Coatings lecithin applications

Solid particle dispersions (Sols). Many lecithin products are still the best and most effective surfactants for dispersing sols. This seems to be because of lecithin s affinity for solids—liquid surface interfaces. Phospholipids seem particularly attracted to particles containing metals and metal salts. Examples of food sols include some liquid chocolates, instant drinks, frosting mixes, pigmented foods, and others. The nonfood applications include paints, inks, and other pigmented coatings. 

Lecithins can be dissolved in oil, dispersed in water, or used as is, in release applications. Oil-free lecithins can be dry blended into breading, coatings, and spice or seasoning mixes for release of the coated food product from the food-contact surface. In food products that have a high surface area-to-volume ratio, like pancakes or fortune cookies, lecithin can be added directly to the product formulation to achieve release from the cooking/baking surface. Effective release depends on... 

Instant foods. Lecithin has been used as a wetting agent and emulsifier in instant foods. Foods including cocoa powder, instant drinks, instant cocoa and flavored coffee, powdered protein drinks, coffee whiteners, instant puddings, cake mixes, and instant toppings are widely employed applications for specific lecithins. The most common method to incorporate lecithin is as an external coating on the powder particles. The particular lecithin to be employed largely depends on the hydrophilicity or lipophilicity of the powder system (7). 

Lecithin has some catalytic or cocatalytic effects in multiphase systems because of its surface-active properties. Lecithin is reported to be useful as an emulsifier in the curing of aqueous dispersions of unsaturated polyesters (337). The products are more easily removed from their molds and have improved mechanical properties when lecithin is used. In a fermentation application, 1.5% soybean lecithin acts as an inducer in the preparation of cholesterol esterase using a strain of Pseudomonas bacteria (338). Aside from its role as a catalyst, initiator, or modifier, lecithin may have ancillary uses in catalyst systems as part of a protective coating (339). 

The literature is replete with information on special lecithin products in coating applications (56). Various formulations have been published, and special lecithin blends patented, for improved functionality in specific areas. Examples of these... 

Coating organic polymer films with lecithin can improve the release properties of the film from the crimp jaws of the automated packaging machine (441). In analytical equipment, lecithin is used to improve the wettability of the contact surface, which enables the solvent to be presented uniformly for analysis (442). Incorporation of lecithin in a masking application can reduce bubble formation and improve the uniformity of the apphcation (443). And finally, lecithin can be used as a protective coating for a painted surface such as found on automobiles. Once applied, it facilitates the removal of insects and debris. The coating is resistant to rain and washing away (444). 

An interesting coatings application for lecithin is in producing nonpyrophoric Raney nickel (339). The lecithin in this application creates a lipophilic surface on the metal, along with a wax, fat, or organic polymer. 

For the most part, the greatest percentage of lecithin is used in foods. The second highest use is in animal feeds, followed by industrial applications. Paints and other coatings consume a major portion of the nonfood lecithin. Pharmaceuticals, including dietary supplements, and inks and cosmetics, however, also consume significant portions. 

Highly oxidizable oils such as fish oils can be protected by a process known as microencapsulation, which coats the oil with a matrix of protein (gelatin, casein), carbohydrates (starch, cellulose, carboxymethylcellulose or cellulose derivatives) and lecithin. Microencapsulation provides protection against oxidation and imparts oxidative stability. The use of carboxymethylcellulose and cyclodextrins as coatings is claimed to provide better protection of oils by improved oxygen barrier properties. For special applications as nutritional supplements, fish oils enriched in n-3 PUFA are microencapsulated, in the presence of antioxidants, into a powder that is relatively stable at ambient temperatures. However, encapsulated fish oils can impart undesirable fishy taste when incorporated into food emulsions. More research and development is needed to evaluate potential applications and benefits of active packaging to increase the shelf life of fish oils and other highly oxidizable oils in foods. 

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