Lipid autoxidation in ozone‐processed crustacea under cold storage: A treatise

Polyunsaturated fatty acids (PUFAs) substantially present in decapod crustaceans, are largely responsible for the progression of lipid autoxidation that directly contribute to subsequent reduction in postharvest quality and shelflife. Even iced storage widely utilized at commercial fisheries is unable to completely slow down this deteriorative process. On the other hand, ozone usage on food as approved by US Food and Drug Administration (FDA) has over the years improved its potential applications. This is seen in recent times through the manufacture of domestic facilities that safely discharge ozone and increasingly commercially available for home use. While lipid autoxidation remains an increasing challenge to fishery product shelf life, recent studies have showed ozone treatment to be a potential preservative candidate for reducing lipid damage in a crustacean product such as shrimp.     

水份与油品质量

本文通过对水份与油品质量的关系的研究，表明水份是控制油品中非化水化磷脂含量的重要条件；适当保持油品水份可以有效地降低油脂氧化速度。     

大连葡萄汁抗氧化活性测定及误差分析

报道了利用邻苯三酚自氧化法对大连本地葡萄汁抗自由基活性的测定。通过实验研究选定检测紫外吸收波长。测试不同进样量下葡萄汁抗自由基氧化活性，结果的误差分析表明，适当的进样量可以保证测试灵敏度．降低测试偏差。活性测试结果表明，大连地区的葡萄汁具有良好的抗自由基氧化活性，适宜于功能性食品的开发。     

铜锌超氧化物歧化酶模型化合物的合成、表征及活性

模拟铜一锌超氧化物歧化酶(Cu,Zn-SOD)的活性中心,以二(2-苯并咪唑)丙烷(tbz)为桥、二(2-苯并咪唑亚甲基)胺(N3)、二(2-苯并咪唑亚甲基)甲胺(MN3)及二(2-苯并咪唑亚甲基)苄胺(BN3)为配体合成了3种异双核的小分子模型化合物,并进行了紫外、红外表征及元素分析,推测了可能的结构。采用邻苯三酚自氧化法测定了它们的生物活性,结果表明所合成的配合物具有一定的拟SOD活性。     

Cholesterol Autoxidation Inhibition Varies Among Several Natural Antioxidants in an Aqueous Model System

Inhibition of cholesterol autoxidation by several natural materials was examined in an aqueous meat model system at pH 5.50 and 80°C. Antioxidant effectiveness was measured using the induction period for 7-ketocholesterol. An industrial rosemary oleoresin, quercetin, myr-icetin and BHA (included for comparison) had no antioxidant properties for cholesterol. All tocopherol treatments delayed cholesterol oxidation. The γ- and δ- treatments were most effective and α-toco-pherol was least effective. No synergistic effects were observed with tocopherol blends. Antioxidants effective against unsaturated fatty acid autoxidation may not inhibit cholesterol autoxidation.     

Autoxidation of cod liver oil with tocopherol and ascorbyl palmitate

Cod liver oil (CLO) with no added antioxidants (REF), 200 mg/kg ascorbyl palmitate (AP), and/or 800 mg/kg tocopherol concentrate (TOH) were stored in sealed bottles with a small headspace of air at 25°C in the dark. A binary mix of TOH +AP affected the sensory perception of CLO by leading to a more grass/cucumber-like and less herring oil-like impression, whereas TOH alone had no effect. This was caused by the different influence of the antioxidants with regard to formation of volatile oxidation products. TOH+AP promoted formation of, e.g., hexanal, 2-hexenal, and 2,6-nonadienal and inhibited formation of, e.g., 2,4-heptadienal. TOH affected the proportions of trans, cis-and trans,trans-2,4-heptadienal that were formed and inhibited formation of, e.g., 1-penten-3-ol, whereas formation of acetic acid and some other volatiles was inhibited by both antioxidants. The total amount of volatiles increased during the experiment, and with REF were significantly higher (P<0.05) than with TOH. The PV increased during the first 2 wk of storage. PV levels were in the order of TOH>REF>TOH+AP. The observed effects could partly be explained by hydrogen donation from TOH to peroxyl radicals, but the mode of action for AP was unclear.     

不同饱和度的三酰甘油酯的共存对胆固醇氧化的影响

为了评价三酰甘油酯的不同饱和程度对胆固醇氧化的影响,将精制的沙丁鱼油三酰甘油酯(碘价IV=182.6)、部分氢化沙丁鱼油三酰甘油酯(IV=174.5)、全氢化沙丁鱼油三酰甘油酯(IV=92.0)分别与胆固醇混合,制成CST、CTPH和CTFH三组试样,在25℃避光处诱导其氧化。研究结果表明:试样的氧化稳定性随着上述各试样的不饱和程度的增加而降低。CST的过氧化物诱导期比CTPH的短,并且在较短的诱导期内CST中组成沙丁鱼油三酰甘油酯的高度不饱和脂肪酸(PUFA)比CTPH的明显减少。各试样中生成的主要胆固醇氧化物有7-β-羟基胆固醇、7-酮基胆固醇、β-环氧化胆固醇和胆甾烷三醇。胆固醇氧化物的生成量随着过氧化物价(POV)的变化和PUFA的减少而增加。胆固醇的氧化与共存的鱼油三酰甘油酯的自动氧化有关。尽管在胆固醇氧化物生成阶段,降低鱼油三酰甘油酯的不饱和度可有效地延缓胆固醇的氧化,但是在诱导期以后胆固醇的氧化速率与CST和CTPH中PUFA的比例无关。     

固体碱负载酞菁钴硫醇氧化催化剂的研究

将CoPc(SO3Na) 4 或CoPc[N(CH3) 3I]4 和CoPc(SO3Na) 4 二元混合物 ,负载在Mg(Al)O载体上制成的催化剂 ,能有效脱除喷气燃料中的硫醇。后者的催化活性和稳定性优于前者。Mg(Al)O负载CoPc(SO3Na) 4 催化剂运转32 4h后活性下降 ,脱硫醇率低于 60 % ,硫醇硫质量分数高于 2× 1 0 - 5;而Mg(Al)O负载二元混合物催化剂在运转4 80h后 ,脱硫醇率仍可达 85% ,硫醇硫质量分数低于 1 4× 1 0 - 5。XRD和ESR表征表明 ,前者活性下降的原因主要是Mg(Al)O载体上酞菁钴分子聚集。用带有正电荷和负电荷基团的二元水溶性酞菁钴混合物制备催化剂可在一定程度上抑制酞菁钴分子的聚集 ,改善催化剂的性能。     

E Vitamer Fraction in Rice Bran Inhibits Autooxidation of Cholesterol and Linoleic Acid in Emulsified System during Incubation

ABSTRACT: The antioxidant activities of E vitamer fraction extracted from rice bran were investigated and compared with α-tocopherol at 2 concentration levels (16 ppm and 160 ppm) in the emulsified cholesterol and linoleic acid systems. 7-Ketocholesterol, 7α-hydroxycholesterol (7α-OH), 7β-hydroxycholesterol (7β-OH), 25-hydroxycholesterol (25-OH), and 5,6-epoxycholesterol (5,6-EP) were found at different incubation times (0, 6, 12, 24, and 48 h) in the emulsified cholesterol system accelerated by using 2, 2'-azobis (2-methylpropionamidine) dihydrochloride (AAPH) at 80°C and pH 5.5. Samples treated with 160 ppm of E vitamer fraction exhibited a significant antioxidant activity by inhibiting the formation of cholesterol oxidation products (COPs). Addition of E vitamer fraction to the emulsified linoleic acid model at 37°C significantly inhibited the hydroperoxide formation and decomposition more than that of α-tocopherol. The former was more effective in inhibiting the primary and secondary oxidations of the polyunsaturated fatty acid (PUFA). No significant differences ( P < 0.05) were found in inhibition of the linoleic acid autoxidation between the E vitamer fraction and the α-tocopherol at 16 and 160 ppm, respectively. E Vitamer fraction was most effective in inhibiting both emulsified cholesterol and linoleic acid. These results suggested that compounds inhibiting cholesterol autoxidation and PUFA autoxidation in both food and biological systems were present in the rice bran extract. Thus, the addition of E vitamer fraction to animal- derived muscle food may be a more compelling way to replace the synthetic antioxidants currently used in the food industry because the former is both natural and effective in inhibiting both cholesterol and PUFA autoxidation.     

The Interaction Between Lipoxygenase‐Catalyzed Oxidation and Autoxidation in Dry‐Cured Bacon and a Model System

A model system was conducted to characterize the interaction between lipid autoxidation and enzyme‐catalyzed oxidation in dry‐cured bacon. This involved the use of a hydroxyl radical (HO?) generating system and the extraction and purification of lipoxygenases (LOX) from pork belly. The results showed that LOX activity rapidly (P < 0.05) increased during the curing of dry‐cured bacon. This may be because of the hydroxyl‐radical‐mediated oxidation from LOX‐Fe²⁺ to LOX‐Fe³⁺, which activates LOX. In addition, experiments of the model system also showed that LOX activity could be inhibited by increasing the substrate concentration, although substrate type and concentration had no effect on autoxidation. Moreover, LOX enzyme‐catalyzed oxidation and autoxidation could act synergistically to promote lipid oxidation irrespective of the substrate (linoleic or arachidonic acid). These results provide useful information for regulating lipid oxidation during the production of dry‐cured pork products.