Antioxidant and pro-oxidant activity of green tea extracts in marine oils

The activity of green tea extracts (GTE) on the oxidation of refined, bleached and deodorized (RBD) seal blubber oil (SBO) and menhaden oil (MHO) was examined under Schaal oven conditions at 65 °C. Progression of oxidation was monitored using weight gain, peroxide value (PV) and 2-thiobarbituric acid-reactive substances (TBARS) data. GTE exhibited a pro-oxidant effect in both oils examined, perhaps due to the catalytic effect of their chlorophyll constituents. Therefore, in follow-up experiments, a column chromatographic technique was employed to remove chlorophyll from GTE. The resultant dechlorophyllized green tea extract (DGTE) was applied to both SBO and MHO at 100, 200, 500 and 1000 ppm levels. The antioxidant activity of DGTE was compared with the effects of the commonly-used antioxidants such as butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT) and tert-butylhydroquinone (TBHQ) at 200 ppm and α-tocopherol at 500 ppm. DGTE at ≥200 ppm exhibited excellent antioxidant activity in both oils and its efficacy was higher than that of BHA, BHT and α-tocopherol, but less than that of TBHQ.     

杜仲籽精炼油的氧化稳定性及货架期预测

本文以杜仲籽毛油为原料,经过精炼后以过氧化值、酸价和脂肪酸含量为评判指标,采用Schaal烘箱法探究了5种抗氧化剂在不同浓度和温度下对杜仲籽精炼油氧化稳定性的影响,建立了杜仲籽精炼油货架期模型,预测其货架期。结果表明,添加丁基羟基茴香醚（butyl hydroxyanisole,BHA）、叔丁基对苯二酚（tert-butyl hydroquinone,TBHQ）、维生素E（vitamin E,V_E）、鼠尾草酸（carnosic acid,CA）和L-抗坏血酸棕榈酸酯（L-ascorbyl palmitate,L-AP）的抗氧化效果从大到小依次为TBHQ>CA>L-AP>BHA>V_E,CA、TBHQ、V_E、BHA、L-AP的最佳添加量分别为0.05%、0.02%、0.01%、0.02%、0.02%;随着储藏温度的升高和储藏时间的延长,过氧化值和酸价升高,氧化速度加快,饱和脂肪酸和单不饱和脂肪酸含量增加,不饱和脂肪酸含量减少;杜仲籽精炼油的氧化符合一级氧化动力学反应,通过构建的杜仲籽精炼油货架期模型,预测出在25、40、50和60 ℃的温度下,杜仲籽精炼油的货架期分别为10.70、8.76、7.74和6.89 d,添加抗氧化剂能延缓不饱和脂肪酸的氧化,其中TBHQ的抗氧化效果最好,添加0.02% TBHQ的杜仲籽精炼油的货架期可以延长至41.41、19.71、12.48和8.13 d,说明添加抗氧化剂可以有效延长杜仲籽精炼油的货架期。     

加速氧化测试辣椒茎叶提取物对大豆油氧化稳定性的影响

食用油氧化稳定性是产品的一个重要指标,影响产品的安全性和货架期。采用加速氧化测定法,通过测定过氧化值(PV)、β-茴香胺值(p-AV)、共轭二烯烃(CD)和共轭三烯烃(CT)等指标研究辣椒茎叶提取物(PLSE)对大豆油氧化稳定性的影响。结果显示,在加速氧化测定条件下空白对照组大豆油4个指标逐渐增加,抗氧化剂BHT、BHA、TBHQ和提取物PLSE对大豆油氧化具有不同程度的抑制作用;10、100、200mg/kg剂量组PLSE对大豆油4个氧化指标的抑制作用均小于TBHQ(200 mg/kg),10、100、200 mg/kg剂量组PLSE对大豆油氧化指标PV和p-AV的抑制作用强于BHT(200 mg/kg)和BHA(200 mg/kg);而仅200 mg/kg剂量组PLSE对大豆油氧化指标CD和CT的抑制作用强于BHT和BHA。     

STABILIZATION OF MARINE OILS WITH FLAVONOIDS

Antioxidant activity of a number of flavonoids in refined-bleached and deodorized (RBD) seal blubber oil (SBO) and menhaden oil (MHO) was compared with that of commercially used antioxidants, namely butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT) and tert-butylhydroquinone (TBHQ) as well as α-tocopherol. The study was carried under Schaal oven conditions at 65C and progression of oxidation was followed by monitoring weight gain, peroxide value (PV) and 2-thiobarbituric acid reactive substances (TBARS) value. Among the flavonoids tested in this study, the flavonols, namely myricetin, quercetin and morin exhibited a stronger antioxidant activity than BHA and BHT and effectively stabilized both SBO and MHO. Myricetin was the most effective flavonoid tested in this study and its effect in reducing lipid oxidation was similar to that of TBHQ.     

山茶油的氧化稳定性及其调节血脂作用的研究

采用Schaal烘箱法,以过氧化值(POV)为评价指标,考察了温度、光照、抗氧化剂对山茶油氧化稳定性的影响;通过建立高脂模型,研究了山茶油对大鼠血清中总胆固醇(TC)、三酰甘油(TG)、低密度脂蛋白胆固醇(LDLC)、高密度脂蛋白胆固醇(HDL-C)水平的影响。结果表明:常温下山茶油具有良好的储藏稳定性,但随着储藏温度升高,山茶油的氧化速度明显加快;自然光和日光灯照射对山茶油氧化反应均有明显的促进作用;抗氧化剂BHT、BHA、TBHQ和PG对山茶油的氧化反应均有一定的抑制作用,其中TBHQ和PG效果比较明显;相比高脂模型组,山茶油有显著降低血清TG和TC的作用,并随剂量上升效果增强,而且相同剂量下,山茶油对TG的降低作用强于TC,对HDL-C、LDL-C具有一定的影响但是效果不显著。     

Gas Chromatographic Determination of Butylated Hydroxyanisole, Butylated Hydroxytoluene and Tertiarybutyl Hydroquinone in Soybean Oil

Oils containing different levels of the most common phenolic antioxidants, butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), and tertiarybutyl hydroquinone (TBHQ) from 0–200 ppm were analyzed by a new gas chromatographic method. The antioxidants in oils were isolated by nitrogen gas purging, collected on Tenax GC coated with polymetaphenoxylene, and then separated and quantitated by gas chromatography. This method requires neither extraction of antioxidants from oil nor derivatization of antioxidants. The correlation coefficients (r) between gas chromatographic peak heights or peak area and their concentrations in oils were 0.99 for BHA, BHT, and TBHQ. This simple gas chromatographic method can determine as little as 10 ppm pf BHA, BHT, or TBHQ in oils in an hour.     

Direct Spectroscopic Observation of Singlet Oxygen Quenching and Kinetic Studies of Physical and Chemical Singlet Oxygen Quenching Rate Constants of Synthetic Antioxidants (BHA,BHT, and TBHQ) in Methanol

Abstract: Singlet oxygen quenching by synthetic antioxidants (BHA, BHT, and TBHQ) was directly observed by spectroscopic monitoring of luminescence at 1268 nm. The luminescence data showed unambiguous evidence of singlet oxygen quenching by synthetic phenolic antioxidants with the highest activity for TBHQ, followed by BHA and BHT. The protective activities of these synthetic antioxidants on α-terpinene oxidation with chemically-induced singlet oxygen under dark further confirmed their singlet oxygen quenching abilities. Total singlet oxygen quenching rate constants (k_r + k_q) of BHA, BHT, and TBHQ were determined in a system containing α-terpinene (as a singlet oxygen trap) and methylene blue (as a sensitizer) during light irradiation, and the values were 5.14 × 10⁷, 3.41 × 10⁶, and 1.99 × 10⁸ M⁻¹s⁻¹, respectively. After the k_r value of α-terpinene was first determined, the k_r values of the synthetic antioxidants were calculated by measuring their relative reaction rates with singlet oxygen to that of α-terpinene under the identical conditions. The k_r values of the BHA, BHT, and TBHQ were 3.90 × 10⁵, 1.23 × 10⁵, and 2.93 × 10⁶, M⁻¹s⁻¹. The percent partition of chemical quenching over total singlet oxygen quenching (k_r × 100)/(k_r + k_q) for BHA, BHT, and TBHQ were 0.76%, 3.61%, and 1.47%, respectively. The results showed that the synthetic antioxidants quench singlet oxygen almost exclusively through the mechanism of physical quenching. This represents the first report on the singlet oxygen quenching mechanism of these synthetic antioxidants. Practical Application: The synthetic antioxidants, especially TBHQ, have been found to have a strong singlet oxygen quenching ability. This article also clearly showed that singlet oxygen quenching by synthetic antioxidants was mainly by the physical quenching mechanism. The results suggested that these synthetic antioxidants, especially TBHQ, could be used practically for the protection of the food components such as edible oils and vitamins against singlet oxygen induced oxidations without significant losses of antioxidant activity during storage under light.     

Antioxidants in Restructured Beef/Pork Steaks

The effects of added antioxidants on restructured combination (50:50) beef-pork steaks were studied. Steaks were formulated to contain 20% fat and 0.75% salt. Antioxidants used at a 0.02% level (based on fat content of meat) were butylated hydroxyanisole (BHA), tertiary butyl hydroquinone (TBHQ), and a combination of BHA and TBHQ. Cooked steaks were evaluated for sensory properties and overall acceptability, initially and after 4, 8, 12, 16, an 20 wk of freezer storage. Steaks were also evaluated after the various storage times for 2-thiobarbituric acid (TBA) values, subjective color by panel evaluation, objective color with the Hunter color difference meter, tensile strength, shear value and cooking loss. Flavor and overall acceptability were significantly better in treated samples as compared to control samples. BHA was more effective in protecting color and TBHQ was more effective in protecting flavor (P<0.05). All treated samples showed lower TBA values than control samples (P<0.05).     

Rapid micropreparation procedure for the gas chromatographic-mass spectrometric determination of BHT, BHA and TBHQ in edible oils

A rapid, accurate and organic solvent saving procedure has been developed for the GC/MS determination of three phenolic antioxidants butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA) and butyl hydroquinone (TBHQ) in vegetable oils. The method involves two-step microextraction and a centrifugal procedure in a 2 mL autosampler vial, consuming only 50 mg sample and total 1 mL acetonitrile. Recoveries of the phenolic antioxidants when spiked to soya bean oil, peanut oil and cereal cooking oil at 50, 200 and 250 mg/kg, respectively were in the ranges 95.6-104.3% for BHT, 99.7-107.5% for BHA and 93.6-103.8% for TBHQ with the relative standard deviation (RSD) were less than 3% for their independent measurements. The developed method was repeatable and could be applied to determine trace amounts of phenolic antioxidants in vegetable oils.     

THE EFFECTS OF TBHQ AND α-TOCOPHEROL ON QUALITY CHARACTERISTICS OF REFINED-BLEACHED AND DEODORIZED PALM OLEIN (RBDPO) DURING DEEP-FAT FRYING

The changes in quality characteristics of refined, bleached and deodorized palm olein (RBDPO) during deep-fat frying for 5h/day for 5 consecutive days in four systems were compared. The four systems were RBDPO without antioxidant (system 1); RBDPO with 200 ppm TBHQ (system 2); RBDPO with 100 ppm TBHQ + 100 ppm α-tocopherol (system 3); and RBDPO with 200 ppm a-tocopherol (system 4). The addition of the antioxidants reduced peroxide value, anisidine value, free fatty acids, polar components, polymer content, the rate of the changes in iodine value and the rate of oxidation of C18:2. Adding antioxidants, however, caused darkening of the oil and increased the formation of foam during deep-fat frying.     

Control of Lipid Oxidation in Cooked Ground Pork with Antioxidants and Dinitrosyl Ferrohemochrome

A number of antioxidants were added to ground meat prior to cooking to achieve oxidative stability. The 2-thiobarbituric acid (TBA) numbers of cooked-meat samples after storage for up to 35 days were determined. Of the antioxidants tested, butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), propyl gallate (PG), t-butylhydro-quinone (TBHQ), trihydroxybutyrophenone (THBP), nordihydro-guaiaretic acid (NDGA), catechol, and ethoxyquin were effective at a level of 200 ppm giving TBA values of less than one. BHA, TBHQ, and ethoxyquin were equally effective at a level of 30 ppm. Ascorbyl acetal and ascorbyl palmitate retarded lipid oxidation effectively (TBA values of slightly over one after five weeks of storage). The cooked cured-meat pigment showed some antioxidant effect which increased with increasing concentration, and at 18–24 ppm was better than that of 200 ppm of α-tocopherol.     

电分析法同时快速测定植物油中TBHQ、BHA和BHT的研究

研究抗氧化剂TBHQ、BHA和BHT在玻碳电极上的伏安性质,三者的循环伏安图表明:3个峰形良好的氧化峰分别对应:TBHQ的氧化峰电位为590 mV,BHA的氧化峰电位为710 mV,BHT的氧化峰电位为1 050 mV,只有一个还原峰,电位为-90 mV。通过实验优化了电分析法测定植物油样抗氧化剂的分析技术参数。借助最小偏二乘法(PLS),利用电化学分析法预测了人工模拟试样中的3种抗氧化剂的含量,预测结果及加标回收率结果较好。利用所开发的方法测定了实际油样中的抗氧化剂的含量,其回收率在94%~104.1%,结果表明该法同时测定植物油中2种及以上的抗氧化剂是可行的,而且无需提取、分离及清洗等预处理程序,应用潜力巨大。     

Oxidative stability of palm‐ and soybean‐based medium‐ and long‐chain triacylglycerol (MLCT) oil blends

BACKGROUND: Medium‐ and long‐chain triacylglyerols (MLCT) enzymatically esterified using Lipozyme RM IM lipase has very low oxidative stability as it does not contain any antioxidants. The aim of this work was to study the ability of various antioxidants to increase the oxidative stability of palm‐ and soybean‐based MLCT blends which assist to bring up the oxidative stability of both MLCT blends. In this study, the effectiveness of rosemary extracts, sage extracts, tert‐butylhydroquinone (TBHQ) and mixtures of tert‐butyl‐4‐hydroxyanisole (BHA) and tert‐butyl‐p‐hydroxytoluene (BHT) in protecting against oxidation of various MLCT blends was investigated. RESULTS: Blending of MLCT oil with either palm olein or soybean oil improved its smoke point values and oxidative stability. TBHQ addition to both palm‐ and soybean‐based MLCT blends increased oxidative stability. Combination of BHA and BHT showed no significant improvement (P > 0.05) in ability to protect blends from oxidation compared to natural antioxidants such as sage or rosemary extracts. CONCLUSION: Blended oils with 500 g kg^?1 MLCT and 500 g kg^?1 palm olein (MP5) were the most suitable for use at high temperature based on the fatty acid composition of the MLCT blends, which subsequently had an effect on thermal oxidative stability. In general, addition of either natural or synthetic antioxidant assisted in improving the antioxidative strength of both MLCT blends. MLCT blends with added TBHQ showed the highest thermal oxidative stability among the antioxidants used. Copyright © 2008 Society of Chemical Industry     

Use of antioxidants for enhancing oxidative stability of bulk edible oils: a review

Edible oils industry is using synthetic and natural antioxidants to enhance the oxidative stability of bulk edible oils. Due to safety concerns of BHA, BHT and TBHQ, there is an ongoing effort to find an effective and safe replacement. Finding a safe antioxidant or its synergistic mixture, which delays, retard or prevent the oxidation of bulk oil without changing the colour or flavour upon addition is a challenge. In this review, a brief account of chemical basis of oxidative deterioration of the stored oil is given. The effectiveness of most widely experimented antioxidants such as tocopherols, carotenoids, ascorbic acid and its derivatives, lignan compounds, flavonoids, polyphenols and phenolic acids in various edible oils have been reviewed. Further, the synergistic and antagonistic combination of these antioxidants in controlling oxidative degradation of edible oils has been discussed.     

Interaction of packaging materials and vegetable oils: oil stability

The effects of different plastic films (polyethyleneterephthalate, polyvinylchloride, polypropylene and polystyrene) on the stability of olive, sunflower and palm oils were studied at 24 and 37°C during 60 days of storage. The changes in peroxide value (PV) and thiobarbituric acid value (TBA) were significantly higher (p≤0.05) in the plastic bottles than in glass. Our study indicates that the plastic permeability has played a major role in oil stability. However, both butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) were found to leach out from plastics films into vegetable oils during storage. The rate of oxidation was not reduced by antioxidant migration from plastic films to oils. Natural antioxidant (vitamin E) retarded the oxidation rate, and this was dependent on its concentration in oils examined. The results showed that the ranking of stability of oil samples is PVC≥PET>PP≥PS. Further, the stability was dependent on the type of oil. Palm oil exibited high stability properties while the highest oxidation rate was observed in sunflower oil. In addition, increasing storage temperature accelerated the oxidation and limited the stability of vegetable oils.     

Oxidative stability of oil from blubber of harp seal (Phoca groenlandica) as assessed by NMR and standard procedures

Oils from seal blubber and cod liver were extracted, refined and bleached in a laboratory scale process. Oxidative stability of oils was evaluated over a 16-day period under accelerated oxidation conditions at 65°C. Peroxide value (PV), contents of conjugated dienes (CD) and trienes (CT), 2-thiobarbituric acid reactive substances (TBARS) and p-anisidine values (AnV) were determined. In addition, NMR spectroscopy was used to monitor relative changes in the proton pattern of the fatty acids of oils during storage. Cod liver oil showed higher PV, CD, CT and TBARS values as compared with seal blubber oil. The ratio of aliphatic to olefinic protons in both oils determined by NMR spectroscopy increased steadily over the entire length of the storage period, indicating progressive oxidation of unsaturated fatty acids in both oils. A significant correlation (P ≤0·05) was found between these ratios and TOTOX values (2PV + AnV) for both oils, thus suggesting that NMR methodology can be used as an effective means to simultaneously estimate both primary and secondary oxidation changes.     

紫外光下4种抗氧化剂在猪油中的抗氧化效果

旨在研究光照对油脂抗氧化剂抗氧化效果的影响。分别研究在254、365 nm波长光照射下,猪油中添加丁基羟基茴香醚(BHA)、2,6-二叔丁基-4-甲基苯酚(BHT)、特丁基对苯二酚(TBHQ)、没食子酸丙酯(PG)对其过氧化值、酸价、丙二醛值、共轭二烯类值、共轭三烯类值的影响。结果表明,与空白相比,在254 nm光照下,4种抗氧化剂抑制猪油过氧化值、酸价、丙二醛值、共轭二烯类值、共轭三烯类值的效果差异不显著(p>0.05);在365 nm光照下,BHA、BHT、PG抑制猪油过氧化值、酸价、共轭二烯类值、共轭三烯类值效果差异性不显著(p>0.05),抑制丙二醛效果差异极显著(p<0.01)。TBHQ抑制猪油酸价、共轭三烯类值效果差异不显著(p>0.05),抑制过氧化值、共轭二烯类值差异显著(p<0.05),抑制丙二醛效果差异性极显著(p<0.01)。由此说明,在254、365 nm光照射下,BHA、BHT、PG基本没有抗氧化效果,TBHQ的效果也不够理想。     

Effects of storage conditions on oxidative stability of soybean oil

Soybean oil in the presence or absence of 200 µg g^?1 tert‐butyl hydroquinone (TBHQ) was subjected to accelerated oxidative storage at 60 °C for 10 days or stored at room temperature for 12 months. Tocopherol contents of the oil decreased, whereas the headspace volatiles and peroxide values (PV) increased as the storage time increased. During accelerated storage, TBHQ was effective in retarding the formation of hydroperoxides and headspace volatiles in the oil. TBHQ also protected tocopherols, especially α‐tocopherol, from oxidation. During long‐term room‐temperature (LTRT) storage, the changes in PV between the oils with and without TBHQ were similar, but the oil with TBHQ had lower headspace volatile contents than that without TBHQ. Headspace volatile analysis was more suitable than PV measurement for predicting the oxidative stability of soybean oil during LTRT storage. The contents of hexanal or (E)‐2‐heptenal in the oil at 1–5 days of accelerated storage could be used to predict those of the corresponding compound in the oil at 0–4 weeks of LTRT storage. Copyright © 2005 Society of Chemical Industry     

MLM型结构脂质特性及氧化稳定性研究

比较研究了菜籽油、菜籽油为底物酶改性制备的含辛酸MLM(中碳链-长碳链-中碳链)型结构脂质的质量指标及其氧化稳定性.含38.1％辛酸的MLM型结构脂质中辛酸96.3％位于甘油sn-1,3位,其游离脂肪酸、皂化值高于菜籽油,氧化稳定性指数(OSI值)、过氧化值(PV)低于原料油脂.添加6种不同抗氧化剂后,结构脂质OSI值有不同幅度的改进,以叔丁基对苯二酚(TBHQ)效果最为显著.添加200 mg/kgTBHQ后MLM型结构脂质的OSI值由5.05 h上升到20.1 h,PV、共轭二烯与硫代巴比妥酸随氧化时间延长而增幅减小.     

二氢杨梅素对4种植物油脂抗氧化作用研究

研究二氢杨梅素(DMY)对植物油脂抗氧化作用。采用紫外可见分光光度计和烘箱强化贮藏法,考察DMY对DPPH自由基清除能力和对山茶油、亚麻籽油、紫苏籽油和油酸的抗氧化作用。结果表明:DMY对DPPH自由基清除能力明显高于TBHQ、BHT、BHA和TP;当抗氧化剂添加量为0.05%时,不同抗氧化剂在山茶油和油酸中抗氧化作用强弱顺序为TBHQDMYBHABHTTP;不同抗氧化剂在紫苏籽油和亚麻籽油中抗氧化作用强弱顺序为TBHQBHABHTDMYTP;DMY还能协助增强其他抗氧化剂的作用;DMY对4种植物油脂抗氧化效果强弱顺序为山茶油油酸亚麻籽油紫苏籽油。