Colour retention agents

Erythorbic acid and sodium erythorbate may be used for preserved and semi-preserved fish products and frozen and deep-frozen fish at a concentration of 1500 mg/kg. The amount of these antioxidants allowed for preservation of cured and preserved meat products is only 500 mg/kg (expressed as erythorbic acid). The use of 4-hexylresorcinol (4-hexyl-1,3-benzenediol) is permitted up to 2 mg/kg as a colour retention agent for treatment of crustacean meat (fresh and frozen), namely to prevent black spots arising by enzymatic browning reactions, known as shrimp melanosis. 

Water-insoluble pigments have a somewhat limited, but nonetheless essential, part to play in the colouration of certain papers. They are normally applied as anionic dispersions. They have virtnaUy no affinity for ceUulosic fibres and instead rely upon either mechanical retention from the paper machine itself or flocculation via a cationic product (fixing agent) to produce small floes which can be retained on the fibre snrface. 

Many of the so-called engineering thermoplastics retain their outstanding physical properties well after external exposure, if properly compounded with stabilizers, carbon black, UV agents, and so on [39]. Retention of colour and surface gloss is more problematical and protection with a surface coating is often required, film laminating and metallization being alternatives to conventional types. 

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