The tendency of products such as ice cream, chocolate, milk, cakes, etc. containing oil, water, or even gas in some cases as their components tend to separate and in such cases lead to non-uniformity. Food product development has evolved over the years to cater for such products also known as emulsions with chemical substances known as emulsifiers.
Emulsions are normally defined as heterogeneous systems of two immiscible layers, one liquid dispersed throughout another in the form of droplets usually exceeding 0.1 μ m in diameter Emulsions are usually categorized into single emulsions which include water-in-oil and oil-in-water and multiple emulsions including water-in-oil-in-water and oil-in-water-in-oil. The food industries have since then provided the consuming public with emulsified products that have been well preserved and are friendly to one’s health and safety.
Consumers in recent times, at their convenience and discretion, will be able to buy these products at any time they desire. These developments have not been a smooth ride to achieve and in many instances have required special processing or preservation techniques using various food emulsifiers which sometimes act as preservatives to permit foods to be of high quality, convenient, as well as have a longer shelf-life, easier storage modes and to be appealing to the five sense organs. Food emulsifiers form a facet of additives that have been increasingly used by the food industry to provide these qualities.
Emulsions when made are usually characterized by destabilizations such as flocculation, creaming, and coalescence which affects the products in terms of decreased shelf life and non-uniformity, thus the need for emulsifiers. Despite being used interchangeably with other terminologies such as surfactant, surface-active agents, etc. The term emulsifiers generally refers to chemicals that are capable of promoting the stabilization of emulsions or foams by interfacial action or increasing the kinetic energy. The first category of food emulsifiers utilized in the food industry were natural substances which include gums, lecithin, polysaccharides, etc. While these materials were significant breakthroughs in their day, they were insufficient in meeting the diverse requirements of an industry that is on an adventure to satisfy growing demands for sophisticated and highly formulated foods(Babu and Gowda, 2013).
One of the most common types of emulsifying is egg yolk. Despite eggs being consumed wholly as food, be it boiled or fried, their yolk plays a vital role in stabilizing some common food products such as cakes, and ice-creams as well as increasing their shelf life. Egg yolk contains the secret ingredient egg lecithin, a substance that is rich in phospholipids, particularly phosphatidylcholine. Lecithin is a compound that occurs naturally in various foods, and it serves as an emulsifier, helping to mix and stabilize oil and water-based ingredients. Egg lecithin is often extracted from egg yolks through techniques such as centrifugation or solvent extraction process by separating the lecithin from other components of the yolk. In most home bakeries, the yolk is beaten and added to the formulated cake recipe since it contains the binding agent lecithin. Egg lecithin is valued for its emulsifying properties, making it a common ingredient in the food industry. It is used in various culinary applications, such as in baking to improve the texture of the dough, in the production of mayonnaise to stabilize the mixture of oil and water, and in the creation of creamy sauces and dressings(Shen et al., 2020).
Egg lecithin plays an important role in improving shelf life and stabilizing emulsions due to its unique chemical properties, which are centered on the presence of phospholipids, with phosphatidylcholine being a major component. The amphiphilic nature of egg lecithin allows it to attract both water and fat, making it hydrophilic and lipophilic respectively. This dual nature allows lecithin to act as a bridge between water and fat, thereby ensuring the formation and stabilization of emulsions. In scenarios such as salad dressings or mayonnaise, egg lecithin surrounds and encapsulates fat droplets, preventing them from coalescing (emulsion destabilization) or separating from the water phase. This leads to a stable and uniform mixture. The antioxidant properties of the phospholipids contained in the lecithin helps to inhibit the oxidation of fats in food products, preventing rancidity and extending the shelf life of products that contain fats(Palacios and Wang, 2005).
Although advancements in food science have led to the development of egg substitutes and synthetic emulsifiers for those who require alternatives to traditional egg yolk. It is worth knowing that eggs have natural preservative properties due to the presence of lecithin contained in the egg yolk. There are other alternative sources of lecithin, such as soy lecithin or sunflower lecithin, that are often used in food production. These alternatives are best for individuals with dietary restrictions.
References
Babu, U.V. and Gowda, D.V.S. (2013) ‘Emulsions and emulsifiers’, The Asian Journal of Experimental Chemistry, 8(1&2), pp. 30–45.
Palacios, L.E. and Wang, T. (2005) ‘Egg-yolk lipid fractionation and lecithin characterization’, JAOCS, Journal of the American Oil Chemists’ Society, 82(8), pp. 571–578. Available at: https://doi.org/10.1007/s11746-005-1111-4.
Shen, Y. et al. (2020) ‘Interactions between lecithin and yolk granule and their influence on the emulsifying properties’, Food Hydrocolloids, 101, p. 105510. Available at: https://doi.org/10.1016/j.foodhyd.2019.105510.
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