100 r-l^ 



y 80 



o 



1^ 60 - 



U- 



UJ I— 



(r 



^ 40 



LU 

 O 



q: 



LlI 

 Q. 20 



LABORATORY COOK 

 COMMERCIAL COOK 



O"-!-^ 



J L 



J L 



J L 



400 440 480 520 560 600 

 WAVE LENGTH (M\l) 



640 



680 



Figure 5. --Reflectance of cooked normal tuna prepared in the laboratory 

 and commercially at Hawaiian Tuna Packers, Ltd. 



in meat tissue, would be present, and this, in 

 fact, has been reported inalbacore by Matsuzaka 

 and Takahashi (MS.). Moreover, myoglobinhas 

 beenreported in the red blood meat offish flesh 

 by other investigators (Mondovi and Antonini 

 1955). In the species of tuna (yellowfin), under 

 investigation in this study, the evidence seems 

 to point to similar pigments or their derivatives 

 being involved, despite the fact that earlier 

 studies of the properties of the pigment led us 

 to suspect a peroxidase-like heme protein. 



Part of the work on this project involved an 

 attempt to extract pigments from tuna flesh. A 

 futile effort was made to obtain green substances 

 of the verdohemochrome type from the green 

 meat. In the case of raw meat it was found pos- 

 sible with aqueous or dilute alcoholic solvents 

 to obtain an extract that contained much of the 

 pigment of the meat. The final simplified pro- 

 cedure settled on was essentially that of Husaini 

 et al. (1950), and involved blending and extraction 

 with a dilute carbonate solution. Other solvents, 

 such as alcohol and glacial acetic acid, extracted 

 pignnents which seemed to be altered products 

 (probably by denaturation or cleavage) of the 

 pigments present in the flesh. No success was 

 achieved in extracting pigments from cooked 

 meats. 



Close examination of the spectophotometric 

 curves of the pigment extracted from raw flesh 



shows it to be the ferric oxidized form of 

 hemoglobin or myoglobin ( methemoglobin 

 or metmyoglobin). This is easily reducible to 

 the ferrous form. Further work is under way 

 through derivative formation to establish whether 

 hemo- or myoglobin is involved, with the greater 

 probability favoring the latter, judging from the 

 findings of the Japanese workers. 



CHANGES IN PIGMENT PRODUCING GREENING 



In order to elucidiate the mechanism or reason 

 for greening, attempts were made to fractionate 

 the pigmented mixture extracted from green and 

 normal raw tuna flesh. Use was made of ammo- 

 nium sulfate fractionation and filter paper electro- 

 phoresis, both without success to date. Extrac- 

 tion studies seem to show the presence, or the 

 extractability, of a larger amount of methemo- 

 or metmyoglobin from green meat than from 

 normal. Reflectance studies also are in agree- 

 ment with this since a lesser degree of reflect- 

 ance seems to be indicated for the average green 

 than for the average unbr owned normal tuna 

 flesh, showing a higher concentration of the 

 absorber or pigment. Certain nornnal samples 

 do show an abnormal pinkness with high pigment 

 concentration (e. g. , No. 6, fig. 4). Further 

 work is under way to separate more positively 

 the factors of browning and greening, and to show 

 the relationship, if any, between the two. 



