Coacervation, complex procedure

Thies, C., Biopolymers and complex coacervation encapsulation procedures. Agro Food Industry Hi Tech, 24(4) (2013) 50-52. 

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 ... 

Interfaciai Tension Procedure. IFT measurements were made by the Wilhelmy plate method. The apparatus was the same as that described previously (2). A standard protocol was followed for all IFT determinations. The desired interface was formed at a specified temperature by partially filling a thermostatted sample holder with the desired aqueous phase. This phase, distilled water (mono triple) or a supernatant aqueous phase isolated from a complex coacervate system, completely covered the Wilhelmy plate (roughened platinum). The desired citrus oil was carefully layered onto the aqueous phase. It had been preheated (or cooled) to the same temperature as the aqueous phase. Once the citrus oil/aqueous phase interface was formed, the Wilhelmy plate was drawn completely through the interface and into the oil phase where it was zeroed. 

Figures 12-14 contain IFT aging curves for several complex coacervate phases against citrus oils. Because these data were obtained by the modified procedure outlined in the Experimental Section, they have been plotted separately from IFT data obtained with the supernatant phases.

Duplicate and triplicate IFT aging curves were obtained at one or two temperatures for most of the interfaces characterized in this study. The replicate IFT data reported in Figures 1,3,4,7,8 and 10-14 show that many IFT aging curves for citrus oil/aqueous phase interfaces differ by a maximum of 1.7mJ/m2. Replicate curves often differ by less than lmJ/m2. Because each IFT aging experiment involved formation and separation of a new complex coacervate and supernatant phase, replicate IFT aging curves measure the combined effect that several factors have on reproducibility. These factors include variability of the complex coacervation procedure, protocol followed for separation of the coacervate and supernatant phases, and the IFT measurement process itself. The variability in solids content of replicate coacervate and supernatant phases shown in Table 1 could contribute to the observed IFT variability. 

Plant cell cultures represent a potentially rich source of secondary metabolites of commercial importance and have been shown to produce them in higher concentrations than the related intact plants. However, plant cell cultures often produce metabolites in lower concentrations than desired and commonly store them intracellularly. These limitations can be overcome by product yield enhancement procedures, including immobilization of cultured cells, and permeabilization, or ideally using a combined immobilization/ permeabilization process with retained plant cell viability. Complex coacervate capsules consisting of chitosan and alginate or carrageenan proved to be effective biomaterials for entrapment, controlled permeabilization of cells and to allow control of capsule membrane diffusivity. 

Coacervation or coprecipitation of host and guest and suspension of the guest molecule in polysaccharide gels, followed by drying, is another common procedure. Microcapsules can be made on the formation of polysaccharide-protein complexes in the presence of a potential host. Preswelled granular starches are potential natural microcapsules (Lii et al., 2001b). 

Complex coacervation is similar to simple coacervation where another complimentary polyelectrolyte is used. Gelatin and gum arabic is a well-estabHshed system for microencapsulation by complex coacervation. Mayya et al. have reported a two-layer encapsulation of paraffin oil, based on a primary layer of interface active polyelectrolyte-surfactant complex, followed by a second layer of the conjugate polyelectrolyte-polyelectrolyte complex [41]. The procedure involves the dispersion of paraffin oil in 1% gelatin solution (pH adjusted to 6.5) containing SDS having concentration less than its CMC, followed by drop-wise addition of the solution of the other polyelectrolyte (1% gum arabic) into the dispersion. The pH is then ad-... 

Essentially the same procedure is reported for encapsulation by gelatin-polyphosphate complex coacervation at pH 4-5 Compared with gum arabic, however, maximum coacervation is achieved at only 1 part of commercially available sodium hexametaphosphates to 10-20 parts of acid-extracted pigskin gelatin. This is due to the lower apparent (ionic) equivalent weight of polyphosphates." The gelatin-... 

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