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Amphiphilic biopolymers

Another characteristic property of many biopolymers (proteins, modified starch, chitosan, etc.) which is useful for the encapsulation of bioactive molecules is their ability to adsorb at the oil-water interface and to form adsorbed layers that are capable of stabilizing oil-in-water (OAV) emulsions against coalescence (see Table 2.2). It is worthwhile to note here that the formation of an emulsion is one of the key steps in the encapsulation of hydrophobic nutraceuticals by the most common technique used nowadays in the food industry (spray-drying). The adsorption of amphiphilic biopolymers at the oil-water interface involves the attachment of their hydrophobic groups to the surface of the oil phase (or even their slight penetration into it), whilst their hydrophilic parts protrude into the aqueous phase providing a bulky interfacial layer. [Pg.61]

Another method applicable to interfaces is the determination of the partial moleeular area a of a biopolymer partitioning into a lipid monolayer at the water-air interfaee using the Langmuir trough [28]. The first step is to record a series of pressure Ti-area (A) isotherms with different amounts of an amphiphilic biopolymer spread at the interface. [Pg.2819]

The adsorption isotherms of fenugreek gum are much more explicit and more characteristic of amphiphilic biopolymers than those of the other gums... [Pg.367]

Proteins are biopolymers of some 22 different amino acids. Because of the variation in physical-chemical properties, mainly polarity and electrical charge, between the constituent amino acids, protein molecules are am-pholytic (i.e., containing positively and negatively charged groups) and more or less amphiphilic (i.e. comprising polar and apolar domains). These properties, in turn, lead to the formation of complex three-dimensional (3D) structures. [Pg.100]

C. Prata, F. Giusti, Y. Gohon, B. Pucci, J.-L. Popot, C. Tribet (2001) Non-ionic amphiphilic polymers derived from Tris(hydroxymethyl)-acrylamidomethane keep membrane proteins soluble and native in the absence of detergent. Biopolymers, 56 77-84... [Pg.159]

It is found that, even a monolayer of lipid (on water), when compressed can undergo various states. In the following text, the various states of monomolecular films will be described as measured from the surface pressure, n, versus area, A, isotherms, in the case of simple amphiphile molecules. On the other hand, the Il-A isotherms of biopolymers will be described separately since these have a different nature. [Pg.72]

Let us consider the various possible types of biopolymer-surfactant interactions. We first note that, because of the amphiphilic nature of both biopolymers and surfactants, it can be envisaged that the mechanistic interpretation could be based on attractive or repulsive interactions acting between the original biopolymer and surfactant molecules/particles or between biopolymer particles modified by the surfactants. For example, attractive interactions could arise from ... [Pg.176]

In addition to the necessary protection of the contents of the emulsion droplets, effective encapsulation technology requires that the release of the active matter be controlled at a specified rate. Benichou et aL (2004) have demonstrated that a mixture of whey protein isolate (WPI) and xanthan gum can be successfully used for the controlled release of vitamin Bi entrapped within the inner aqueous phase of a multiple emulsion. The release profile, as a function of the pH of the external aqueous phase, is plotted in Figure 7.25. We can observe that the external interface appears more effectively sealed against release of the entrapped vitamin at pH = 2 than at pH = 4 or 7. It was reported that an increase in the protein-to-potysaccharide ratio reduced the release rate at pH = 3.5 (Benichou et aL, 2004). More broadly, the authors suggest that compatible blends of biopolymers (hydrocolloids and proteins) should be considered excellent amphiphilic candidates to serve as release controllers and stability7 enhancers in future formulations of double emulsions. So perhaps mixed compatible biopolymers wall at last allow researchers to... [Pg.286]

A large number of macromolecules possess a pronounced amphiphilicity in every repeat unit. Typical examples are synthetic polymers like poly(l-vinylimidazole), poly(JV-isopropylacrylamide), poly(2-ethyl acrylic acid), poly(styrene sulfonate), poly(4-vinylpyridine), methylcellulose, etc. Some of them are shown in Fig. 23. In each repeat unit of such polymers there are hydrophilic (polar) and hydrophobic (nonpolar) atomic groups, which have different affinity to water or other polar solvents. Also, many of the important biopolymers (proteins, polysaccharides, phospholipids) are typical amphiphiles. Moreover, among the synthetic polymers, polyamphiphiles are very close to biological macromolecules in nature and behavior. In principle, they may provide useful analogs of proteins and are important for modeling some fundamental properties and sophisticated functions of biopolymers such as protein folding and enzymatic activity. [Pg.48]

Stabilization of the interfaces between oil and water is of great importance in emulsion technology. Interfaces are usually stabilized with the help of amphiphihc molecules such as low molecular weight surfactants and biopolymers. Interfaces are two-dimensional nanoscopic spaces where amphiphilic molecules accumulate and self-assemble. Time-scales are very important in emulsion technology, as the adsorption events at the newly created interface take place in the millisecond range and are governed by the diffusion properties of the surfactant molecules (Brosel and... [Pg.209]

Experimental methods based on an analysis of interactions of biological macromolecules with free or immobilized nonpolar or amphiphilic ligands are most commonly used at present to study the relative hydrophobicity of biopolymers. [Pg.189]

Lu Y, Liu L et al (2007) Novel amphiphilic ternary polysaccharide derivates chitosan-g-PCL-b-MPEG synthesis, characterization, and aggregation in aqueous solution. Biopolymers 86 403 08... [Pg.43]

Compatible blends of biopolymers (hydrocolloids and proteins) are excellent future amphiphilic candidates that under certain combinations will serve both as release controllers and stability enhancers for the future preparations of double emulsions. [Pg.403]

The investigations of thermotropic PLCs commenced almost two decades after studies of mesophases employing rodlike polymers(21) and virus particles(22) in solution were initiated. Like their MLC analogues (aqueous solutions of amphiphilic molecules) the polymeric lyotropic liquid crystals which form in solutions of rigid, rodlike polymers (helical biopolymers, and more recently, semiflexible aromatic amides) constitute a distinct class of liquid crystals. Unlike the MLC analogues, however, the lyotropic PLCs are not necessarily stabilized by specific interactions between the polymer chain... [Pg.69]

Besides entanglements, a second kind of crosslinking process leading to gelation involves physical associations such as polar-polar interactions, ionic forces, colloid interactions, hydrogen bonding, or complex associations such as formation of multiple helices and/or coUed-coils in biopolymers, self-assembly with formation of micellar aggregates in amphiphilic block copolymers, and so on. [Pg.164]


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See also in sourсe #XX -- [ Pg.59 ]




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