content and rancid ancid ancid ancid ancid off-odor and overall smell intensities in the dark muscle. The rate of lipid oxidation of the yellowtail dark muscle off-odor and overall smell intensities in the dark muscle. The rate of lipid oxidation of the yellowtail dark muscle off-odor and overall smell intensities in the dark muscle. The rate of lipid oxidation of the yellowtail dark muscle off-odor and overall smell intensities in the dark muscle. The rate of lipid oxidation of the yellowtail dark muscle off-odor and overall smell intensities in the dark muscle. The rate of lipid oxidation of the yellowtail dark muscle was significantly faster than that of the ordinary muscle. Lipid oxidation of the dark muscle was closely related was significantly faster than that of the ordinary muscle. Lipid oxidation of the dark muscle was closely related was significantly faster than that of the ordinary muscle. Lipid oxidation of the dark muscle was closely related was significantly faster than that of the ordinary muscle. Lipid oxidation of the dark muscle was closely related was significantly faster than that of the ordinary muscle. Lipid oxidation of the dark muscle was closely related to meat darkening and development of the rancid off-odor during the early stage of ice storage. to meat darkening and development of the rancid off-odor during the early stage of ice storage. to meat darkening and development of the rancid off-odor during the early stage of ice storage. to meat darkening and development of the rancid off-odor during the early stage of ice storage. to meat darkening and development of the rancid off-odor during the early stage of ice storage.

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A flow injection analysis (FIA) system coupled with a fluorescence detection system using diphenyl-1-pyrenylphosphine (DPPP) was developed as a highly sensitive and reproducible quantitative method of total lipid hydroperoxide analysis. Fluorescence analysis of DPPP oxide generated by the reaction of lipid hydroperoxides with DPPP enabled a quantitative determination of the total amount of lipid hydroperoxides. Use of 1-myristoyl-2-(12-((7-nitro-2-1,3-benzoxadiazol-4-yl)amino) dodecanoyl)-sn-glycero-3-phosphocholine as the internal standard improved the sensitivity and reproducibility of the analysis. Several commercially available edible oils, including soybean oil, rape-seed oil, olive oil, corn oil, canola oil, safflower oil, mixed vegetable oils, cod liver oil, and sardine oil were analyzed by the FIA system for the quantitative determination of total lipid hydroperoxides. The minimal amounts of sample oils required were 50 microg of soybean oil (PV = 2.71 meq/kg) and 3 mg of sardine oil (PV = 0.38 meq/kg) for a single injection. Thus, sensitivity was sufficient for the detection of a small amount and/or low concentration of hydroperoxides in common edible oils. The recovery of sample oils for the FIA system ranged between 87.2+/-2.6% and 102+/-5.1% when PV ranged between 0.38 and 58.8 meq/kg. The CV in the analyses of soybean oil (PV = 3.25 meq/kg), cod liver oil (PV = 6.71 meq/kg), rapeseed oil (PV = 12.3 meq/kg), and sardine oil (PV = 63.8 meq/kg) were 4.31, 5.66, 8.27, and 11.2%, respectively, demonstrating sufficient reproducibility of the FIA system for the determination of lipid hydroperoxides. The squared correlation (r2) between the FIA system and the official AOCS iodometric titration method in a linear regression analysis was estimated at 0.9976 within the range of 0.35-77.8 meq/kg of PV (n = 42). Thus, the FIA system provided satisfactory detection limits, recovery, and reproducibility. The FIA system was further applied to evaluate changes in the total amounts of lipid hydroperoxides in fish muscle stored on ice.

The present study investigated the effects of lipid oxidation on quality deterioration in the ordinary and dark muscles of skipjack tuna Katuwonus pelamis during the early stages of ice storage for 72 h. The lipid hydroperoxide content of the dark muscle was significantly higher (P \ 0.01) than that of the ordinary muscle throughout 72 h of ice storage. The metmyoglobin content of the ordinary muscle gradually increased, and was accompanied with darkening in the fish meat color. On the other hand, the addition of sodium ascorbate or 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox Ò ) to the ordinary muscle of skipjack tuna significantly inhibited the formation of lipid hydroperoxide as well as metmyoglobin formation. Thus, a decrease in a-tocopherol content in the ordinary muscle with antioxidant addition was not observed during ice storage period. In conclusion, the rate of lipid oxidation of skipjack tuna ordinary muscle is closely related to metmyoglobin formation, and the addition of antioxidants to fish meat is effective at inhibiting lipid oxidation as well as myoglobin oxidation in post-mortem meat.

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