Citric acid discoloration prevention

Paper. Citric acid is added to the pulp slurry prior to bleaching to sequester metal ions and prevent discoloration (208—211). Citrates are used in cigarette paper to control the burning rate to match that for tobacco. 

Cosmetics and Toiletries. Citric acid and bicarbonate are used in effervescent type denture cleansers to provide agitation by reacting to form carbon dioxide gas. Citric acid is added to cosmetic formulations to adjust the pH, act as a buffer, and chelate metal ions preventing formulation discoloration and decomposition (213—218). 

In irradiated potatoes, especially in some varieties and as a function of cultivating conditions of the raw material, after-cooking darkening may occur. This discoloration is attributed to formation of ferric-phenolic complexes. This phenomenon depends on the iron content, and is related to increased polyphenol formation and reduced citric acid levels, which are influenced by agronomic and climatic factors. Various technological measures have been developed to prevent this after-cooking darkening [23]. 

BHA Antioxidant (0.01% w/v) Prevents oxidation of fats and oils and is frequently used in combination with BHT or citric acid. Trace quantities of metals and exposure to light cause discoloration and loss of activity... 

Chelation. Chelating agents, such as EDTA, are added to prevent precipitation of insoluble metal salts. Citric acid and tartaric acid are other chelating agents that are added to prevent discoloration during food processing. 

Food acidulants find their application, for the greater part, in beverages and in fruit and vegetable processing. Apart from pH lowering, acidulants provide buffer capacity, impair sourness and tartness, enhance the effect of preservatives, and for some acidulants such as citric acid, prevent discoloration caused by trace metals (Seifert, 1992). 

Ascorbic acid acts as both an antioxidant and a pro-oxidant. Appropriate levels for preventing muscle discoloration are, therefore, dependent on a number of factors, such as the presence and concentration of metals within a food (Mancini et al., 2007). Ascorbic acid s pro-oxidant action could also be attributed to the production of ferrous heme proteins, which may be more reactive and more oxidative than ferric derivatives (Yamamoto, Takahashi, and Niki, 1987). The addition of citric acid as chelator may improve the efficacy of ascorbic acid in muscle food (Mancini et al., 2007). 

---