Review: Thermal stability of carthamin bound to insoluble polymers – effects of pH and organic and inorganic compounds

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Abstract
Summary: Carthamin was adsorbed onto cellulose, cellulose derivatives, collagen and other polymers and the stability of the bound pigment examined as a function of buffer compositions, pH, the presence of metal ions or organic compounds, temperature and pressure. Free carthamin was labile, especially in aqueous solutions, while bound carthamin remained stable when heated in an oven or retort for 1h at 80‐120°C at 1.0‐2.1 atm. High buffer concentration was necessary for carthamin stability, but at high temperature and high pressure, stability greatly decreased in the presence of water. Metal ions or organic food ingredients had little effect. Basic conditions were also undesirable for preservation of the pigment on insoluble polymers. The results indicate that the bound carthamin has potential as a red‐colouring agent for some processed foods.