168 

 at 43°C were determined to be 1.6 x 10-^ 9.4 x 10-^ and 2.5 x 10"^ min'^ 

 respectively. Under similar heating conditions in the presence of CO, (58 

 atm), the k values for brown shrimp and potato PPO were shifted to 0.98 

 and 6.9 x IQ-^min'^ Potato PPO was more resistant to the treatments than 

 lobster and brown shrimp PPO. This study also demonstrates that PPO was 

 more susceptible to the combined treatment of high pressure CO, and heat 

 than by heat alone. 



PolyacrylamidP Gel FlprtK-np hn resis of nn (I atmKt.rP.tpH 



PPO 



Only one single protein band was observed for the control and CO,- 

 treated PPO on the nondenaturing PAGE gel (Figure 37). No difference in 

 protein band position on the gel occurred among the control and CO,-treated 

 groups. The molecular weight of this protein band was assessed as 255 kD 

 which is close to the total molecular weights (277 kD) of three isoforms 

 previously reported for spiny lobster PPO (Chen et al . , 1991a). In 

 addition, it is apparent that no alteration of the intact protein molecule 

 occurred when subjected to CO, treatment. 



Mass Balance of High Pre.ssiirP m .-treated and Nnn-rn -t^^^^j^^^y^ 



Protein precipitates occurred after lobster and shrimp PPO were 

 subjected to high pressure CO, treatment. The combined protein contents 

 in the supernatant and pellet portions of the treated samples were close 

 to that of their respective untreated control (Table 10). Since CO - 

 treated potato PPO did not have a precipitate, no protein content was 

 detected in the pellet portion after centrifugation (Table 10). .. ' 



