【作者】 刘书成；

【导师】 李元瑞；

【作者基本信息】 西北农林科技大学 ， 食品科学， 2002， 硕士

【摘要】 本研究以大蒜的超临界二氧化碳萃取物为研究对象，研究其对食用油脂的抗氧化性能及其抗氧化机理，并开发研制出复合型天然抗氧化剂。研究结果表明： 大蒜提取物对花生油和猪油都有一定抗氧化作用，但大蒜提取物对花生油的抗氧化作用优于对猪油的抗氧化作用，也即大蒜提取物适用于含有多不饱和脂肪酸含量高的油脂。 大蒜精油和大蒜油树脂对花生油具有比较好的抗氧化作用，且都随添加量的增加抗氧化能力增强，但在相同的添加量水平上，大蒜油树脂的抗氧化作用总是优于大蒜精油。大蒜精油添加量达0.1％时，其抗氧化能力与0.01％PG相当；当大蒜精油添加量达0.04％时，其抗氧化能力与0.02％BHT相当；当大蒜精油添加量达0.02％时，其抗氧化能力已优于0.02％BHA。而大蒜油树脂添加量达0.02％时，其抗氧化能力优于0.02％的BHA和BHT；当大蒜油树脂添加量为0.06％时，其抗氧化能力优于0.01％PG；当大蒜油树脂添加量为0.1％时，对花生油表现出很强的抗氧化作用。 贮藏温度对大蒜提取物的抗氧化作用有明显影响。高温下，油脂氧化速度加快以及大蒜提取物的不稳定作用，导致油脂的过氧化值升高较快，而在低温条件下，则可避免这些不利变化。因此，添加了大蒜提取物的油脂应尽量贮藏在低温条件下。 单独的增效剂作为抗氧化剂用于食用油脂，无论是猪油还是花生油，抗氧化效果都不明显。但与大蒜提取物复合后使用，具有明显的协同抗氧化作用，尢其是对花生油。大蒜提取物和合成抗氧化剂(BHA、BHT、PG)混合使用于花生油，都具有一定的协同抗氧化作用，尤其是与PG的混合使用。 天然复合抗氧化剂的配方经正交试验设计及分析表明，大蒜提取物是主抗氧化成份，其最佳配方是大蒜精油0.04％，Vc0.01％，柠檬酸0.02％。 根据Arrhenius方程和反应速度常数与货架寿命的关系，预测了添加大蒜提取物的花生油的货架寿命。添加了大蒜提取物的花生油的货架寿命都得到了不同程度的延长。使用0.04％精油+0.01％Vc+0.02％柠檬酸作为花生油的抗氧化剂时， 可使花生油在20’C下的货架寿命由4．3个月延长至14．5个月。 、分析探讨了大蒜提取物的抗氧化作用机理。大蒜提取物中的处于还原态的含 硫有机化合物，一方面具有很强还原性，能将过氧化物还原，表现出降低POV 的作用，而且还能与分子氧反应，降低油脂中氧浓度，从而延缓多不饱和脂肪酸 的自动氧化；另一个方面，具有清除自由基的作用，能与引起油脂自动氧化的活 泼自由基发失反应，形成新的、稳定的自由基，从而延缓多不饱和脂肪酸的自动 氧化。更多还原

【Abstract】 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.更多还原