Lipids emulsification

ATP-dependent process, aided by the bile-salt excretion pump (BSEP) expression in the canalicular membrane. Conjugation increases the aqueous solubility of the bile adds, and renders these bile adds largely impermeable to the cell membranes of the intestine and duodenum hence, they are unable to leave the intestinal lumen. This allows bile-add levels to rise in the lumen, ultimately reaching sufficient concentrations to form micelles, which allow lipid emulsification and subsequent absorption. 

As discussed in Section 19.3.5.3, mimicking human digestion for the assessment of Se-bioavailability could be practically regarded as early examples of sequential enzymatic sample preparation applying, for example, proteolytic (pepsin), mixed (pancreatin), and non-proteolytic (amylase) enzymes, and digestive compounds like bile salts for lipid emulsification. On the other hand, the simultaneous use of enzymes was not considered a source of self-digestion problems as this phenomenon is common in the digestive tract. 

Dietary fats, libers, and other carotenoids have been reported to interfere with carotenoid bioaccessibility. It is clear that by their presence in the gut, lipids create an environment in favor of hydrophobic compounds such as carotenoids. When arriving in the small intestinal lumen, dietary fats stimulate bile flow from the gallbladder and therefore enhance the micelle formation, which in turn could facilitate the emulsification of carotenoids into lipid micelles. Without micelle formation, carotenoids are poorly absorbed a minimum of 3 g of fat in meal is necessary for an efficient absorption of carotenoids, except for lutein esters that require higher amounts of fat. ... 

Emulsification breaks lipid droplets into smaller-sized structures, which increases their overall surface area. 

Trotta M., Debernardi R, and Caputo O., Preparation of solid lipid nanoparticles by a solvent emulsification-diffusion technique, Int. J. Pham., 251, 153, 2003. 

Spontaneous emulsification and solvent diffusion method Solid lipid nanoparticles 20-80 nm Horn and Rieger, 2001 Cui et al., 2006 Ribeiro et al., 2008... 

The following factors appear to control the emulsification properties of milk proteins in food product applications 1) the physico-chemical state of the proteins as influenced by pH, Ca and other polyvalent ions, denaturation, aggregation, enzyme modification, and conditions used to produce the emulsion 2) composition and processing conditions with respect to lipid-protein ratio, chemical emulsifiers, physical state of the fat phase, ionic activities, pH, and viscosity of the dispersion phase surrounding the fat globules and 3) the sequence and process for incorporating the respective components of the emulsion and for forming the emulsion. 

To remove lipids, sample extracts are frequently also partitioned with n-hexane (25, 33-35, 37, 40, 43, 45, 47, 49, 50, 53-57, 62), petroleum ether (31, 38, 63), isooctane (36, 41, 48), or toluene (26, 58, 59, 61). Use of n-toluene is not recommended, however, in chloramphenicol and florfenicol analysis, because these drugs have the tendency to transfer into toluene to some extent during the partitioning process. As an alternative to the classic liquid-liquid partitioning cleanup, some workers in the field (24, 26, 34, 58, 59) have suggested use of diatomaceous earth columns as another option of a liquid-liquid partitioning process that offers substantial reduction in emulsification problems and, thus, allows a high recovery increase. 

Calomel electrodes are used, connected to the water phase on both sides of the black lipid film by KCl-containing capillaries. The water phase is generally 0.25M KC1, which precludes interface contamination by spontaneous emulsification. Carbon tetrachloride is used as the undermost oil layer, which serves exclusively as an electric seal. 

The critical process of emulsification of dietary lipids occurs in the duodenum. Emulsification increases the surface area of the hydrophobic lipid droplets so that the digestive enzymes, which... 

Edmondson et al (1971), who studied the enrichment of whole milk with iron, found that ferrous compounds normally caused a definite oxidized flavor when added before pasteurization. Aeration before addition of the iron reduced the off-flavor. The authors recommended the addition of ferric ammonium citrate followed by pasteurization at 81 °C. Kurtz et al. (1973) reported that iron salts can be added in amounts equivalent to 20 mg iron per liter of skim milk with no adverse flavor effects when iron-fortified dry milk is reconstituted to skim milk or used in the preparation of 2% milk. Hegenauer et al. (1979A) reported that emulsification of milk fat prior to fortification greatly reduced lipid peroxidation by all metal complexes. These researchers (Hegenauer et al. 1979B) concluded that chelated iron and copper should be added after homogenization but before pasteurization by a high-temperature-short-time process. 

Prepare a liposome suspension, containing MPB—PE, at a total lipid concentration of 5 mg/ml in 0.05 M sodium phosphate, 0.15 M NaCl, pH 7.2. Activation of DPPE with SMPB is described in Section 2. A suggested lipid composition for vesicle formation is PC cholesterol PG MPB—PE mixed at a molar ratio of 8 10 1 1. The presence of relatively high levels of cholesterol in the liposomal recipe dramatically enhances the conjugation efficiency of the component MPB—PE groups (Martin et al., 1990). Any method of emulsification to create liposomes of the desired size and morphology may be used (Section 1). 

One of the major drawbacks of liposomes is related to their preparation methods [3,4]. Liposomes for topical delivery are prepared by the same classic methods widely described in the literature for preparation of these vesicles. The majority of the liposome preparation methods are complicated multistep processes. These methods include hydration of a dry lipid film, emulsification, reverse phase evaporation, freeze thaw processes, and solvent injection. Liposome preparation is followed by homogenization and separation of unentrapped drug by centrifugation, gel filtration, or dialysis. These techniques suffer from one or more drawbacks such as the use of solvents (sometimes pharmaceutically unacceptable), an additional sizing process to control the size distribution of final products (sonication, extrusion), multiple-step entrapment procedure for preparing drug-containing liposomes, and the need for special equipment. 

Emulsions and suspensions are colloidal dispersions of two or more immiscible phases in which one phase (disperse or internal phase) is dispersed as droplets or particles into another phase (continuous or dispersant phase). Therefore, various types of colloidal systems can be obtained. For example, oil/water and water /oil single emulsions can be prepared, as well as so-called multiple emulsions, which involve the preliminary emulsification of two phases (e.g., w/o or o/w), followed by secondary emulsification into a third phase leading to a three-phase mixture, such as w/o/w or o/w/o. Suspensions where a solid phase is dispersed into a liquid phase can also be obtained. In this case, solid particles can be (i) microspheres, for example, spherical particles composed of various natural and synthetic materials with diameters in the micrometer range solid lipid microspheres, albumin microspheres, polymer microspheres and (ii) capsules, for example, small, coated particles loaded with a solid, a liquid, a solid-liquid dispersion or solid-gas dispersion. Aerosols, where the internal phase is constituted by a solid or a liquid phase dispersed in air as a continuous phase, represent another type of colloidal system. 

Bile salts are substances derived from sterols, which make up a substantial part of the solid matter in bile and which play a central role in lipid absorption, by virtue of their surface-active properties. The structure and properties of these salts have been reviewed by Haslewood (305) and Heaton (316). Bile salts essentially have molecules of detergent type hydrocarbon, with a fat-dissolving part and a polar, water-attracting part. The fat-dissolving part consists of the bulk of the steroid nucleus. The hydroxyl groups are so distributed that hydration can readily take place the remainder of the molecule will dissolve the fatty phase. Emulsification of fat/water complexes can thus occur easily. The terms bile acid and bile salt are used somewhat interchangeably in the literature. 

On the basis of the experience accrued so far, the extraction efficiency can be affected by both the nature of the sample under test and the As species actually present in the sample. The lipid content of the sample and the presence of As species with hydrophobic residues play a key role in this context. As a consequence, it may be useful to remove or partition lipids with an organic solvent prior to the methanol-water extraction in order to increase the extraction efficiency. This approach is also viable to prevent emulsification of methanol and lipids, which could otherwise significantly reduce the extraction efficiency [26]. Thus, sample preparation prior to As speciation usually starts with the chloroform-methanol extraction, followed by centrifugation of the sample solution to remove solid particles. Subsequently, after the addition of methanol and water, the supernatant is separated in a funnel. The amount of As remaining in the organic phase is usually quantified as total As by wet digestion after solvent evaporation. Obviously, this entails the loss of all speciation information related to the lipid-soluble As species [2]. Speciation analysis is finally carried out on the methanol-water phase, usually after solvent evaporation (see Table 19.2). 

Since lipases act on lipids at lipid-water interfaces, preparation of substrates in a suitable physical form for maximal lipase activity is very important. Preparation methods include emulsification with an emulsifying agent incorporation into a gel dissolution in a water-soluble organic solvent, such as 2-methoxyethanol or tetrahydrofuran, followed by addition to an aqueous reaction mixture sonication, with or without emulsifier and formation of a thin film or monolayer. 

Polymeric micelles Poloxamer-like block copolymers PEG and lipophilic polymer copolymers PEGylated lipids Dialysis, emulsification, or film method 35,36... 

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