2) it acts on the surface. ^[5]

The research and production of food emulsifiers in China started late, and there is a large gap between them in terms of variety and quality. The food emulsifiers approved for use in 1981 are only two varieties, monoglyceride and soybean phospholipid, but the development speed is fast. By 2002, there were 29 kinds of food emulsifiers allowed. At present, there are 49 types of food emulsifiers and food additives with emulsification function allowed in GB 2760-2014 "Food Additives Use Standard", including 2 types of propylene glycol fatty acid esters, 9 types of glycerol fatty acid esters and their derivatives, and polyglycerol. 2 types of fatty acid esters, 12 types of polyhydric alcohol fatty acid esters and their derivatives, 3 types of phospholipids and their derivatives, 6 types of organic acid salts (lactate, stearate, and stearoyl lactate) 8 kinds of alcohols and 6 kinds (modified starches, vegetable gums, soluble soybean polysaccharides, sodium caseinate), and 1 new kind (soap bark extract). 49 kinds of food emulsifiers need to be used within the food classification and maximum usage range specified in GB 2760-2014, of which 12 kinds can be used in various foods according to production needs, including mono- and diglycerin fatty acid esters (CNS 10. 006), citric acid fatty acid glyceride (CNS 10.032), lactic acid fatty acid glyceride (CNS 10.031), acetylated mono- and diglycerin fatty acid ester (CNS 10.027), phospholipids (CNS 04.010) ), Modified soybean phospholipids (CNS 10. 019), enzymatic hydrolyzed soybean phospholipids (CNS 10. 040), hydroxypropyl starch (CNS 20. 014), sodium octenyl succinate starch (CNS 10. 030), glycerol ( CNS 15. 014), sodium caseinate (CNS 10.002). Among them, CNS refers to China Number System. In addition, it can be used in various types of food processing, and there are three types of residues that do not need to be limited, namely mono- and diglycerin fatty acid esters (CNS 10. 006), phospholipids (CNS 04. 010), and glycerol (CNS 15 014). GB 27602014 added 10 new varieties of food additives, including 1 new food emulsifier: quil-laia extract, INS 999 (INS refers to the international number system), allowed daily Acceptable intake (ADI) (allowable intake per kg of body weight per day, mg): 0 to 1 mg (based on rosin saponins per kg). GB 27602014 stipulates that it can be used in foods such as fruit and vegetable juice (slurry) beverages, protein beverages, carbonated beverages, special-purpose beverages and flavored beverages, with a maximum amount of 0.05g / kg. ^[2]

Food emulsifier is a commonly used food additive. The Food Safety Law of the People's Republic of China defines food additives as "adding food for the purpose of improving food quality and color, aroma, taste, and preservation, preservation and processing needs. Artificially synthesized or natural substances ". The use of food additives needs to meet three basic conditions: first, it is really necessary, if it is not needed, it is not added, and it can be added as little as possible; second, it is safe and reliable. Thresholds for the content of harmless additives to humans; the third is to obtain government approval. China's "Standards for the Use of Food Additives (GB2760-2011)" has clear regulations on the scope, variety, and amount of food additives allowed, including emulsification. Details of the agent. Food additives and ingredients use "do not sing praise" as the industry culture, and the society often has a "pinching persimmon" mentality, and after planning "success" in advance, it goes astray. However, media reports also focus on attracting people's attention without factual reporting. In view of this situation, it is necessary to popularize relevant knowledge. ^[5]

The application of emulsifiers in the material synthesis industry is mainly to use it for emulsion polymerization to synthesize coatings, adhesives and other products. Finding high-efficiency emulsion polymerization agents with stable performance and low price is the research and development direction of emulsifiers in this industry. For example, in the synthesis of adhesives, the widespread application of polyacrylate adhesives is due to the polymerization of acrylate emulsion adhesives. The polymer must be dispersed in water under the condition of low molecular weight surfactants, which causes a part of Free emulsifiers remain in the polymer, reducing the adhesion of the emulsion adhesive to the surface of the substrate. In order to solve this problem and effectively prevent migration of the emulsifier after film formation, a polymerizable emulsifier capable of improving water resistance and adhesion of the coating film has been further studied. In addition, in the synthesis of materials, environmentally friendly reactive emulsifiers have been further applied as alternatives to traditional emulsifiers. For example, the emulsifier SR-10 not only has strong emulsifying ability, excellent environmental performance, meets various physical property requirements and has a low starting point. Foaming and other advantages. ^[6]

Emulsifiers are mainly used for the modification of aquaculture feed in the aquaculture industry. In livestock and poultry aquaculture, in order to speed up the growth rate of animals, improve the performance of animals, and reduce the ratio of feed to meat, emulsified oil is commonly used in feed. In this way, the amount of bile salts needed to digest a high proportion of fat exceeds the secretion of livestock and poultry, resulting in indigestion of feed and accumulation of fat in the liver. For this reason, the selection of suitable feed emulsifiers has become the key to the application of emulsifiers in the breeding industry. At present, ionic bile acid salts and lecithin emulsifiers are mostly used in aquaculture of livestock and poultry. The main function of these emulsifiers is to protect liver and gallbladder and regulate meat quality, but its emulsification effect is not ideal. Non-ionic feed emulsifiers can achieve higher emulsifying properties, such as glyceryl monostearate and sucrose fatty acid esters. At the same time, fatty acid enzymes capable of accelerating fat cleavage are increasingly used as additives in feed emulsifiers. ^[6]

Emulsifiers are widely used in cosmetic products and cosmetics in the daily chemical industry. The emulsifiers used include natural surfactants and synthetic surfactants. The former comes from an automatic plant, which is a relatively complex high molecular organic substance, which usually has a high viscosity, is easy to emulsify and stable, has no irritation, and has no toxic and side effects, such as lecithin, cholesterol, lanolin, and tea saponin. The latter is usually a solid particle emulsifier. A thin film is formed on the surface of the dispersed phase droplets to prevent aggregation between the droplets to obtain a stable oil / water dispersed phase. It is mainly used as an anti-allergic formula without chemical emulsifiers and as a sunscreen. Product formula cosmetic additives. ^[6]

In the military industry, emulsifiers are often added to explosives to make emulsion bombs. Generally, a water-insoluble hydrocarbon fuel is used as a continuous phase, and a supersaturated ammonium nitrate solution is used as a dispersed phase. Through the emulsification of the emulsifier, the ammonium nitrate solution is dispersed in the hydrocarbon fuel with extremely small droplets. Special water-in-oil latex system. Since the emulsion explosive is a thermodynamically highly unstable system and an irreversible system, the role of the emulsifier is to greatly reduce the oil-water interfacial tension, and an interface film is formed at the interface to make it difficult to coalesce the ammonium nitrate droplets in the internal phase, thereby improving the stability of the emulsion explosive. ^[6]

In ore flotation, the emulsifier is used to improve the flotation of coal slime, metal ores and non-metal ores. During the flotation process, the degree of emulsification and dispersion of the flotation agent has an important effect on its use efficiency and flotation effect. Therefore, the addition of emulsifiers can help improve the trapping performance of the flotation machine and greatly reduce the flotation agent's performance. consumption. ^[6]

Compared with ordinary diesel oil, micro-emulsified diesel oil prepared by adding emulsifier to a mixed system of water, methanol and diesel oil has better combustion performance, lower energy consumption and less pollution. Adding biodiesel with a certain emulsifying capacity to petrochemical diesel can not only promote the development of the renewable energy industry, reduce emissions, improve the environmental performance of fuel oil, but also facilitate the emulsification of fuel oil, increase the combustion rate, and reduce energy consumption. ^[6]