Browning Reactions

Browning is one of the most important reactions taking place during food processing and storage. Both, enzymatic and nonenzymatic browning can affect the quality of food in either positive or negative ways, depending on the type of food. Special attention has been paid in this chapter to chemistry of the reaction. During enzymatic browning, phenolic compounds are oxidized to quinones by polyphenol oxidase, this reaction being of particular importance in fruits, vegetables, and seafoods. Nonenzymatic browning is referred to as the Maillard reaction (MR), when it takes place between free amino groups from amino acids, peptides, or proteins and the carbonyl group of reducing sugars. Ascorbic acid, its oxidation products and oxidized lipids can also react via MR. It has been also described that aminophospholipids and reducing carbohydrates can interact by MR. Food browning can be also due to degradation of carbohydrates also called caramelization reaction and it is hereby discussed.