Doctor of Philosophy (PhD)


School of Nutrition and Food Sciences

Document Type



Antioxidant capabilities of the spice extract of ginger, oregano, rosemary and turmeric were evaluated by monitoring inhibition of DHA and EPA in a menhaden fish oil model and cholesterol oxidation model system. The spice extracts were mixed with the fish oil at 1, 2.5 and 5 % (w/w) and 1, 2.5 and 5mg (dw) were used in cholesterol study. The temperatures 150oC and 175oC were used for the oxidation study and a 60oC was used for incubation storage. The methanol extracts of all four spices demonstrated significant capability in retaining the DHA and EPA, after subjected to oxidation when compared with the control. The oregano retained 66% and 41% of DHA for 5 % at 150 and 175 oC respectively. For the 60oC storage study, at the end of the 6 day period, rosemary extract showed the highest retention of 84% DHA at 2.5%. For the cholesterol oxidation study, at 150oC, 2.5 mg extract retained 83, 81, 73 and 87 % cholesterol for ginger, oregano, rosemary and turmeric respectively. At 175oC, all the spice extracts were still significantly effective in retaining cholesterol as compared with the control and the antioxidant capabilities in decreasing order were oregano > rosemary > ginger > turmeric. For the antioxidant and total phenolic study, without heating, the antioxidant activity (TEAC) values ranged from 0.18 to 0.60 µmol of trolox equivalent/gm of extract, with oregano the lowest and rosemary showing the highest activity. After heating, the antioxidant activity declined for all the spice tissues. During the 60oC incubation storage, only rosemary demonstrated a 10 % increase in the antioxidant capability. The result for total phenolic content values in decreasing order were turmeric > rosemary > ginger > oregano. With heating at both 150 and 175oC, turmeric, rosemary and oregano showed no significant reduction in phenolics. The storage study showed a uniform decrease in the total phenolic content for all the spices and turmeric demonstrated highest values. Thus the spice extracts of ginger, oregano, rosemary and turmeric demonstrated significant antioxidant capability by retaining DHA and EPA in menhaden fish oil and cholesterol during oxidative degradation.



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Committee Chair

Zhimin Xu



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Life Sciences Commons