Ossein, acid processing

In the alkali process, demineralized bones (ossein) or cattle skins are usually used. The animal tissue is held in a calcium hydroxide (lime) slurry for a period of 1-3 months at 15-20°C. At the end of the liming, the stock is washed with cold water to remove as much of the lime as possible. The stock solution is then neutralized with acid (HGl, H2SO4, H3PO4) and the gelatin is extracted with water in an identical manner to that in the acid process. 

In the acid process, the bones and skins are treated in a vessel containing a dilute solution of acid for a predetermined period of time. Then, the acid is washed out with cold water. In the alkali process, the demineralized bones (demineralization is mostly done with acid solutions to remove calcium and other salts from the bone to prepare the collagen-rich bone material known as ossein) are placed in liming pits and soaked in a lime suspension for longer than 60 days. For the hides or skins, a caustic soda solution is used for a shorter period of time. After this treatment, the raw material is washed thoroughly to remove any residual lime. The acid pretreatment is mostly used for skin, while the alkali pretreatment is mostly used for bones (Petersen and Yates, 1977). 

The osseine, or defatted pigskins, is first treated with acids or alkali in order to remove undesirable components. The acid process leads to A-gelatine, which is mostly used in the food industry. Alkali yields the B-gelatine used in photographic film. 

Croda 50 Bloom Gelatin] Croda 60 Bloom Alkaline Processed Gelatin] Croda 160 Bloom Limed Gelatin] Croda 190 Bloom Acid Ossein... 

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