1. A food emulsifier is a surface-active agent. It acts as a border between two immiscible liquids like oil and water and allows them to be blended into stable emulsions. It is also known as an emulgent. Emulsifiers control crystallization, reduce stickiness and also prevent separation.
2. The emulsifiers work by forming physical barriers. These physical barriers keep droplets from coalescing. Emulsifiers contain both hydrophilic (water-loving or polar) head group and hydrophobic (oil-loving, non-polar) tail group. Since it contains both water-loving and oil-loving head and tail group respectively, it is attracted to both polar and non-polar compounds. When emulsifiers are added to an oil-water emulsion, they surround the oil droplet with their non-polar tails extending into the oil and their polar head groups facing the water. The reverse happens in the water-oil emulsion. The non-polar tails extend outward into the oil phase and the polar head groups point to the water droplet. Thus, the emulsifiers lower the interfacial tension between the oil and water phases. It stabilises the droplets and prevents them from coalescing.
Emulsifiers can be positively charged, polar head group, negatively charged head group or uncharged head group i.e. it can be cationic, anionic and non-ionic too. When the charged emulsifiers coat droplets in an oil-water emulsion, the positive or negative charges on the outside of the oil droplets repel each other electrostatically, the helping to keep the droplets separated.
Non-ionic emulsifiers have large, bulky head groups that point away from the oil droplet. These polar head groups clash and even tangle with head groups on other water droplets, thus hindering the droplets from coming together.
According to the application, emulsifiers are used. Cationic emulsifiers are used in low to neutral pH solutions. Anionic emulsifiers are used in alkaline solutions. Non-ionic emulsifiers can be used alone or they can be combined with charged emulsifiers to increase emulsion stability.
3. The common emulsifiers include mustard, soy and egg lecithin, mono and diglycerides, glycerides, monoglyceride derivates, polysorbates, carrageenan, guar gum, canola oil, fatty acid derivates, proteins, sodium stearoyl lactylate, ammonium phosphatide, locust bean gum, xanthan gum etc.
4. Two types of emulsions are created by emulsifiers-
i) droplets of oil dispersed in water
ii) droplets of water dispersed in oil
There is a continuous and dispersed phase within the emulsion. The continuous phase is the water and the dispersed phase is the oil in an oil-in-water-emulsion. In a water-in-oil-emulsion, the oil is the continuous phase.
By applying mechanical force from a blender or a homogenizer, emulsions can be made. This force breaks down the dispersed phase into tiny droplets that become suspended in the continuous phase.
One of the most powerful and oldest forms of an animal-derived emulsifier is Lecithin in egg yolks. It is used to stabilize oil in water emulsions, for example, in mayonnaise and hollandaise sauce.
5. Emulsifiers are used in our food products for a number of reasons.
i) They make the food appealing to us. For example, mayonnaise without the emulsifier would be so unappealing if oil and water separated before it's even used.
ii) Emulsifiers have a huge effect on the structure and texture of many foods. They are used to help in the processing of foods and also to help maintain the quality and freshness of foods.
iii) Emulsifiers help in preventing the growth of moulds in low fat spreads, which would happen if oil and fat are separated.
iv) Some emulsifiers like lecithin are very good for the body. Lecithin can reduce the high level of cholesterol, blood pressure. It also helps in the treatment of Alzheimer's disease.
6. It is important to know about various emulsifiers to recognize them in the ingredients list of the food product. Also, laboratory tests can be done to find out the type of emulsifier used in a food product.
Hope it helps.
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