Natural pigments, deterioration with

During storage, natural pigments often deteriorate with time because of exposure to light, heat, air, and moisture or because of interaction of the components of the food with each other or with the packaging material. The color of maraschino cherries, for example, fares so poorly with storage that they are routinely bleached then artificially colored. 

Chemistry, Physics, and Biology Laboratories. As a rule, before any artifact is subjected to treatment, the chemistry laboratory determines the causes of any alterations or deterioration. The nature and structure of the artifact, its pigments and inks, are identified to avoid negative reactions to prescribed treatment. Fixatives are recommended if required these may be cellulose acetate dissolved in acetone, soluble nylon, or acrylic resin sprays. Once stains are identified, several possible solvents are selected. For deacidification, either magnesium bicarbonate or barium hydroxide usually is recommended, depending on whether an aqueous or nonaqueous solution is called for. Bleaching is discouraged, but when necessary, hypochlorites are used with suitable antichlors. 

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