Gelatin complex coacervates

McMullen, J. N., D. W. Newton, and C. H. Becker, Pectin-gelatin complex coacervates II Effect of microencapsulated sulfamerazine on size, morphology, recovery, and extraction of water-dispersible microglobules. J. Pharm. ScL, 73(12) (1984) 1799-1803. 

Saravanan M., Rao K. R (2010). Pectin-gelatin and alginate-gelatin complex coacervation for controlled drug delivery Influence of anionic polysaccharides and drugs being encapsulated on physicochemical properties of microcapsules. 80, 808-816. 

Table 1 Hsts representative examples of capsule shell materials used to produce commercial microcapsules along with preferred appHcations. The gelatin—gum arabic complex coacervate treated with glutaraldehyde is specified as nonedible for the intended appHcation, ie, carbonless copy paper, but it has been approved for limited consumption as a shell material for the encapsulation of selected food flavors. Shell material costs vary greatly. The cheapest acceptable shell materials capable of providing desired performance are favored, however, defining the optimal shell material for a given appHcation is not an easy task.

Complex Coacervation. This process occurs ia aqueous media and is used primarily to encapsulate water-iminiscible Hquids or water-iasoluble soHds (7). In the complex coacervation of gelatin with gum arabic (Eig. 2), a water-iasoluble core material is dispersed to a desired drop size ia a warm gelatin solution. After gum arabic and water are added to this emulsion, pH of the aqueous phase is typically adjusted to pH 4.0—4.5. This causes a Hquid complex coacervate of gelatin, gum arabic, and water to form. When the coacervate adsorbs on the surface of the core material, a Hquid complex coacervate film surrounds the dispersed core material thereby forming embryo microcapsules. The system is cooled, often below 10°C, ia order to gel the Hquid coacervate sheU. Glutaraldehyde is added and allowed to chemically cross-link the capsule sheU. After treatment with glutaraldehyde, the capsules are either coated onto a substrate or dried to a free-flow powder. 

Eig. 2. Elow diagram of a typical encapsulation process based on the complex coacervation of gelatin with gum arabic. 

Xing, F., Cheng, G., Yang, B., Ma, F. (2004). Microencapsulation of capsaicin by the complex coacervation of gelatin, acacia and tannins. Journal of Applied Polymer Science, 91,2669-2675. 

The encapsulation of various essential oils has intrigued the food, cosmetic, and pharmaceutical industries for some time. Several encapsulation systems based on the complex coacervation of gelatin have been used to encapsulate a range of essential oils. However, variable results have been obtained, especially with citrus oils. 

In order to characterize the behavior of such oils, their interfacial behavior against water and the aqueous phases that exist in several gelatin-based complex coacervation systems has been studied. This report summarizes the interfacial tension (IFT) data obtained and is an extension of a preliminary study (1). 

Complex Coacervation Procedures. Gelatin/alginate (G/A), gelatin/ polyphosphate (G/P), and gelatin/gum arabic (G/GA) complex coacervate and supernatant phases were used in this study. G/A complex coacervate and supernatant phases were formed at pH 4.2 with a 3.7 1 (w/w) mixture of gelatin (227 bloom) and sodium alginate (total solids 1.8 wt. percent). G/P complex coacervate and supernatant phases were formed at pH 4.4 with a 9 1 (w/w) mixture of gelatin (283 bloom) and polyphosphate (total solids ... 

Citrus oils contain a number of components and are complex liquids. The same is true for the aqueous phases formed by complex coacervation of gelatin. Accordingly, the IFT behavior of citrus oils against water and the aqueous phases produced by compex coacervation reflects the interfacial behavior of complex systems. Changes in IFT can be caused by a number of possible chemical and/or physical changes. For example, several chemical reactions could occur. 

Citrus oils readily form oxygenated products that are likely to congregate at oil/water interfaces and thereby cause a detectable change in IFT. The aldehydic components of citrus oil could react with the amine groups of the gelatin molecules present in the aqueous phases formed by complex coacervation and thereby affect IFT. In addition to chemical reactions, physical changes can occur at an interface and alter IFT. A visible interfacial film can form simply due to interfacial interactions that alter the interfacial solubility of one or more components. No chemical reactions need occur. An example is the formation of a visible interfacial film when 5 wt. per cent aqueous gum arabic solutions are placed in contact with benzene (3). Interfacial films or precipitates can also form when chemical reactions occur and yield products that congregate at interfaces. 

Pahnieri, G.F. Lauri, D. Martelli, S. Wehrle, P. Methoxy-butropate microencapsulation by gelatin-acacia complex coacervation. Drug Dev. Ind. Pharm. 1999, 25 (4), 399-407. 

Carboxymethylcellulose sodium forms complex coacervates with gelatin and pectin. It also forms a complex with collagen and is capable of precipitating certain positively charged proteins. 

Gelatin-acacia complex coacervation has been used in the preparation of microcapsules of vitamin Pindolol-loaded alginate-gelatin beads have been developed for the sustained release of pindolol. ... 

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