Lecithins liposome encapsulation

Liposomes have been successfully used to deliver a range of oil-soluble bioactives. Banville et al. (2000) showed that incorporation of Vitamin D in cheese was improved with liposomal delivery compared to the use of a water-soluble preparation, but after long term storage (3-5 months) the stability of the liposome-encapsulated vitamin decreased. Multilamellar liposomes made from soy lecithin will incorporate P-carotene. Using a lecithin to P-carotene ratio of 1 0.05, efficiencies of up to 99.7% were obtained (Rhim et al. 2000). 

Ferrous sulphate eneapsulated in soy lecithin liposomes has been used to deliver iron. These preparations have improved bioavailability compared to ferrous sulphate directly added in milk and dairy products (Boccio et al. 1997 Uicich et al. 1999). Albaldawi et al. (2005) reported that the addition of encapsulated haem iron in lecithin/cholesterol liposomes resulted in improved rheological properties of bread dough and the sensory properties of baked bread. 

The term encapsulation has been used to distinguish entrapment preparations in which the biocatalyst environment is comparable to that of the bulk phase and where there is no covalent attachment of the protein to the containment medium (Fig. 6-1 D)[21J. Enzymes or whole cells may be encapsulated within the interior of a microscopic semi-permeable membranes (microencapsulation) or within the interior of macroscopic hollow-fiber membranes. Liposome encapsulation, a common microscopic encapsulation technique, involves the containment of an enzyme within the interior of a spherical surfactant bilayer, usually based on a phospholipid such as lecithin. The dimensions and shape of the liposome are variable and may consist of multiple amphiphile layers. Processes in which microscopic compart-mentalization (cf. living cells) such as multienzyme systems, charge transfer systems, or processes that require a gradient in concentration have employed liposome encapsulation. This method of immobilization is also commonly used for the delivery of therapeutic proteins. 

The bioflavor compounds of blue cheese, obtained from fermentation of Aspergillus spp., were encapsulated in soy lecithin liposomes and spray-dried to obtain the powder form by Santana et al. (2005). A sensory evaluation was performed, by adding the liposome-bioflavor powder in a base of light cream cheese, which was spread on toasts. Flavor intensity, acceptance by the consumers, and purchasing intention were the tests done in the sensory evaluation. The results showed that the encapsulation maintained the characteristic flavor of blue cheese and the product was classified by the consumers as acceptable. The dried liposome-stabilized flavor was useful to add in foods and to be kept in storage. 

Liposomes composed of phosphatidylcholine, cholesterol, and dl-(-tocopherol improved shelf life of vitamin C from a few days up to 2 months, especially in the presence of common food components which normally speed up decomposition, such as copper ions, ascorbate oxidase, and lysine (Kirby et al 1991). Calcium lactate was also encapsulated in lecithin liposomes, in this case to prevent undesirable calcium-protein interactions (Champagne and Fustier, 2007). The liposomal calcium levels of fortified soymilk were equivalent to those found in cow s milk. A synergistic effect of coencapsulation of vitamins A and D in liposomes promoted calcium absorption in the GI tract (Champagne and Fustier, 2007). 

Takahashi, M., Inafuku, K., MiyaggT., Oku, H., Wada, K., Imura,T. and Kitamoto, D. (2007). Efficient preparation of liposomes encapsulating food materials using lecithins by a mechanochemical method. Journal of Oleo Science, 56(1), 35-42. 

The correct ratio of lipid constituents is important to form stable liposomes. For instance, a reliable liposomal composition for encapsulating aqueous substances may contain molar ratios of lecithin cholesterol negatively charged phospholipid (e.g., phosphatidyl glycerol (PG)) of 0.9 1 0.1. A composition that is typical when an activated phosphatidylethanolamine (PE) derivative is included may contain molar ratios of phosphatidylcholine (PC) cholesterol PG derivatized PE of 8 10 1 1. Another typical composition using a maleimide derivative of PE without PG is PC male-imide-PE cholesterol of 85 15 50 (Friede et al., 1993). In general, to maintain membrane stability, the PE derivative should not exceed a concentration ratio of about l-10mol PE per lOOmol of total lipid. 

Liposomes in which lecithin is included as a component of the bilayer have been used to encapsulate drug substances their potential as novel delivery systems has been investigated. This application generally requires purified lecithins combined in specific proportions. 

The stmeturai units of liposomes are ainphiphile molecules, mainly phospholipids. Alec Bangham and co-workers observed self-closed lipid structures after they had been dissolved in water [35]. This first observation took place after egg yolk lecithin had been dispersed in water. According to D.D.Lasic and D. Papahadjopoulos, liposomes are self-assembling colloidal particles in which a lipid bilayer encapsulates a fraction of the surrounding medium [36]. 

Nanoliposomes compared to liposomes provide more surface area and have the potential to increase solubility, enhance bioavailability, and improve controlled release. The principal constituents of nanoliposomes are phospholipids for example, soya, rapeseed, and marine lecithin used by Zhang et al. (2012b). Jimenez et al. (2014) incorporated antimicrobial volatile compounds (orange EO and limonene) into soy and rapeseed nanoliposomes. These were then added to starch sodium caseinate film, forming dispersions. The antimicrobial activity of these films was not observed probably due to the encapsulation, which made difficult their release from the matrix (Jimenez et al., 2014). 

Fig. 3. Spontaneous release of carboxyfluorescein (200 mM) encapsulated in the interior core of liposomes with and without artificial cell wall as a function of time at 50 C and y = 0.20 M (NaCl) in 20 mM Tris-HCl (pH 8.6) top, small single-walled liposomes (30 mg, 2.4 x 10" M as lecithin in the cuvette) without polysaccharides ( —O- ) and as coated with 5 mg of OPP-50(5.6) ( ), OPP-50(1.8)...

Liposomes can store water-soluble substances in the core of the bilayer membrane. This has two useful effects. First, distribution of the encapsulated substances in the food is far more homogeneous than is possible with classical emulsifiers. Second, the encapsulated substances are immobiUzed because of the liposomes stability. They do not migrate, and it takes a long time to release them from the product. This means, for example, that a lemon-flavored cake stays fresh longer and tastes of lemon for a longer time too. Nowadays it is possible to produce liposomes in most of the homogenizers used in the food industry if the right fraction of lecithin is used. It is possible to form membrane-like shuctures that can withstand many mechanical and thermal loads. 

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