Of gelatin

Dissolve 6 g. of gelatin in about 250 ml. of warm water. Carry out the formaldehyde titration on 25 ml. of the solution note in this case that the solu> tion is acid to phenolphthalein. 

Uses of gelatin are based on its combination of properties reversible gel-to-sol transition of aqueous solution viscosity of warm aqueous solutions abUity to act as a protective coUoid water permeabUity and insolubUity in cold water, but complete solubUity in hot water. It is also nutritious. These properties are utilized in the food, pharmaceutical, and photographic industries. In addition, gelatin forms strong, uniform, clear, moderately flexible coatings which readily sweU and absorb water and are ideal for the manufacture of photographic films and pharmaceutical capsules. 

Other Food. Tartaric acid is also used ia the manufacture of gelatin (qv) desserts and ia fmit jellies, especially ia pectin jellies for candies where a low pH is necessary for proper setting. It is used as a starch modifier ia starch jelly candies so that the product flows freely while being cast. It is used ia hard candy because its melting poiat permits it to fuse iato the "glass" and does not contribute to moisture. 

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. 

The original Polacolot negative had water-coated intedayers of gelatin (60). The SX-70 and Polacolot 2 negatives use as intedayers a combination of a polymeric latex with a water-soluble polymer. A key development was the constmction of lattices that function as temporary batnets, reducing interimage problems. The water-soluble polymer functions as a permeator, so that the harder properties ate tunable (61). 

Bone cleaning is the second stage of en2ymatic extraction. The soHd bone fraction from the first separation is mixed 1 1 with hot water (65—75°C) and treated with alkaline-type proteases. After a reaction time of one hour, the bones are separated and washed with water. The cleaned bones make an excellent raw material for the production of gelatin. 

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