Encapsulation matrix ingredient

Viscosity. Viscosity and solubility may be the two most important characteristics of an encapsulation matrix ingredient. The increase in solids to the dryer at a constant solids/flavor ratio can greatly increase the economic efficiency of an operation. Most processing systems have a maximum viscosity at which they can operate. Proper atomization may also affect the flavor retention (Reineccius and Bangs 1985). The low viscosity of maltodextrins and corn syrup solids is shown in Figure 2. The viscosity of these products... 

Low Cost-Reliable Supply. Maltodextrins and corn syrup solids carry a much lower cost than almost all other encapsulating matrix ingredients, They are produced both in the U.S. and in foreign countries by several suppliers, so they are readily available. When used alone or as one of a combination of encapsulation matrix ingredients, maltodextrins and corn syrup solids are an effective part of the encapsulating system. 

Controlled release. For practical use the active ingredient must be released. A drug must be delivered with well defined kinetics. Sometimes it is not the encapsulated ingredient that is released but a by-product. This is the case when the encapsulated product is an enzyme or a catalyst. Encapsulation may have the objective to limit release, but in some cases to make it more rapidly available. A typical example is an instant powder consisting of aggregates made of fine particles that are insoluble, in a very soluble matrix. 

For incorporation of the active ingredient inside a liquid matrix (as a solution, emulsion, or suspension), the first step of encapsulation is the dispersion of this liquid as droplets, which can be classified into four categories. 

Spray drying is the most commonly used method in the food industry. Bioactive ingredients microencapsulated by this method include fats and oils, flavours, essential oils and other oil-soluble bioactives. Water-soluble bioactives can also be encapsulated by spray drying, where the encapsulant forms a matrix structure rather than a film surrounding the core. This process typically involves the dispersion of the core material into a solution of the encapsulant (e.g., protein, carbohydrate) and atomization of the mixture into the drying chamber. This leads to evaporation of the solvent... 

In general, spray dried flavourings can be considered small capsules of an active volatile and/or tasting ingredient which is embedded in a matrix material. The spray dried capsules are almost spherical particles, each containing a high number of oil-globules or solid particles. Most liquid or solid materials can be encapsulated, whether they are hydrophobic or hydrophilic. 

Nanostructured biopolymers and emulsions lend themselves to encapsulation of food ingredients that need to be protected from their environment until they are released at a specific time or site. Controlled breakdown of the matrix material and release of the encapsulated core... 

As in any other system, the phase state of the structural elements of nanoparticle dispersions may change induced by variation of physical parameters. This aspect becomes most interesting if the matrix material is affected, e.g., the bulk stmcture of a nanosphere or the wall material of a nanocapsule membrane. This case has very promising practical applications a nanocapsule or a nanoparticle may be loaded while being in one phase state and subsequently sealed by a phase transition. This possibly allows one to produce prefabricated particle dispersions where the hnal encapsulation step is accomplished by addition of the active ingredient at any given point in time. 

As for other supercritical processes, it is possible to micronize one substrate or more—for instance, to encapsulate an active substance in a biocompatible polymer. In such a case, the purpose is to obtain a controlled-release system of the active substance, and both materials (the active ingredient and the polymer) must be dissolved in the CO2 mixture. Depending on the relative solubility of the two materials in the supercritical medium, one can obtain an encapsulated product or a composite matrix of the two products (26-28). 

Matrix encapsulation is the simplest structure, in which the active ingredient (core) is much more dispersed within the carrier/shell material either in the form of relatively small droplets or more homogenously distributed/embedded in a continuous matrix of wall material. The active ingredients in the matrix type morphology are also present at the surface unless there is additional coating applied. 

The release mechanism of carbohydrate-based matrix capsules prepared by spray drying is solvent activated, which means that the powder readily dissolves upon contact with water. This release mechanism has limited the range of appUcations to dry products in the past. However, through selection of the matrix constiments and buildup of more sophisticated physical structures, a controlled release of encapsulated ingredients can be achieved. This is of particular importance with respect to the release of pharmaceutical or food ingredients, which need to be delivered to specific parts of the gastrointestinal systan. " " ... 

The characterization of the particles in terms of size and shape is essential and has a direct impact on the behavior of this particulate system. These data may be correlated with encapsulation efficiency, the form of release of the active ingredient from the matrix, and the efficiency in protecting the bioactive. 

In general, compared to irregular xerogel matrix particles, microparticles encapsulate a far higher load of active ingredient (up to 90% in weight of the final materials), and afford a wide control over the release rate (from hours to months and up to unlimited retention of the entrapped ingredient), thanks to control of the microstructure and thus by the initial sol-gel chemistry. 

The bioactive substance that is encapsulated is called the core material, active ingredient or agent, or internal phase. The material encapsulating the core is referred to be a matrix, as support material, coating, shell, or wall material. 

Diffusion is another important mechanism in release into foods because it is dominant in controlled release from matrix systems (microspheres). Diffusion occurs when the active ingredient passes through the encapsulating material. This mechanism can occur on a macroscopic scale (as through pores in the matrix) or on a molecular level, by permeation through the structuring material. Examples of diffusion-release systems are shown in Figure 32.4. 

Delivery systems can be solid or liquid, depending on the food matrix where they are introduced. Some examples of solid systems are spray-dried and gel microparticles, whereas liquid systems include liposomal and emulsified systems. Each of these delivery systems has its own specific advantages and disadvantages for encapsulation, protection, and delivery of food ingredients. These aspects are briefly discussed in the following, together with a description of the basic principles of each technique, its physicochemical characteristics, and the current challenges for its application in foods. 

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