I 



form brown pigments or melanins (Joslyn and Ponting, 1951). Enzymatic 

 browning of fruits, vegetables, and seafood products (mainly shrimp and 

 lobster) due to PPO activity has been extensively studied (Ferrer et al . , 

 1989a; Flurkey and Jen, 1978; Harel et al . , 1966; Koburger et al . , 1985; 

 Macrae and Duggleby, 1968; Madero and Finne, 1982; Mapson et al.,1963; 

 Mosel and Hermann, 1974; Palmer, 1963; Patil and Zucker, 1965; Savagaon 

 and Sreenivasan, 1978; Sciancalepore and Longone, 1984; Simpson et al , , 

 1987, 1988a; Walker, 1962, 1964; Weurman and Swain, 1955). Although not 

 harmful to consumers, it is the formation of melanins on the surface of 

 these products by PPO that decreases their market value, making them 

 unappealing and the perception of spoilage (Alford and Fieger, 1952; 

 Bailey and Fieger, 1954; Bailey et al . , 1960a, 1960b; Faulkner et al . , 

 1954; Ogawa et al., 1984). 



Inhibition/Prevention of Melanosis 



Undesirable enzymatic browning occurring in agricultural products 

 causes an enormous economical loss for food industries. Thus, in order to 

 reduce this loss, the occurrence of melanosis on food products must be 

 prevented or inhibited. Inhibition of PPO and prevention of enzymatic 

 browning are often treated as one and the same subject. Browning can be 

 prevented by inactivating PPO, by eliminating one of the substrates 

 necessary for the reaction (Oj and the polyphenols), or by reacting the 

 products of PPO metabolism which in turn inhibit the formation of the 

 colored compounds produced in the secondary, non-enzymatic reaction steps. 

 As PPO is a metal loprotein with copper as the prosthetic group (Bailey et 

 al., 1960a; Bendall and Gregory, 1966; Mayer, 1962; Smith and Kruger, 



