Water-gelatin system

Drop deformability in water-gelatine systems with either PVAI or dextran... 

The photochemistry of four triphenylmethane acid dyes was studied in poly(vinyl alcohol), methylcellulose and gelatin films. These model systems were chosen with a view to elucidating the complex free-radical reactions taking place in the heterogeneous dyed wool/ water/air system on exposure to UV radiation. The dye fading mechanism seems to involve an excited triplet state of the dye molecule [ 164] The rate of fading is governed by ... 

Figure 7.1 Phase diagram of the water + gelatin + locust bean gum (LBG) system at pH = 5.0, ionic strength = 0.002 M and T= 40 °C (—) binodal ...

Nowadays it is established that confocal microscopy observation can be a more sensitive method to assess die phase state of mixed biopolymer systems than the traditional centrifugation or viscometric methods (Alves et al., 1999, 2001 Vega et al., 2005). Indeed, microscopy can demonstrate that a system may be already phase-separated at compositions well below the apparent binodal line (as determined by these other methods). The report of Alves et al. (2001) demonstrates the relationship between specific compositional points in the phase diagram (Figure 7.1) and the observed microstructure (Figures 7.2 and 7.3) for water + gelatin + locust bean gum (LBG). The white areas in Figures 7.2 and 7.3 corre-... 

Figure 7.2 Evolution of the microstructure in the water + gelatin + LBG system (Figure 7.1) for compositions of 0.8 % LBG and increasing gelatin concentration, at pH = 5.0, ionic strength = 0.002 M and 7 = 40 °C, Path 1 (a) point A3 (b) point A5 (c) point A6. Each scale bar represents 50 pm. Reproduced from Alves et al. (2001) with permission.

Alves, M.M., Antonov, Yu.A., Goii9alves, M.P. (2000). Phase equilibria and mechanical properties of gel-like water-gelatin-locust bean gum systems. International Journal of Biological Macromolecules, 27, 41 17. 

When native starch grains are heated in an excess of water, gelatinization occurs, which implies that amylose leaches from the granules and that the latter greatly swell and eventually fall apart. If the system then is cooled and the amylose concentration is above the chain overlap concentration c, corresponding to 2-4% starch (depending on starch type), a gel is formed. This is mainly due to the formation of microcrystallites of... 

Figure 7.12. Effect of the shear rate (top), the initial drop diameter (middle), and the viscosity ratio (bottom) on the drop aspect ratio for the systems water-gelatin-dextran (W-G-D, circles) and water-gelatin-polyvinyl alcohol (W-G-P, squares) [Talstoguzov et al., 1974].

The organic melt is emulsified in water with the aid of a suitable nonionic agent and stabilized by a protective colloid, e.g. potato starch gelatinized with water. The system is crystallized by cooling, and the crystals are separated from the emulsion and washed with water. The operation may be repeated if required. A typical example is shown in Figure 8.57 where five or six emulsion-crystallization cycles yield an almost pure naphthalene at an overall yield of 70 per cent compared with a less pure product at a 2 per cent yield by seven conventional fractional crystallization steps. The high efficiency of the emulsion crystallization is apparently due to the fact that crystal agglomeration does... 

Tan I., Wee C.C., Sopade P.A., Halley P.J., Investigation of the starch gelatinization phenomena in water-glycerol system Application of modulate temperature differential scanning calorimetry, Carbohyd. Polym., 58, 2004,191-204. 

Gelatin is a mixture of purified protein fractions obtained by partial add hydrolysis (Type A gelatin) or alkali hydrolysis (Type B gelatin) of animal collagens. It is insoluble in cold water and in alcohol, but is soluble in hot water. In hot water, gelatin forms a gel on cooling to 35-40°C. At temperatures >40°C, the system exists as a solution. Therefore, the gelatin solutions must be used when warm to avoid gel formation. 

Gelatin, a poly(peptide), finds extensive use in the preparation of microcapsules for use in drug delivery and the encapsulation of various water-insoluble oils used in cosmetics. These gelatin systems are normally crosslinked to overcome the water solubility of the polymer. 

The intensity size distribution functions in water-BSA-gelatin and water-BSA -gelatin systems at different q values are shown correspondingly in Figs. 3 and 4. 

An addition of NaCl in the ternary water-gelatin-BSA" system results in the partial dissociation of the complex aggregated, and the absence of free BSA molecules (Fig. 5). On the other hand, an addition of NaCl in the in the initial binary solutions of BSA and gelatin (0.25 M NaCl) leads to the partial dissociation of the complex aggregated, and the absence of free BSA molecules (Fig. 6). 

FIGURE 6 The effect ofan addition of NaCI in the binary water-gelatin and water-BSA system on the intensity-size distribution functions of the ternary water-gelatin (0.25 wt%)-BSA (0.25 wt%) system, obtained by mixing of the binary salt solutions of gelatin and BSA . 

Fum ric Acid. Eumaric acid [110-17-8] C H O, is unique in its low solubiUty in cold water and slow rate of solution, making it ideal for use in chilled biscuit leavening systems and for dry pudding mixes and beverage powders. It is also used for gelatin desserts, pie filling, fmit juices, and wine. Eumaric acid is produced by the acid-catalyzed isomerization of maleic acid (8,9) (see Maleic anhydride, maleic acid, and fumaric acid). 

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. 

---