FISHERY BULLETIN: VOL. 80. NO. 2 



After testing for inhibition effects in the 

 (model) blended system, tests were conducted on 

 ground (minced) parasitized Pacific whiting to 

 test those which demonstrated inhibitory 

 potential and could be used in food systems. 



Hydrogen Peroxide 



In the ground parasitized Pacific whiting, 

 hydrogen peroxide was significantly less effec- 

 tive in inactivating the proteolytic enzyme than 

 it had been with the blended fish. This was 

 explained by the fact that catalase is known to be 

 present in muscle to destroy hydrogen peroxide 

 formed in aerobic muscle fiber (Deisseroth and 

 Dounce 1970). There was a difference between 

 the blended and ground muscle both in protein 

 concentration and distribution of the catalase. In 

 order to demonstrate the difference more specif- 

 ically, we compared the protein concentration 

 and the catalase activity in the two systems. Pro- 

 teins were determined by the macro-Kjeldahl, 

 percent protein N method. Catalase activity was 

 determined by measuring the disappearance of 

 peroxide residues after 0.3% H2O2 (0.146 meq) 

 was mixed with 1 g of blended or ground fish. The 

 results in Table 2 show 40% less protein, which 

 includes catalase, in blended fish than in ground 

 fish. When 0.3% H1O2 was added to the blended 

 fish, hydrogen peroxide was more slowly de- 

 graded and thereby had longer contact time with 

 the enzyme of the parasite. The location of the 

 catalase was shown by washing out all intercel- 

 lular catalase from ground muscle, then ^in- 

 stituting the catalase activity by crushing or 

 manipulating the washed muscle fibers. A con- 

 centration of 3% H 2 2 was needed to counteract 

 all catalase activity, but a concentration of this 

 magnitude also destroyed the tissue structure. It 

 was obvious that hydrogen peroxide alone would 

 be impractical to use as a protease inhibitor. 



Potassium Bromate 



Because of the difference in protein concentra- 

 tion in ground fish, it was necessary to increase 

 the concentration of potassium bromate from 



Table 2.— Comparison of protein concentration and peroxide 

 residues in blended or ground parasitized Pacific whiting. 



0.01% to 0.05% in order to achieve a 63-66% in- 

 hibition of proteolytic activity. This was shown to 

 be sufficient to maintain the texture of para- 

 sitized Pacific whiting. 



Tsen (1968) suggested that there was a syn- 

 ergistic effect between potassium bromate, a 

 slow oxidizer, and faster oxidizers such as 

 iodates, acetone peroxide, or azodecarbonamide; 

 therefore, potassium bromate was tested with 

 hydrogen peroxide in varying concentrations. 

 The results were not synergistic but 0.025% 

 KBr0 3 with 0.5% H2O2 was as effective as 0.05% 

 KBr0 3 (Table 3). 



Table 3.— Effect of hydrogen peroxide and 

 potassium bromate on proteolysis in ground 

 parasitized Pacific whiting. 



Dibasic Phosphate Peroxides 



The adduct of hydrogen peroxide with dibasic 

 phosphates has been found to facilitate the use of 

 hydrogen peroxide by stabilizing it in food sys- 

 tems (Pintauro 1974). It seemed possible that 

 these compounds might protect hydrogen perox- 

 ide from catalase long enough for it to be effective 

 in inhibiting proteolysis. We tested 0.3% and 0.5% 

 of both disodium phosphate peroxide (Na2HPCv 

 H2O2) and dipotassium phosphate peroxide 

 (K2HPO4H2O2) with ground parasitized Pacif- 

 ic whiting. When these compounds were 

 compared in terms of milliequivalents of perox- 

 ides with equivalent concentrations of hydrogen 

 peroxide alone, disodium phosphate peroxide 

 had 23% milliequivalents of peroxide and dipo- 

 tassium phosphate peroxides 15%. The dipotas- 

 sium phosphate peroxide seemed less stable than 

 disodium phosphate peroxide judging from its 

 effervescence. Both dibasic phosphate peroxides 

 were tested alone and with potassium bromate 

 (Table 4). As found earlier in combination with 

 hydrogen peroxide, 0.025% KBr03 enhanced the 

 proteolytic inhibition of both concentrations of 

 dibasic phosphate peroxides which meant effec- 

 tive inhibition could be achieved with lower con- 

 centrations of each of the oxidants. 



The results of testing these inhibitors estab- 

 lished concentrations and combinations which 



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