A. 



. 'W 



INHIBITION MECHANISM OF KOJIC ACID ON SOME PLANT AND 

 CRUSTACEAN POLYPHENOL OXIDASES 



Introduction 



Unfavorable darkening of many food products resulting from enzymatic 

 oxidation of phenols to orthoquinones by polyphenol oxidase (PPO, E.C. 

 1.14.18.1) has been of great concern to food technologists and processors 

 (Joslyn and Ponting, 1951). The darkening of food products, although 

 innocuous to consumers, causes a decrease in market value and economic 

 loss because it connotes spoilage. - 



Enzymatic browning of plant products and crustaceans due to PPO 

 activity has been widely studied (Bailey et al . , 1960a, 1960b; Ferrer et 

 al., 1989a; Flurkey and Jen, 1978; Harel et al . , 1966; Ogawa et al . , 1984; 

 Walker, 1962, 1964). Compounds capable of inhibiting melanosis in these 

 products through the interference of PPO mediated reactions or through the 

 reduction of orthoquinones to diphenols have been identified (Bailey and 

 Fieger, 1954; Ferrer et al . , 1989b; Golan-Goldhhirsh and Whitaker, 1984; 

 Harel et al., 1967; Madero and Finne, 1982; Palmer and Roberts, 1967; Robb 

 et al., 1966; Sayavedra-Soto and Montgomery, 1986; Wagner and Finne, 1984; 

 Walker, 1975, 1976). However, the number of chemicals that can actually 

 be used in food systems to inhibit melanosis is limited due to off- 

 flavors, off-odors, toxicity, and economic feasibility (Eskin et al . , 

 1971). 



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