Spray-dried microcapsules

Characterization and singlet oxygen quenching ability of spray-dried microcapsules of edible biopolymers containing antioxidant molecules. Journal of Agricultural and Food Chemistry, Vol. 58, No.l3, (June 2010), pp. 8004-8011, ISSN 0021-8561. 

Perez-Alonso, C., Baez-Gonzalez, J.G., Beristain, C.L, Vernon-Carter, E.J., Vizcarra-Mendoza, M.G., 2003. Estimation of the activation energy of carbohydrate polymers blends as selection criteria for their use as wall material for spray-dried microcapsules. Carbohydr. Polym. 53(2), 197-203. 

FIGURE 61.1 Schematic representation of a microcapsule containing pigment substance and SEM image of spray-dried microcapsules loaded with dye. 

A second possibility to increase the functionality of spray-dried emulsions is to build up a specific structure with desired functionality at the oil-water interface. Enzymatic cross-linking of proteins at the oil-water interface can increase the stability of emulsions. Cross-linking of a-lactalbumin at the interface of an emulsion increased the physical stability [28]. Kellerby et al. [29] investigated the influence of network formation through transglutaminase on the oxidation stability of caseinate-based fish oil emulsions. The authors showed that cross-linking increases the cohesiveness of the proteins at the interface but not lipid oxidation in liquid emulsions. Data from our own research showed that also in spray-dried microcapsules transglutaminase cross-linked proteins do not act as additional barrier (data not published). 

Finally, protein-based fibrils can be formed and may be used to increase the stability of the interfacial film in spray-dried microcapsules. In concentrated protein solutions depending on the environmental conditions (pH, ionic strength, temperature) and the process conditions (e.g. shear), fibril structures or spherical aggregates may occur as a result of hydrolysis and denaturation [41,42]. In literature the formation of fibrils using p-lactoglobulin and whey protein isolate is described. These amyloid-like anisotropic aggregates are formed at pH values below the isoelectric point (pH 2.0. 0) and several hours of heating (at or above 80 °C)... 

Controlled Fibril Formation for the Stabilisation of the Oil-Water Interface and Enhancement of the Functionality of Spray-Dried Microcapsules... 

Scanning electron microscopy of spray dried microcapsules was performed by JSM-6460, JEOL, Japan. 

SEM image of powder of microcapsules obtained from 0.35% SDS emulsion is shown in Figure 25. The image exemplifies typical visual appearance of spray dried microcapsules. No difference in visual appearance of microcapsules obtained from emulsions having different concentration of SDS was observed by scanning electron microscopy. 

Encapsulation efficiency was tested by extraction of oil from spray drayed microcapsules. Figure 26 shows influence of SDS concentration in emulsion on the relative mass of extracted oil from spray dried microcapsules. 

Influence of encapsulated oil type on properties of spray dried microcapsules... 

Spray Drying. Spray-dry encapsulation processes (Fig. 7) consist of spraying an intimate mixture of core and shell material into a heated chamber where rapid desolvation occurs to thereby produce microcapsules (24,25). The first step in such processes is to form a concentrated solution of the carrier or shell material in the solvent from which spray drying is to be done. Any water- or solvent-soluble film-forming shell material can, in principle, be used. Water-soluble polymers such as gum arable, modified starch, and hydrolyzed gelatin are used most often. Solutions of these shell materials at 50 wt % soHds have sufficiently low viscosities that they stiU can be atomized without difficulty. It is not unusual to blend gum arable and modified starch with maltodextrins, sucrose, or sorbitol. 

In addition, Montenegro et al., (2007) determined that the photosensitized RF-mediated degradation of vitamins A, D3, and RF itself in skimmed milk was strongly reduced by the addition of small amounts of lycopene-gum arabic-sucrose microcapsules, prepared by spray-drying. Under these conditions, the bulk properties of the skimmed milk were unmodified. The main photoprotection mechanism of the milk vitamins was the efficient quenching of the 3Rf by the protein moiety of GA. Small contributions (<5%) to the total photoprotection percentage was due to both inner filter effect and 1O2 quenching by the microencapsulated lycopene. 

Thus, spray-dried xylan/ESlOO microparticles were produced at different polymer weight ratios dissolved in alkaline and neutral solutions, separately. More precisely, xylan and ESIOO were dissolved in 1 1 and 1 3 weight ratios in 0.6 N NaOH and phosphate buffer (pH 7.4). Then, the suspensions were spray-diied at the feed rate of 1.2 mL/min (inlet temperature of 120°C) using a Biichi Model 191 laboratory spray-dryer with a 0.7 mm nozzle, separately. Cross-linked xylan microcapsules were also coated by ESIOO after spraydrying at the same conditions. 

Because most food matrices are water soluble, many efforts were directed to the formulation of lipophilic pigments (mainly carotenoids) into water-soluble formulations (powders or gels). For hydrophilic pigments like flavonoids, polar dried microcapsules are the most popular ways to stabilize their functionality. Extracts rich in P-carotene were encapsulated using three different encapsulation techniques (spray drying, drum drying, and freeze drying)." ... 

Kagami, Y., Sugimura, S., Fujishima, N., Matsuda, K., Kometani, T., Matsumura, Y. (2003). Oxidative stability, structure, and physical characteristics of microcapsules formed by spray drying of fish oil with protein and dextrin wall materials. Journal of Food Science, 68, 2248-2255. 

Spray drying. Microencapsulation by spray drying is an ideal method for poorly water-soluble drugs. The drug is dispersed in polymer (coating) solution, and then this dispersion is atomized into an airstream. The air, usually heated, supplies the latent heat of vaporization required to remove the solvent and forms the microencapsulated product. This technique is employed most commonly when microcapsules are intended for oral use because the resulting microspheres are porous in nature, and large batch sizes are required.89... 

These three steps may be repeated to reach the final structure. For example, microcapsules obtained by spray drying of polymer/active solution may be coated by a melted solution. The first encapsulation insures immobilization and stabilization of the active ingredient, while coating allows control of the level of protection and release. 

Probiotics may be encapsulated in protein-based emulsions. Picot and Lacroix (2003) prepared microcapsules by emulsifying milkfat containing micronized skim milk powder (as a surrogate for freeze-dried bacteria) with heat denatured whey proteins and then spray drying. Incorporation rates of up to 58% milk fat and 29% skim milk... 

Pieot, A., and Laeroix, C. (2003). Production of multiphase water-insoluble microcapsules for eell eneapsulation using an emulsification/spray-drying teehnology. J. FoodSci. 68,2693-2700. 

Rapidly dispersing granules of microcapsules were produced using water-soluble polymers in the suspension prior to spray drying [22]. Polyvinyl alcohol was a preferred polymer. 

Takenaka H, Kawashima Y, Lin SY. Preparation of enteric-coated microcapsules for tableting by spray-drying technique and in vitro simulation of drug release from the tablet in GI tract. ] Pharm Sci 1980 69 1388-1392. 

Various physical methods of preparing microcapsules such as spray drying and pan coating are available. 

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