Sorption of lipids

Studies have demonstrated that the degree of lipid absorption depends on the lipophilicity of the polymer (17). Enhanced lipid absorption was observed in block copolymers in which the lipid polar and hydrocarbon segments associated simultaneously with hydrophilic and lipophilic polymer chain regions, respectively. These results are supported by studies that have demonstrated the sorption of lipids by acrylic hydrogels to be inversely proportional to the hydrophilicity of the polymer (18). 

In Vitro Analytical Results. In vitro studies showed that Biomer and a series of other elastomers underwent sorption of lipid species from a synthetic plasma solution (Figure 1). The 20-week in vitro study on the elastomers showed that rapid sample weight gains occurred in the first 2 weeks... 

Historically, organic environmental pollutants were hydrophobic, often persistent, neutral compounds. As a consequence, these substances were readily sorbed by particles and soluble in lipids. In modern times, efforts have been made to make xenobiotics more hydrophilic - often by including ionisable substituents. Presumably, these functional groups would render the compound less bioaccumulative. In particular, many pesticides and pharmaceuticals contain acidic or basic functions. However, studies on the fate and effect of organic environmental pollutants focus mainly on the neutral species [1], In the past, uptake into cells and sorption to biological membranes were often assumed to be only dependent on the neutral species. More recent studies that are reviewed in this chapter show that the ionic organic species play a role both for toxic effects and sorption of compounds to membranes. 

Additives to starch exert varying effects on the kinetics of water sorption. For example, lipids do not significantly affect the content of adsorbed water. The mode of starch defatting can also influence moisture sorption by molecules of the defatting solvent occupying active centers of sorption.389 The addition of either sucrose or lipids to starch has the same effect on both branches of the hysteresis curve.386,398 Some additives, such as dimethyl sulfoxide or ammonium rhodanide, induce selectivity of the adsorption and solvation of starch 411 Sulfur dioxide accelerates water sorption regardless of the temperature.412 Pretreatment of starch with sulfur dioxide usually increases the water sorption.413 Studies on the sorption of components of water-alcohol mixtures are discussed in Section IV. 

For such starchy foods as noodles, cakes, pastries, processed potato food, and puddings, lipids improve the texture. The tendency of bread to staling is also related to the presence of lipids and emulsifiers. In order to satisfy market demands, it is important to optimize the water-binding capacity, the rate of water sorption, and the swelling power. The effects of lipids on these properties is under ongoing study. The mode of application of lipids is also a factor which controls functional properties.851-853 869 The effect of all these factors on bread quality has been recognized.870-873... 

The formation of inclusion complexes of lipids inside the amylose helix is not the only important factor regulating the functional properties of foodstuffs. The adsorption of lipids on starch surfaces can prevent the separation of components in frozen starch noodles. Such surface sorption reduces the viscosity and adhesiveness of the starch.888 The latter property can also be important in the microencapsulation of medicines. For example, a complex of cornstarch with glucolipids has been patented as an excipient for 3-(p-chlorobenzyl)-6-methoxy-2-methylindole-l-acetic acid.889... 

Magnesium silicate is used against juvenile and adult store product pests, exerting its lethal activity predominantly on juvenile and adult forms by sorption of the cuticular lipid layer, thus causing dehydration of the insects. 

Monoterpenes are most fi-equently applied as promotors of sorption. The growth of intracellular penetration of a drug in the presence of terpenes is probably connected with an increase of solubility of this drug in the corny stratum of the skin. Monoterpenes can also disturb the regular order of lipids in the intracellular spaces. Monoterpenes as promoters increase the division coefficient of corny stratum/matrix for lipophilic drugs. The penetration speed of lipophilic compounds increases together with their solubility in the promoter (monoterpenes). On the other hand, however, the increase of the penetration speed for hydrophilic compoxmds increases together with the diffusion coefficient [62-68]. 

The mechanisms of the sorption of lipophilic substances to surfaces from an aqueous solution have more to do with displacement from the body of water and solution in a lipid-type surface layer than with the classic sorptive interactions (Fbrstner, 1995). On the basis of their chemical structure and possible surface charges it is possible to distinguish between the following categories of organic environmental chemicals that are relevant to water and soil (Fbrstner, 1995) ... 

Hair is an excellent ion exchange system. Metallic ions may be sorbed to hair in multiple forms such as lipids (e.g., calcium stearate) or as particulates (e.g., metal oxides). Many metallic ions such as copper (-1-2) [11] can adsorb to hair, especially after frequent exposure to swimming pool water. It has been suggested that metallic ions such as chromium, nickel, and cobalt may bind to hair from swimming pool water [11]. Sorption of metallic ions like calcium or magnesium occurs even from low concentrations in the water supply rather than from hair products. However, fatty acids present in hair products enhance the adsorption of most of these metallic ions to the hair surface, as described earlier. Heavy metals such as lead and cadmium have been shown to collect in hair from air pollution [12], and other metals like zinc are available from antidandruff products, from the zinc pyrithione active ingredient. 

Isolation and processing of plant proteins has become an important branch of the food industry. Often, the proteins have to be purified from residual fats and oils, which reduces the shelf time of isolated proteins. HypercrossHnked polystyrene is the material of choice for the removal of all lipids from protein-containing extracts, as well as from isopropyl alcohol where the latter is used for the extraction of lipids from protein masses [50]. Figure 11.5 shows sorption isotherms on Styrosorb 2 for lecithin and oleic acid from pure isopropyl alcohol and its mixtures with water. The equilibrium of lecithin sorption on the microporous Styrosorb 2 from pure isopropyl alcohol is estabhshed within 4h. Addition of water accelerates the sorption process in a water—alcohol mixture of 1 1 (v/v), the equilibrium is estabhshed within 2 h. By reducing the thermodynamic affinity of the medium to both polystyrene and lipids, water also enhances the sorption capacity, so that from the 50% isopropyl alcohol solution as much as 600—700mg/g of lecithin can be taken up by the hypercrosslinked polymer, compared to 400mg/g taken by the XAD-4 resin under the same conditions [51]. Sorption of oleic acid by Styrosorb 2 is smaller than that of lecithin, but, stiU, it reaches 400 mg/g. 

Compounds with high affinity from pesticides with no or lower affinity to the sorbent=chemical filtration or selective elution of analytes Compounds with no or lower affinity from pesticides with higher affinity to the sorbent = separation of matrix components during sorption or washing steps Compounds less volatile than pesticides that undergo thermal cracking while pesticides are carried to a trap by a stream of nitrogen (mainly separation of lipids from thermally stable pesticides)... 

Jimenez A, Fabra MJ, Talens P, Chiralt A (2010) Effect of lipid self-association on the microstructure and physical properties of hydroxypropyl-methylcellulose edible films containing fatty acids. Carbohydr Polym 82 585-593 Jimenez A, Fabra MJ, Talens P, Chiralt A (2013) Phase transitions in starch based films containing fatty acids. Effect on water sorption and mechanical behavior. Food Hydrocolloid 30 408-418 Jin Z, Hsieh F, Huff HE (1994) Extmsion of com meal with soy fiber, salt, and sugar. Cereal Chem 7 227-234... 

Kerler and Schonherr have studied the accumulation of lipophilic chemicals in plant cuticles. Using cuticles isolated enzymatically from mature leaves of Citrus aurantium L., they examined the sorption of a range of C-labeled compounds of widely differing lipid solubilities. They found that logarithms of cuticle/water (Kcm/w) and octanol/water (/(Cow) partition coefficients between 10 and 10, the logarithms were correlated by linear regression equations with coefficients of correlation from 0.980 to 0.988. 

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