| Summary: | 碩士 === 國立海洋大學 === 食品科學系 === 87 === Mackerel muscle was homogenized with deionized water at a ratio of 35:70 (w/w) for 2 min and boiled for 10 min then cooled. Protease N was added to hydrolyze the homogenate at 50oC for 2h, then heated at 90oC for 10 min to stop the reaction. The supernatant obtained after centrifugation and filtration was the mackerel protein hydrolysate (MPH). The fraction molecular weight of MPH was distributed from 10 Da~178Da, 200Da, 40Da and 15Da.
In vitro studies, MPH showed inhibitory effects on lipoxygenase (LOX) catalyzed oxidation of arachidonic acid. Similar inhibitory effects were found on LOX of soybean, tilapia gill, and grey mullet gill. When MPH concentration was at or higher than 27.4~41.4 mg MPH/ g C20:4-g protein LOX extract, it had no inhibition on HPT partially purified LOX of mullet gill. MPH showed lower effect on C18:2 oxidation in comparison to that of ascorbic acid on the basis of same dry weight using hemoglobin catalyzed. HETE-Free MPH was obtained from removing with 2 volumes of ethyl acetate for 3 time, which concentration of 2.5 10-3 g/g C20:4 also inhibited the soybean LOX activity about 65 % and molecular weight was similar with MPH. When HETE-Free MPH was exposed to room temperature for 7 h before assay, it lost the inhibitory effect on LOX activity. O2 consumption rate was positive correlation with HETE produced in LOX reaction. MPH and HETE-Free MPH both has O2 consumption rate, which shows they can do oxidation byself.
Blood thinning effects were observed in-vitro by mixing MPH with red blood cell. The rheological data fit power-law model ( = n + C, where =shear stress, = shear rate, = fluid consistency, n = flow behavior index)
with a correlation coefficient R2 = 0.99 at a constant hematocrit of 35%. The addition of MPH resulted in a reduced from 0.05 to 0.01, and an increased n from 0.66 to 0.93 indicative of a flow behavior becoming closer to Newtonian type and a thinning consistency.
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