Studies On Antioxidative Activity Of Garlic Extracts

Supercritical carbon dioxide extracts of garlic were systematically studied on antioxidative activity and mechanism in edible oils and fats. A kind of natural mixed antioxidant was developed. The results showed as follows:Garlic extracts have antioxidative activity in peanut oil and lard, and antioxidative activity in peanut oil is better than that in lard. That is to say ,garlic extracts have better antioxidative activity in oils containing more polyunsaturated fatty acids.Essential oil and oleoresin of garlic have excellent antioxidative activity in peanut oil. With the increase of their concentration, their antioxidative activity is enhanced. Moreover, antioxidative activity of garlic oleoresin is better than that of garlic essential oil in the similar concentration. Garlic essential oil(0.1%) is as active as PG(0.01%); Garlic essential oil(0.04%) is as active as BHT(0.02%); But Garlic essential oil(0.02%) is better active than BHA(0.02%). However, garlic oleoresin(0.02%) is better active than BHA(0.02%) and BHT(0.02%); garlic oleoresin(0.06%) is better active than PG(0.01%).Storage temperature has an obvious effect on antioxidative activity of garlic extracts* In higher temperature, lipids oxidation velocity is faster and garlic extracts are unstable, which results in higher lipids peroxides value. But in lower temperature, these advert conditions are avoided. Therefore, peanut oil added garlic extracts should be stored in lower temperature.Antioxidative activity is not obvious when simple synergist(vitamin C, citric acid, tartaric acid) as antioxidant is used in lipids. But synergists mixed with garlic extracts exhibit remarkable antioxidative activity and synergism in peanut oil. Synthetic antioxidants(BHA, BHT, PG) mixed with garlic extracts also exhibit remarkable antioxidative activity and synergistic effect in peanut oil.The optimized natural mixed antioxidant obtained by perpendicular experiment is as'follows: garlic essential oil(0.04%), vitamin C(0.01%), citric acid(0.02%).In terms of Arrhenius equation and the connection of reaction velocity constantand shelf life, the assurance period of peanut oil in which garlic extracts were added is predicted. When garlic essential oil(0.04%) and vitamin C(0.01%) and citric acid(0.02%) were used in peanut oil, the assurance period of the peanut oil could be prolonged from 4.3 mouths to 14.5 mouths at 20X?.In addition, antioxidative mechanism of garlic extracts was discussed in the paper. On one hand, garlic extracts have the good ability to reduce oxides, which could recover polyunsaturated fatty acids from their peroxides to a certain degree and lower peroxide value. Garlic extracts also react with oxygen, which lowers oxygen concentration hi lipids and retards automatism oxidation of polyunsaturated fatty acids. On the other hand, garlic extracts have the good ability to extinguish free radicals. They can react with active free radicals which cause oxidation of lipids and form the new stable free radicals to prevent lipids oxidation.