EFFECT OF CARBON DIOXIDE ON THE INACTIVATION OF 

 PLANT AND CRUSTACEAN POLYPHENOL OXIDASES 



Introduction 



Undesirable enzymatic browning caused by polyphenol oxidase (E.C. 

 1.14.18.1; PPO) on the surface of food products has been of great concern 

 to food scientists and food processors since the melanin formed reduces 

 the consumers' acceptability of these products. Many chemicals have been 

 studied extensively for their effectiveness in inhibiting PPO activity 

 (Jones et al.. 1965; Mayer et al . , 1964; Palmer and Roberts, 1967; Walker, 

 1975; Madero and Finne, 1982; Golan-Goldhhirsh and Whitaker, 1984; 

 Sayavedra-Soto and Montgomery, 1986; Ferrer et al . , 1989b; Chen et al . , 

 1991b) and shown to effectively inhibit melanosis of fruits, vegetables, 

 and crustaceans. However, problems related to off-flavor, off-odor,' 

 toxicity, and economic feasibility affect the application of these 

 compounds (Eskinetal., 1971). . > 



A modified atmosphere with carbon dioxide has been used as a! 

 physical application to affect many enzyme activities (Parkin and Brown, 

 1982; Gee and Brown, 1978a, b), including the inhibition of PPO and thus 

 the prevention of discoloration in fruits and vegetables (Kader et al . , 

 1973). Supercritical (SC) fluids exhibiting physicochemical properties 

 intermediate between those of liquids and gases has been reported by 

 several workers for its inactivation of peroxidase (Christianson et al . , 

 1984), PPO (Zemel, 1989), and pectinesterase (Arreola, 1990) when carbon 



