Browning Reactions in Foods

Abstract

AbstractFood products undergo enzymatic and non-enzymatic browning due to reactions among amino acids and proteins with simple/complex carbohydrate, oxidized phenolic clusters, and oxidized fats/lipids leading to deterioration during processing and storage. Enzymatic browning occurs in fruits and vegetables when exposed to atmosphere during physical abrasions. Enzymes viz., polyphenol oxidase (PPO) and peroxidase (POD) are mainly responsible for this type of browning. PPO catalyzes the oxidation of the functional –OH group linked to the carbon atom of the benzene ring of monohydroxy phenols and dehydrogenation of o-dihydroxy phenols to o-quinones. The oxidation of phenolic compounds to quinones and the formation of melanin give dusky color to the foods. The POD uses H2O2 as a catalyst for the oxidation of phenolic compounds. The POD is allied to undesirable changes in flavor, texture, color, and the nutritional efficacy of foods. The level of PPO and POD varies in fruit and vegetable, and its content changes with maturity and senescence dependent upon the ratio of bounded and soluble enzymes. Non-enzymatic browning consists of a varied number of reactions such as Maillard reaction, chemical oxidation of phenols, maderization and caramelization. Possible methodologies to inhibit these browning reactions during food processing are described in this chapter.