Understanding and Management of Browning in Fresh Whole and Lightly Processed Fruits

Browning is the result of appearance of dark colored pigments formed by enzymatic and non enzymatic reactions. In this review AA, first overview the biochemistry of browning and fruits response and protection, successively touch the topic in the lightly processed fruits. Non enzymatic reaction is mainly due to Maillard reaction compounds in which concentration of amino acid (nitrogen supply) and sugars content plays the important role. Enzymatic reaction is driven mainly by polyphenols oxidase (PPO) but PPO is not the only factor, indeed the decline in the concentration of some browning activators, such as fatty acids and organic acids, and a decrease in phenolic substrate synthesis with increasing ripening, could be even important. Other enzymes are involved in the browning process, more or less intensively, depending on the product. The action of PPO as well as the other enzymes is favoured by membrane degradation which permits the contact between the enzymes and the substrate (PPO and phenols). Thus, every factor affecting membrane layers stability will result in a browning symptom. In some cases, anoxic conditions for short time prevent the appearance of browning because of reduction energy available, or because of the formation of ethanol and acetaldehyde. Carbon dioxide can inhibit browning but it can accelerate. 1-methylcyclopropene, ethylene action inhibitor, can inhibit superficial scald in apple but even provokes browning (greyish peel) in banana. In conclusion there is no prevention action against browning which can be recommended totally safe because the system is very complex and affected from many factors. _____________________________________________________________________________________________________________