until the point has been settled. In this connec- 

 tion, it might be noted that a recent report 

 (Rossi-Fanelli and Antonini 1955) cites work 

 in which myoglobin was separated from tuna 

 flesh giving a connpound differing from the 

 corresponding compound found in mammalian 

 flesh. No details of this difference were given. 



PIGMENT DERIVATIVES PRESENT 

 IN TUNA FLESH 



As has been previously noted (Naughton, 

 Frodynna, and Zeitlin, 1956), extraction of raw 

 flesh gave a colored solution tentatively iden- 

 tified as being largely met- or ferric myoglobin. 

 When reflectance measuring techniques were 

 brought to bear on the problenn, it became evi- 

 dent that the raw meat used in these studies 

 contained a mixture of oxy- and metmyoglobin. 

 Examples of the reflectance curves obtained 

 can be seen in figure 4. 



500 550 600 



WAVE LENGTH, M/J 



500 550 600 



WAVE LENGTH, M/J 



>- 

 CJ 



IT 

 O 



< 



450 500 550 600 

 WAVE LENGTH, M/J 



650 



700 



Figure 4. --Reflectance curves showing pigment 

 mixtures found in raw tuna flesh, (a) Largely 

 oxymyoglobin. (b) Largely metmyoglobin. 

 (c) Mixture of met- and oxymyoglobin. 



Figure 5.--A. Simplified absorption curve 

 showing increased concentration of methe- 

 moglobin in mixtures with oxyhemoglobin 

 increasing from curve (a) to (d). (From 

 Austin and Drabkin 1935-36) B. Similar 

 simplified absorption curves taken in reflec- 

 tion for tuna meat after various periods of 

 freezer storage, showing increased nnetmyo- 

 globin content, (a) Fresh tuna (sep. sample), 

 (b) After 24 hours' freezer storage, (c) 

 After 36 hours' freezer storage, (d) After 84 

 hours' freezer storage, (e) After complete 

 conversion to metnnyoglobin by chemical 

 oxidation. 



in a similar fashion the changes in absorption 

 obtained by Austin and Drabkin (1935-36) for 

 mixtures of oxyhemoglobin and methemoglobin 

 of known content. 



Deoxygenation of Oxymyoglobin 



PIGMENT CHANGES IN RAW FLESH 



Oxymyoglobin to Metmyoglobin 



With the continuation of the measurements 

 on raw meat, it became evident that we were 

 dealing with apignnent system that was extremely 

 changeable and evanescent. It was possible to 

 recognize rather rapid oxidative deterioration 

 in meat even when held under refrigeration. An 

 example involving the change from oxymyoglobin 

 to metmyoglobin can be seen in figure 5. That 

 the change corresponds to an increase in metmyo- 

 globin content can be verified by comparison 

 with the "A" portion of figure 5, which shows 



An attempt to bring about the reduction of 

 oxymyoglobin to nnyoglobin by successive eva- 

 cuation and purging with inert gas (nitrogen)--a 

 technique that works well with oxyhemoglobin in 

 blood--resulted in a more rapid conversion to 

 metmyoglobin (figure 6). This rather surprising 

 behavior may result from the very active form 

 of oxygen released in situ in the flesh, which 

 readily oxidizes the ferrous iron in the myoglo- 

 bin to the ferric fornn in metmyoglobin. Lemberg 

 and Legge (1949, p. 395) have discussed a simi- 

 lar reaction for hennoglobin in the presence of 

 proton donors. The implications of this reaction 

 in the greening of tuna flesh will be discussed 

 subsequently. 



