Volume 13: Industry Processes and Controls
8. Other industries
Gelatine
Processes involved

8.58 Gelatine is used in a huge number of products, including cosmetics, pharmaceuticals, glue, bone china, photographic chemicals and human food.

8.59 Approximately 60 per cent of gelatine is used in food preparation, 20 per cent in pharmaceutical manufacture, 15 per cent in photographic use and the remainder for other non-food use. ¹ Most gelatine used in food is produced by the 'acid' process (see below), which utilises soft bones and hides. ²

Processes involved

8.60 Gelatine is made from the hides and bones of animals, including cattle. Different raw materials receive different initial treatment. ³

• Pigskins are brought directly from the abattoir and kept in cold storage until processing. ⁴
• Calf and cattle hides are cleansed at the tannery and treated with alkali to separate the undersurface (or 'flesh split') from the surface of the hide. The flesh split is almost pure collagen, and is ideally suited to the manufacture of gelatine. The split is preserved with salt or caustic lime and kept until processing. ⁵
• Fresh, chilled bones are brought directly from the abattoir and processed immediately - they are ground down, washed, degreased with water, dried, classified according to grain size and put into store. Over a period of several days, the resulting bone material is then treated with dilute hydrochloric acid at low temperatures, to release the mineral content. The demineralised bones are neutralised to form a substance called 'ossein'. The mineral by-product - dicalciumphosphate - is a valuable fodder. ⁶

8.61 There are two gelatine manufacturing processes, depending on the type of pre-treatment used: namely, the acid process and the alkaline (basic) process. ⁷

• Alkaline pre-treatment. This process is generally used for cattle hides and for bones. The washed splits and the neutralised ossein are treated for up to six months with lime milk. This loosens the cross-links of the connective tissue. The material is then washed and neutralised, and any salts produced are washed out by changing the water up to 20 times. ⁸
• Acid pre-treatment. This method is generally used for pigskins, in which the skin is not so strongly cross-linked and extractability can therefore be achieved more readily. They are treated with acid for one day, followed by neutralising and washing out of the salts by changing the water several times. This method is far quicker and cheaper. ⁹

8.62 The gelatine is then extracted from the materials produced by these pre-treatment processes. It is dissolved out of the material by mixing with water. This is done in several stages, mixing with successively hotter water, until boiling point is reached. The gelatine produced initially by mixing with warm water has the highest gel strength. ¹⁰ The next step is purification. The gelatine solution derived during the extraction process is freed from any fat remaining from the raw materials, and from small fibres, in high speed separators. There are a number of other purification steps in which, according to the type of gelatine required, gelatine can be more-or-less completely freed from calcium or sodium ions, acid residue or other salts. The material is then filtered through cellulose plate filters. ¹¹

8.63 The final stages are concentration and drying. The gelatine solution is sterilised by ultra-heating followed by multi-stage vacuum evaporation. The water is gently removed, and the gelatine is concentrated to a honey-like consistency. The viscous solution obtained is then passed again through cellulose plate filters, which are capable of removing even the finest suspension particles. ¹² The concentrated solution is subjected to a further ultra-heat-treated (UHT) sterilisation cycle, and then cooled and solidified in a freezer. The gelatine is then dried, before being ground to uniform-sized granules. It is ground, sifted and mixed to suit specific applications. ¹³

8.64 Processing from hides is relatively mild, but the subsequent extraction procedures are likely to cause substantial removal and deactivation of the BSE agent if it is present in the source material. Indeed, the BSE Working Party of the Committee on Safety of Medicines considered that gelatine could be listed in the lowest risk category of bovine-derived material. ¹⁴ However, as SEAC noted, there was no guarantee that the source material had been kept separate from bovine brain and spinal cord, if it had come from countries with known BSE cases or the prospect of BSE.

8.65 Commission Decision 94/381/EC of 27 June 1994 prevented gelatine derived from ruminants being fed to ruminant species. ¹⁵ The EU Scientific Veterinary Committee subgroup on BSE assessed gelatine, and concluded that the risk from trading gelatine for technical use was negligible, regardless of the tissue source. This advice was accepted by the EU, and the subsequent Commission Decision 95/60/EC ¹⁶ excepted gelatine from the general prohibition of feeding ruminants any ruminant-derived protein, as imposed by Decision 94/381/EC. ¹⁷ Gelatine is further discussed in Volume 11: Scientists after Southwood.