|Frost & Sullivan Market Insight||Published: 21 Feb 2002|
by Ivan Fernandez
In the early 1960s, when British researcher Alec D. Bangham identified microscopic spherical vesicles, formed when phospholipids were mixed with water, he helped bring to life a whole new delivery system that found eager early adopters in the pharmaceutical industry. Liposomes - the microscopic spherical vesicles with a bi-layered membrane of lecithin molecules - have since been used as delivery systems for drugs (notably in cancer therapy), vaccines, insulin, blood substitutes, imaging agents, and in the study of the effects of pathogens, drugs, vitamins, and hormones. More recently, liposomes are being studied for their application in gene therapies.
Apart from pharmaceutical applications, liposomes also find application in the controlled release of active ingredients in the plastics, pesticides, paints, and cosmetics industries. The cosmetics industry, for instance, relies on liposomes for their excellent moisturizing and nutritional effects on the skin. But, when it comes to applications in the food industry, liposomes have for long been found wanting because of their instability, low volumes in production, and high cost of equipment and production.
Fortunately for food processors, advanced formulation and processing technologies have now increased the stability of liposomes. Also, new techniques for the production of liposomes have made possible the use of regular lecithins, instead of the far more expensive specialized forms of lecithin used earlier.
Lecithins - a naturally occurring group of phospholipids that are building blocks for cellular membrane - are ideal for the production of liposomes because they have both polar and nonpolar symmetry on the same molecule (the amphiphilic molecule). That is why, lecithins can be hydrophobic (water-resisting) on one side and hydrophilic (water-attracting) on the other. In terms of structure, liposomes can be either unilamella (one bilayer) or multilamella. They measure anywhere between 20 nanometers and 1,000 nanometers (1 micron).
Liposomes as Food Ingredient Vectors: The Advantages
The advantages of liposomes, which made them effective drug-delivery systems and are now making them food-ingredient-delivery systems, are:
Food Ingredient Applications
For the food and beverage industry, liposomes can perform the functions of protecting active ingredients, retaining water, controlling the release of active ingredients based on temperature, pH, oxidation rate, aqueous state, etc., controlling crystallization, reducing the loss of inherent properties of ingredients due to processing, and retaining flavour.
Functional Food Ingredients:
Perhaps the most exciting potential for the application of liposomes is seen in the high-growth area of nutraceuticals, where liposomes can provide controlled release of nutritional and therapeutic ingredients. Liposome encapsulation ensures that vitamins, minerals, herbal extracts, or hormones, are protected and delivered with greater stability and maximum effect. Their use will leverage the strengths of functional food ingredients better, especially of those that have low bioavailability or solubility.
Flavours and Fragrances:
Fine-tuning the composition and temperature-sensitivity of the liposome, as well as the permeability or degradation rate of the membrane, can release flavours in the mouth that can maximize food taste and extend the appeal of the consumption experience. Specialized applications of liposomes could be in the manufacture of flavoured lozenges and fresh-breath mints, and in flavour retention for reduced-fat foods. Liposomes can also facilitate the fresh release of aroma and flavour when food is reheated. This could find widespread application in heat-and-serve foods. For baked foods such as cakes and cookies, liposomes are proving useful in encapsulating flavours, fragrances, antioxidants and preservatives.
Liposomes have been found to improve the efficacy of enzymes in shortening the fermentation period for cheese and beer. Using liposome-encapsulated enzymes for accelerating the ripening of cheese, can also minimize bitterness and curtail the loss of yield. Since liposomes can be prepared with varied size, load, pH, and temperature-sensitivity combinations, they lend themselves well to the ripening of a wide variety of cheese. Experiments on liposome-entrapped enzymes are also working toward extending shelf-life of different products by retarding spoilage due to microbial action.
Toward Widespread Commercialization
Liposomes' diagnostic imaging application, in the field of medicine, may now find great utility in food safety inspection procedures for the identification and analysis of food-borne pathogens. But the widespread incorporation of liposome technology, as part of smarter processing practices, will take a while longer. Food manufacturers and processors are hoping that further research and development will make liposome delivery systems viable propositions, both technologically and commercially. The challenge will be to increase the stability of liposomes so that they withstand fluctuations in temperature, pressure, aqueous state, pH, etc that are not only part of food processing but also part of consumption. Production techniques will also have to improve efficiencies in terms of the volumes and uniformity of liposomes produced, and the rate of encapsulation of the desired ingredient.
Most eyes will be turned to the functional food industry and its adoption of this technology, eventually. This apart, by virtue of their ability to improve the effectiveness of active ingredients, liposomes could herald the more judicious use of colours, flavours, fragrances, and other additives. For consumers who are turning increasingly suspicious of most additives, this will certainly be good news. And for food manufacturers, this improved targeting and increased effectiveness could lead to resource conservation and greater savings.