Novel interactions of caffeic acid with different hemoglobins: Effects on discoloration and lipid oxidation in different washed muscles

- The ability of caffeic acid to accelerate methemoglobin formation is described.
- Caffeic acid is shown to inhibit hemin dissociation from methemoglobin.
- Caffeic acid interacted differently with fish compared to mammalian hemoglobin.
- Caffeic acid stabilized the met form of perch hemoglobin in washed muscle.
- Caffeic acid prevented perch Hb-mediated lipid oxidation in washed muscle.

Caffeic acid (CA) accelerated methemoglobin (Hb) formation at pH 5.8 and 25 °C. This was attributed to electron donation from CA to liganded O2 in Hb. CA inhibited hemin dissociation from metHb. Pig Hb remained mostly as oxyHb and did not promote lipid oxidation in washed cod muscle (WCM) nor washed turkey muscle (WTM) during iced storage at pH 5.8. Conversely, perch Hb rapidly was converted to metHb and readily promoted lipid oxidation based on lipid peroxide and hexanal formation. CA strongly inhibited perch Hb-mediated lipid oxidation during storage. Once metHb formation occurred in WCM, CA appeared to maintain the heme protein as metHb during the remainder of iced storage. CA may have become bound to perch Hb based on filtration analysis. CA facilitated the transfer of perch Hb (but not pig Hb) from the aqueous phase to the insoluble components of WCM. Collectively, these results suggest that CA inhibited Hb-mediated lipid oxidation by various mechanisms not related to inhibition of metHb formation.