46G-18 |
Oxymyoglobin and lipid oxidation in yellowfin tuna (Thunnus albacares) loins |
S. LEE1, S. Joo2, A. L. Phillips1, and C. Faustman1. (1) Department of Animal Science, University of Connecticut, 3636 Horsebarn Hill Road Ext., U-4040, Storrs, CT 06269-4040, (2) Division of Animal Science, Gyeongsang National University, ChinjuSi, GajoaDong 900, Chinju, 660-701, South Korea The relationship between oxymyoglobin (OxyMb) stability and lipid oxidation is well established in beef but not other species. Tuna myoglobin appears to oxidize faster than mammalian myoglobins (Mb) and this may be related to its different amino acid composition. Our objectives were to characterize OxyMb and lipid oxidation in yellowfin tuna, and to determine the influence of various aldehydes on tuna OxyMb stability in vitro. Steaks (2.5 cm) and ground muscle patties were prepared from 8 loins and stored on ice under refrigeration in the dark. Surface metmyoglobin (MetMb) accumulation, Hunter L*, a*, and b* values, and thiobarbituric acid reactive substances (TBARS) were measured at 0, 1, 3, and 6 days. Tuna OxyMb was prepared from loin muscle via ammonium sulfate fractionation, gel filtration, ion exchange chromatography, and hydrosulfite-mediated reduction. OxyMb was incubated in the presence of 0.1 to 1.0 mM hexanal, hexenal, or 4-hydroxynonenal (4-HNE) for 4 h at 37°C, pH 7.2; controls were aldehyde-free. Surface MetMb accumulation and lipid oxidation increased in tuna steaks with time (P<0.05). TBARS increased rapidly in tuna patties following 1 day storage (P<0.05). In both tuna steaks and patties, there were no differences in L* and b* values (P>0.05); a* values decreased during 6 days storage (P<0.05). Hue angle (tan-1 (b*/a*)*360°/2) increased with storage in both steaks and patties (P<0.05). Sensory evaluation demonstrated increased discoloration and decreased odor acceptability over time (P<0.05). Hexanal, hexenal and 4-HNE increased oxidation of tuna OxyMb relative to controls in vitro (P<0.05), and did so in a concentration-dependent manner.
Session 46G, Muscle Foods I
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