Carrier matrix

To date most of the work which has been done with supercritical fluid extraction has concentrated on the extraction of analytes from solid matrices or liquids supported on an inert solid carrier matrix. The extraction of aqueous matrices presents particular problems [276-278]. The co-extraction of water causes problems with restrictor plugging, column deterioration, and phase separation if a nonpolar solvent is used for sample collection. Also, carbon dioxide isay have limited extraction efficiency for many water soluble compounds. 

In contrast to the extensive exploitation of the trapped aqueous volume of the liposomes that serves as nanocontainer for water-soluble molecules, the phospholipid bilayer has not been given the same attention for its use as carrier matrix for lipophilic drugs. An exploratory survey of the number of cited literature references in Medline performed in February 2005 gave the following result. With the general keywords drug and... 

The typical flavour load of a spray-dried product amounts to 18-25%. Besides the drying process, the flavour components are also encapsulated in the carrier matrix. After the slurry has been atomised , all volatile components, including water, which are located at the surface of the droplet are immediately evaporated. Thereby the remaining carrier substance forms a membrane around the droplet. This membrane is semipermeable and inhibits further evaporation of flavour molecules. This production step is controlled by diffusion mechanisms. Water as a molecule with a small molecular size can pass through the membrane, while the larger flavour molecules are not able to permeate it. 

There may be competing factors between emulsion size and extractable surface oil that produce these results. While the finer emulsions have less extractable surface oil which should improve shelf-stability, the total surface area of the oil droplets in these powders is greater (Table V). The lower amount of surface oil provides less oil that is openly exposed to oxidation but the greater surface area of the droplets in the carrier matrix provides greater possibility for oxidation once oxygen has permeated the spray dried particles. 

Unfortunately, bacitracin causes nephrotoxicity [36] and so its use as a suitable adjuvant to overcome the enzymatic barrier is quite questionable. Interestingly, it was demonstrated recently that bacitracin, when covalently linked to a mucoadhesive polymer, still displays its inhibitory activity [30]. The immobilization to an unabsorbable drug carrier matrix is believed to lead to an exclusion of systemic toxic side effects, but detailed toxicological studies are necessary to prove this hypothesis. 

In heterogeneous inorganic biomimics objectives (2)—(4) are resolved more easily than for organic mimics. Many acidic and basic sites on an inorganic carrier (matrix) form a situation in the biomimetic system when a definite quantity of these sites will display the required geometry for substrate-activated complex formation. 

Sensory properties are also influenced by particle size. Each crystalline material in a food has a critical threshold detection size, where above that critical size the particles are detected in the mouth and the food has a coarse texture. The critical threshold detection size depends on the properties of the crystals, namely, how rapidly they melt or dissolve in the mouth. Crystals that melt rapidly in a viscous carrier matrix, such as ice crystals in a frozen dessert, can be up to 50 im in size before sensory detection. In contrast, crystals that are hard and dissolve slowly in the mouth, like lactose crystals in sandy ice cream, can be no larger than about 15 gm before they are detected. A fine chocolate will have the majority of particles smaUa-than 20 gm to avoid sensory coarseness. 

Martynenko, N.N., Gracheva, I.M., Saiishvili, N.G., Zubov, A.L., ETRegistan, G.I., and Lozinsky, V.I. (2004). Immobilization of Champagne yeasts by inclusion into cryogels of polyvinil alcohol Means of preventing cell release from the carrier matrix. Appl. Biochem. Microbiol, 40, 158-164. 

Burow and Minoura performed a similar kind of investigation to prepare protein imprinted polymers [48]. They used methacrylate modified silica particles as the carrier matrix on which imprinted sites were created. Using acrylic acid as the functional monomer and A,TV -1,2-diethylene bisacrylamide as the cross-linker, template polymerisation was carried out in the presence of glucose oxidase. This approach led to formation of a thin layer of cross-linked polymer film on the silica surface. After removing the template protein, substrate selectivity of the polymer was tested. Preferential affinity of the polymer for its template suggests the formation of substrate-selective binding sites in the polymer matrix. 

The coefficient of extinction r mentioned here is approximately comparable but not identical with the coefficient of extinction in Beer-Lambert s law. r is dependent on an interaction between the absorbing molecules and the reagent carrier matrix. 

In the majority, herbal teas require a carrier matrix. Maltodextrines of various qualities are used. These carbohydrates are capable of retaining volatile compounds to a certain extent, as will be discussed in 2.1.5.3.3. These results can also be transferred to other extracts. 

The preservation effect for flavours, however, proceeds oppositely. Kopelman, Mey-dav and Wilmersdorf [45] have demonstrated with freeze-dried citrus flavourings that the flavour preservation increases with rising DE-value. For practical applications, analysis of the raw material and pre-trials with various carrier matrixes have, therefore, to be employed to find the optimum. The groups of Thijssen as well as Flink and Karel [45-56] hme performed exhaustive basic studies on this problem. 

Support (carrier, matrix) - the solid matter, the participant of chemical modification. Support might be both mono or polycrystalline, amorphous, more or less dispersed and pelicular. There are inherent (structural) functional groups on the surface of support. The latter are responsible for the reactivity of surface. Normally, inorganic oxides or metals covered with oxide films are used as supports. Not less than 90% of studies in this field is performed on a silica surface. This comes from the following facts. Firstly, silica has soft surface hydroxyls secondly, silica is commercially available in a wide range of pore, particle sizes and specific surface areas. 

Hydrophilicity/hydrophobicity of the carrier matrix, which influences type and strength of non-covalent protein-matrix interaction. In addition, it can influence the adsorption, distribution and availability of the substrate and product. 

If one could conclusively show that there is an effect of plasticizers on reaction rate that is independent of moisture content or a , then this would demonstrate the significance of matrix properties for governing reaction rate. Labuza et al. (1977) studied the Maillard reaction and measured the effects of several parameters. These included temperature, reactant concentration, pH, buffers, and the addition of humectants. The formulation consisted of glucose and casein as reactants within a carrier matrix of microcrystalline cellulose and an inert lipid. Reaction rate was measured both as glucose loss, lysine loss, and pigment production (A42o). 

Many food processes, which affect food quality and stability, are diffusion controlled (Karel et al., 1994 Roos, 1995). Transport of key penetrants such as water into or out of a polymeric food matrix can play a critical role in food quality and stability. Water is one of the major components and a very good plasticizer in foods. The quality and stability of dehydrated products, multi-domain foods, and the performance of biofilms and encapsulation and controlled release technologies are affected by moisture transport. The rates of molecular mobility and diffusion-limited reactions strongly depend on the factors surrounding the food. Temperature and water activity (fl ) pl y significant roles in penetrant diffusion. The physical state of the carrier matrix, chemistry, size, and structure of diffusing molecule and specific... 

Microencapsulation of flavors is a technology of enclosing flavor compounds (core materials) in a carrier matrix. An amorphous or metastable solid is normally used as a carrier matrix. Microencapsulation is useful for improving the chemical stability of flavor compounds, providing controlled release of flavor compounds from microencapsulated flavor products, providing a free-flowing powder with improved handling properties and physical protection of volatile properties of flavor. 

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