Study On Anti-oxidative Effect And Anti-free Radical Activity Of Rosemary Extract On Fish Oils

In this thesis, fish oil is extracted from the waste out of tilapia. Firstly, using the measurement method of over-peroxide value, choose a better oxidation resistance antioxidants from phospholipids, natural vitamin E and gallic acid forming a complex matter with rosemary extract.In order to obtain the rosemary complex antioxidant of stronger antioxidant activity for fish oil. Next, using the conjunction technology of thermal gravimetric analysis (TG) and differential scanning calorimetry (DSC). The effects of rosemary antioxidant mixture on the thermal oxidation characteristics and activation energy of fish oil was studied from three areas such as the heating rate, the atmosphere and the oxidation induction time. Finally, to study the role of free radicals by antioxidants in two ways.Spectrophotometric to analyze the DPPH radical added into the fish oil and paramagnetic resonance (EPR) to directly detect fish oil free radicals. The experiments has a certain reference value on storage of grease,improvement of antioxidants and investigate the relationship between lipid oxidation and free radicals. The results are as follows:1.. Over-peroxide value analysis. Rosemary extract and other three natural antioxidants has some antioxidant activity on fish oil. Among them, the natural vitamin E’s antioxidant capacity for fish oil depending on the amount of its added. When soy lecithin’s added amount was increased from 0.05% to 0.15%, its pro-oxidative capacity weakened. Further enhance the added scale exhibited antioxidant activity. Rosemary and gallic acid’s antioxidant effect on fish oil is better than the first two, and their antioxidant capacity are proportional to the concentration. At the same concentration, the antioxidant activity of rosemary for fish oil is higher than gallic acid. Effects of single antioxidants in general is not stronger than complex antioxidant, their complexation produced significant synergies. When 60% of rosemary and 40% of gallic acid were complexed, and their complexation dosage was 0.025%, the antioxidant effect is best.2、TG-DSC-MS Analysis. Different atmosphere has great effects on both TG and DSC curves of fish oil. when the heating rates were used 10,20,40K/min for the same oil, with the increasing of heating rate, the oxidation peak moved to the high temprature and peak shape became large and sharp. When the atmosphere was nitrogen, DSC curves without heat peaks. The same kind of conditions, exothermic peak of oxygen atmosphere is bigger than air atmosphere. TG curve shows that fish oil without antioxidant added in an oxygen atmosphere weightless at 234℃, followed by an atmosphere of air at 256℃, while under a nitrogen atmosphere it began weight loss at 352℃, and the final weight loss curve completely overlap,which means the higher the oxygen concentration, oil more easily oxidized. The antioxidant helps improve the initial oxidation temperature of the fish oil and extend fish oil oxidation induction time, thereby enhancing the oxidation stability.3、Spectrophotometry and EPR analysis. Blank sample’s starting absorbance was significantly higher than the sample with antioxidants, indicating that antioxidant has an effect on clearing free radical. Compared with synchronous POV map, further prove that antioxidants scavenging free radicals to achieve the purpose of anti-oxidation. EPR analysis using the spin trap agent PBN to trap fish free radicals. Rosemary belongs to chain scission type antioxidants, it can react with aliphatic radical or alkoxy radical to prevent the spread of the chain.In the homeostasis of little molecule radicals colliding to form macromolecular radicals, the rosemary hinder this process. Under the same heating time, the higher the temperature, the higher the content of free radicals. In the case of a large number of free radical formation, rosemary shows its anti-free radical advantage.