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     

Correlation between plasma antioxidant capacity and verbascoside levels in rats after oral administration of lemon verbena extract

Phenylpropanoids are the main class of compounds from lemon verbena which have shown a wide biological activity, verbascoside being the most abundant one. In this work, the composition of a lemon verbena extract was elucidated by HPLC-ESI-MS/MS and one flavone and one methoxylated phenylpropanoid were found in this source for the first time. The antioxidant activity of the lemon verbena extract was fully characterised by several methodologies. Unexpectedly, the extract was especially active in lipophilic environments and lipid peroxidation inhibition assay, as it was found for pure verbascoside. The lemon verbena extract, containing verbascoside as its major bioactive compound, was acutely administered to rats and verbascoside was the only metabolite detected in plasma samples as measured by HPLC mass spectrometry. The correlation between the highest verbascoside concentration in plasma and maximum plasma antioxidant capacity was observed at 20 min as measured by different techniques, i.e. minimum malondialdehyde (MDA) generation, highest ferric-reducing ability of plasma (FRAP value) and maximum superoxide dismutase activity (SOD). Therefore, the in vitro measurements of the antioxidant activity of lemon verbena extract may significantly support the antioxidant activity observed in vivo in this work. Moreover, neither evidence of acute oral toxicity nor adverse effects were observed in mice when the lemon verbena extract containing 25% verbascoside was used at a dosage of 2000 mg/kg.     

二丁基羟基甲苯对调理鸡肝贮藏过程中抗氧化效果的影响

研究调理肉制品在贮藏过程中的脂肪氧化情况以及不同添加水平的二丁基羟基甲苯(BHT)的抗氧化效果。以调理鸡肝为试材,BHT 添加量分别为0.05、0.10、0.15、0.20g/kg 处理鸡肝,然后在冻藏条件下贮藏,通过测定其在不同贮藏时期的酸价、过氧化值和硫代巴比妥酸值判定其脂肪氧化的程度及BHT 的抗氧化效果。结果表明：除BHT 添加量0.20g/kg 组外,其他各组脂肪氧化主要开始于贮藏第15 天,之后脂肪氧化产物发生不同程度的分解;4 个处理组中,BHT 添加量0.20g/kg 可有效抑制过氧化值增长,BHT 添加量0.15g/kg 可有效减少脂肪氧化产物的分解。BHT 在调理鸡肝贮藏过程中有较好的抗氧化效果。     

Latex coatings containing antifeedants: Formulation,characterization, and application for protection of conifer seedlings against pine weevil feeding

Latex-based coatings for protection of tree seedlings against pest insect feeding are evaluated with respect to surface-, mechanical-, and release properties and antifeedant activity. The latex dispersion Eudragit copolymer (EC) was used to form the coatings, 2,6-di-tert-butyl-4-methylphenol (BHT) and cis-dihydropinidine (Alk) as antifeedants, and a thickener and a alkylglucoside based nonionic surfactant were used as additives to optimize the release- and mechanical properties of coatings. Coating characterization was performed with respect to surface morphology (atomic force microscopy, AFM) and surface wetting (contact angle), as well as to mechanical (tensile stress- and tensile strain at break) properties. Surface smoothness and wettability as well as elasticity increased with addition of the surfactant. The optimized coatings were found to be elastic and water resistant at 3–6 wt.% of BHT and 3 wt.% of surfactant. BHT was released into SDS/water at very low rates. Several formulations of BHT and Alk were efficient in preventing the feeding on conifer bark by a pine insect, Hylobius abietis both in laboratory (no-choice) and in field (3 months) tests.     

Isolation of powerful antioxidants from the medicinal halophyte Limoniastrum guyonianum

The antioxidant capacities of the crude extract, aqueous and ethyl acetate partitions of Limoniastrum guyonianum Boiss. (Zita) were investigated in this study. The ethyl acetate phase exhibited a significant antioxidant activity as judged by total antioxidant activity, DPPH test and reducing power. Fractionation of this extract by centrifugal partition chromatography (CPC) using quaternary Arizona solvent systems composed of n-heptane/ethyl acetate/methanol/water led to ten fractions. The antioxidant capacities of these fractions were assessed using the same previous tests. Fraction 8 showed the highest antioxidant capacity (1291.1mg GAE/g DR), the power ability to quench DPPH radical (IC(50)=2μg/ml) and to reduce Fe(3+) (EC(50)=65μg/ml). From this fraction, three powerful flavonoids were isolated (1-3): gallocatechin (1), epigallocatechin (2) and epigallocatechin-3-O-gallate (3). These findings suggest that the antioxidative property of L. guynianum is may be related to the presence of these flavonoids, which can be used in various industrial fields.     

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.     

Study of Bake Hardenability and Strengthening Mechanism of Hot Rolled Low Carbon Steel

The controlled rolling and controlled cooling,bake hardening experiments have been carried out for the test steel,mechanical property test of the sample and microstructure analysis have been made by tensile testing machine,optical microscope,TEM and X-ray diffractometer.The results show that fine and uniform microstructures can achieve much higher BH and BHT values;With the increase of pre-strain there is a trend of increase first and then decrease in the BH and BHT values;bake hardening mechanism mainly consists of Cottrell atmosphere strengthening,second phase strengthening,dislocation strengthening.     

Effectiveness of synthetic and potential natural antioxidants in improving the stability of sheep's anhydrous butter fat during long-term storage

Sheep's anhydrous butter fat as prepared by including separately heat grits, turmeric, rosemary, sage, rue and fennel at a level of 75 g dry matter kg^?1 butter. The product as stored at room temperature in clear glass jars for a period of one year. The storage stabilities of the anhydrous butter fat samples ere compared ith a control and ith a sample treated ith a 1:1 mixture of BHA and BHT at a level of 0.25 g kg^?1. Both storage time and type of treatment had highly significant effects (P?0.01) on the peroxide value and free fatty acid content of the product. None of the treatments succeeded in keeping the peroxide value belo 5 mEq O₂ kg^?1 beyond the fourth month of storage. The BHA-BHT mixture and rosemary helped extend the peroxide induction period to 10 and 6 months respectively. Turmeric and heat grits ere as effective as BHA-BHT in controlling the oxidative rancidity during the first four months of storage. The rest of the herbs exhibited a pro-oxidant effect throughout the study hen they ere used separately. In a second experiment, some cases of positive synergistic interactions ere observed beteen turmeric and heat grits on one hand and the herbs used in the study on the other. This pattern as not regular as negative interactions ere also observed in some other cases. Free fatty acid content of all the samples remained belo 10 g kg^?1 as oleic acid; hoever, fennel had a significant (P?0.05) effect on controlling the evolution of free fatty acids.     

凝胶渗透色谱-气相色谱法测定食用油脂中抗氧化剂BHA、BHT

研究了采用凝胶渗透色谱对食用油脂样品进行脱油脂前处理,气相色谱仪(FID检测器)对食用油脂中抗氧化剂BHA、BHT进行定量分析的方法。该方法在实际样品检测中的加标回收率均在89.4%～96.4%之间,相对偏差均小于4.32%,最低检测限为0.002mg/mL。与国家标准方法相比,该方法使样品前处理步骤得到简化,操作方便,提高了测定的准确性与灵敏度,适用于油脂及富含油脂食品中BHA、BHT的检测。     

用分子包埋法对BHT进行微胶囊化研究及应用

本文研究以β-环糊精为壁材,采用超声波法对抗氧化剂BHT进行微胶囊化。以产品的包埋率、产率为评定指标,选取最佳心材与壁材的配比,最佳处理时间。结果表明:心材与壁材的最佳比例为12:88,最适超声波时间为45min。