Sulfite , enzymatic browning

Salads. A combination of citric acid and ascorbic acid is used as an alternative to sulfites in prevention of enzymatic browning in fresh prepared vegetables (56). 

Sulfites and Ascorbic Acid as Browning Inhibitors. Historically, enzymatic browning was controlled by the application of sulfites... 

Studies reviewed herein have demonstrated the potential ability of several new approaches to control enzymatic browning in fruit and vegetable products the use of novel AA derivatives, polyphosphates and (5-cyclodextrin as browning inhibitors the application of browning inhibitors to cut fruits and vegetables by pressure infiltration and the use of cvs. having a low tendency to brown. It is likely that one or more of these approaches will be useful as an alternative to sulfites to control browning in affected commodities. 

Lambrecht, H.S. Sulfite substitutes for the prevention of enzymatic browning in foods, in Enzymatic Browning and Its Prevention, Lee, C.Y. and Whitaker, J.R., Eds., American Chemical Society, Washington, DC, 1995, p. 313. 

Reaction of amino groups of amino acids, peptides, and proteins with carbonyl groups of carbohydrates or with tyrosine-derived quinone groups encompass changes respectively called nonenzymatic and enzymatic browning reactions (57-75). Such changes may adversely affect the appearance, taste, nutritional quality, and safety of many foods. Until recently, sodium sulfite has been used to inhibit browning... 

Losses during the cooking of root vegetables are usually around 25% and in leafy vegetables are about 40%. The addition of sulfites, used to prevent enzymatic browning reactions in peeled potatoes or dried fruits and vegetables, results in extensive or total destruction of thiamine. 

Substances with reducing effects are sulfur dioxide and sulfites, which are also used as preservatives, inhibitors of enzymatic browning reactions and inhibitors of non-enzymatic browning reactions. The bleaching activity is mainly based on their ability to reduce the primary products of enzymatic browning reactions - quinones, whose subsequent reactions would otherwise lead to undesirable discoloration in dried fruits, vegetables, potatoes and other products. Furthermore, these compounds are used for the bleaching of hops, lecithin concentrates, mushrooms, nuts and fish products. 

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