SURFACTANTS: BASICS AND VERSATILITY IN FOOD INDUSTRIES

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In the Fig.8, the repulsion between the liquid crystal particles and the oil drops are sufficient to prevent aggregation (provide colloidal stability) and they exist as separate entities. If flocculation occurs, three arrangements are possible depending on the magnitude of the interfacial free energies, which are γ(O/W), γ(O/LC) and γ(LC/W) emulsions. The emulsion now has increased the number of phases from two to three, and the presence of the third phase has three vital consequences. It radically changes the volume ratios in the emulsion, it gives rise to another structure during emulsification and the temperature variation during and after the emulsification has decisive effect on the properties.

The most complex colloids and emulsions are those of food and food products, which are difficult to stabilize, because a large number of microstructures of combinations of proteins, carbohydrates, fats and lipids etc. are present. This almost infinite number of combinations are organized and arranged in very complex internal microstructures with various types of assemblies such as dispersions, emulsions, foams, gels, etc. In addition, Mother Nature has provided us with many small molecular weight molecules with surfactants that are known, as food additives (vitamins, antioxidants, acidulants, enzymes, flavors, etc.). The additives have many functional properties and play significant role in food quality and long-term stability17.

3.2 Common Food emulsifiers/surfactants
Surfactant molecules, which are part of these emulsions, play a major role in determining the microstructure of the product and in affecting its structural and textural stability in the food. Commercially utilized common surfactants or food emulsifiers are listed in Table-1. Here in the table, an E-number is a reference number given to food additives that have passed safety test and have been approved for use throughout the European Union and Switzerland (the "E" stands for "Europe"). They are commonly found on food labels throughout the European Union18. Safety assessment and approval are the responsibility of the European Food Safety Authority. Today the worldwide food surfactant production has reached approximately 500,000 tons from 20 different types with a 3% annual growth19. Surprisely about 50% of surfactants are used in bakery products.

Table-1: Most common food surfactants/emulsifiers used in the food industries.

Name of Food surfactant/Emulsifier

Code name

E-Number

Lecithins

Lecithins

E 322

Polyoxyethylene sorbitan esters

Polysorbates/Tweens

E 432 – 436

Mono- and diglycerides of fatty acids

MDG/ Monoglycerides

E 471

Acetic acid esters of MDG

ACETEM

E 472 a

Lactic acid esters of MDG

LACTEM

E 472 b

Citric acid esters of MDG

CITREM

E 472 c

Mono- and diacetyl tartaric acid esters of MDG

DATEM

E 472 e

Sucrose esters of fatty acids

Sucrose esters

E 473

Polyglycerol esters of fatty acids

Polyglycerol esters

E 475

Polyglycerol polyricinoleate

PGPR

E 476

Propane-1,2-diol esters of fatty acids

Propylene glycol esters

E 477

Sodium stearoyl-2-lactylate

SSL

E 481

Calcium stearoyl-2-lactylate

CSL

E 482

Sorbitan fatty acid esters

Spans

E 491 – 495

The chemical structure of commercial food emulsifiers is represented in Table-2. In most cases, the hydrophilic part is of glycerol, sorbitol, sucrose, propylene glycol or polyglycerol and lipophilic, hydrophobic part is formed by fatty acids derived from fats and oils.

Table-2 : Chemical structure of MOST common food Surfactants/ emulsifiers used in the food industries.

3.3. Manufacture of Food emulsifiers/surfactants
Lecithin (E322) is a mixture of phospholipids, it consists of a glycerol backbone with phosphatidyl groups. The phosphatidyl groups are phosphate esters of diglyceride. Lecithin is a natural emulsifier, obtained mainly from vegetable oilseeds and egg yolk.

Basic source for manufacture of food emulsifiers is actually come out from fats or oils or fatty acids. Main food emulsifiers, monoglycerides are produced with the reaction of fats or oils or fatty acids with glycerol. Such monoglycerides can be further processed by esterification with organic acids like acetic acid, lactic acid, citric acid and tartaric acid, produces ACETAM, LACTEM, CITREM as well as DATEM, respectively. Even some important hydrophilic alcohols can be used for the manufacturing of food emulsifiers (shown in Fig.9).

Fig.9 : Source and manufacturing of Food emulsifiers/surfactants

3.4. Few applications of Food emulsifiers/surfactants in Food industries.
Surfactants are involved in the production of many common food items and can be found in the extraction of cholesterol, solubiliztion of oils, liquor emulsification, prevention of component separation, and solubiliztion of essential nutrients.

The nontoxicity of lecithin leads to its variety of uses in food, as an additive or emulsifier. In confectionery, lecithin reduces viscosity, replaces more expensive ingredients, controls sugar solidification and the flowness properties of chocolate, helps in the homogeneous mixing and it can be used as a coating. In emulsions and fat spreads, it stabilizes emulsions, reduces spattering during frying, and improves texture of spreads and flavour release. In dough’s and bakery, it reduces fat and egg requirements, helps even distribution of ingredients in dough, stabilizes fermentation, increases volume, protects yeast cells in dough when frozen, and acts as a releasing agent to prevent sticking and simplify cleaning. It improves wetting properties of hydrophilic powders (e.g., low-fat proteins) and lipophilic powders (e.g., cocoa powder), controls dust, and helps complete dispersion in water to adsorb at interfaces. Lecithin keeps cocoa and cocoa butter in a candy bar from separating. In margarines, especially those containing high levels of fat (>75%), lecithin is added as an 'antispattering' agent for shallow frying. Margarine is an example of a W/O emulsion which consisting of 80% fat, the hot homogenized mixture of fat crystals, oil and water. It does not have to be a stabile emulsion since the emulsion is quickly set by rapid chilling. Lecithin, a typical ingredient in margarine, enhances the solubility of monoglycerides in the oil blend, and monoglycerides reduce the interfacial tension between the oil and water phases.

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