电子自旋共振波谱法评价花生油氧化稳定性的可行性研究

为探究花生油加速氧化过程中的自由基链式反应,利用电子自旋共振波谱法（ESR）研究花生油的加速氧化过程,结果发现加速氧化过程中产生大量的烷基自由基（R·）以及少量的烷氧基（RO·）和过氧化自由基（ROO·）。对ESR法与Rancimat法（经典油脂氧化稳定性测定方法）进行比较研究,分别利用这两种方法测定添加不同抗氧化剂花生油的氧化稳定性,发现ESR法的滞后时间（Lagtime）和Rancimat法的诱导时间（IP）结果一致,即加入0.02%TBHQ和0.01%柠檬酸（CA）的花生油中自由基生成量最少,滞后时间最长,且诱导时间最长。此外,滞后时间与诱导时间之间具有良好的线性关系,回归方程为[Lagtime]=79.724[IP]-165.630（R2=0.9688）。综上所述,ESR法可预测Rancimat法的结果,也可作为一种评价花生油氧化稳定性的方法。      

电子自旋共振技术分析植物油氧化

采用电子自旋共振（ESR）从微观角度分析了棕榈油、菜籽油、葵花籽油、亚麻籽油4种植物油在120、150、180 ℃加热氧化时的自由基变化,并对自由基信号强度与过氧化值的相关性进行了研究。结果表明：同一温度下加热0～36 h,自由基信号强度随着加热时间的延长而增加,表明氧化程度与自由基加合物的量成正相关;同时,自由基信号强度与过氧化值的相关性较强（P<0.05）。ESR方法可表征植物油的热氧化程度。     

电子自旋共振法与可见分光光度法对比测定葛根黄酮抗氧化性

采用电子自旋共振法(ESR)对葛根黄酮4个提取样(CEP1,CEP2,CEP3,CEP4)抗氧化性能进行研究,同时采用可见分光光度法进行对比实验。将4份样品与1,1-二苯基-2-三硝基苯肼(DPPH)溶液混合,分别置于电子顺磁共振波谱仪与可见分光光度计中检测。结果表明:在ESR测定法里,不同的反应时间,同一份样品对DPPH·的清除率和质量浓度成正比例关系,在质量浓度为60 mg/L时,自由基的清除率有显著的提高。ESR处理时间30 min,60%乙醇洗脱液葛根冻干粉自由基清除率可以达到100%。ESR法能更灵敏、更准确地测定自由基清除效果。     

利用电子自旋共振技术研究黄海海燕体壁多糖的体外抗氧化活性

以新鲜黄海海燕体壁为原料,制备粗多糖及精多糖。采用电子自旋共振波谱技术(ESR),检测不同浓度的黄海海燕体壁粗多糖及精多糖对羟基自由基、DPPH和超氧阴离子的清除能力。结果表明:黄海海燕体壁粗多糖及精多糖对羟基自由基、DPPH和超氧阴离子的清除能力随浓度升高而增强,黄海海燕体壁粗多糖对3种自由基清除能力的IC50值分别为59.56,27.29,32.36mg/mL;精多糖对3种自由基清除能力的IC50值分别为44.96,13.97,30.51mg/mL。在相同多糖干粉浓度下,黄海海燕体壁精多糖对羟基自由基、DPPH和超氧阴离子的清除能力强于黄海海燕体壁粗多糖。     

电子自旋共振技术及其在食品脂质氧化检测中的应用进展

电子自旋共振(electron spin resonance,ESR)技术是以含未成对电子的物质如自由基、过渡金属离子、三重态分子等为检测对象的光谱分析技术。因其能通过检测未成对电子而分析有机导体、金属化合物、化学物质的光合作用,故其广泛应用于物理、化学、医学、生物等研究领域。又因ESR技术可对食品成分发生物理、化学变化产生的自由基进行定性和定量分析,故其在食品检测领域也具有广泛的应用。本文首先介绍了食品中的脂质氧化、ESR技术的原理、自旋捕获法及捕获剂的选择依据,明确了脂质氧化早期可产生自由基与基于自旋捕获法的ESR技术可定性、定量自由基之间的关系。在此基础上,重点综述了畜禽肉制品、水产品、植物油脂等富脂食品在加工、贮藏过程中,ESR技术检测其脂质是否发生氧化反应及氧化反应程度的研究进展。为ESR技术在食品脂质氧化检测中的广泛应用提供理论依据。     

提升电子自旋共振波谱仪灵敏度的途径

磁共振主要是磁矩不等于零的原子或者是原子核通过稳恒磁场的作用而对电磁辐射产生共振吸收的一种现象。目前,核磁共振仪器已经在诸多领域得到广泛应用,而共振波谱仪也越来越成为人类进步必不可少的仪器设备,在科学、环境、经济、社会问题等方面都占据着重要的地位。     

辐照食品检测鉴定方法

本文介绍了辐照食品常用的检测方法,对其原理、适用范围和局限性进行了综述,为辐照食品的研究和检验提供参考。     

辐照对食品营养成分的影响

介绍了辐照对食品中水分、蛋白质、糖类、维生素和脂肪的影响。研究表明辐照对食品中各种营养成分的影响很小，辐照食品是卫生安全的。     

利用电子自旋共振技术评估啤酒的抗氧化剂

利用电子自旋共振技术评估抗氧化剂异Vc钠、焦亚硫酸钠和还原酚对啤酒中自由基的影响。还原酚和异Vc钠虽能在短期内能有效抑制自由基的产生,但不利于啤酒的长期保质。焦亚硫酸钠的添加对自由基的产生起单向抑制作用,且添加量与Lag Time有较好的线性相关。在对市售商品啤酒进行测定时,啤酒中所含的二氧化硫对啤酒的Lag Time值和新鲜度均有正向作用。     

A method of testing for irradiation of poultry

A method for the detection of irradiated poultry is described. For chicken, free radicals produced by ionizing radiation within the hard crystalline matrix of bone can be detected by the technique of electron spin resonance (ESR) spectroscopy. The ESR signal increases linearly with dose over the likely commercial range and is stable over the probable shelf-life under likely storage conditions. The lower limit of detection is equivalent to a radiation dose of 50 Gy. The test appears equally applicable to turkey, duck and goose.     

Factors influencing the yield of free radicals in irradiated chicken bones

The exposure of foodstuffs containing bone or other calcified tissue to a dose of ionizing radiation results in the formation of long lived free radicals which give rise to characteristic ESR signals. The presence of this signal provides clear evidence that the sample has been irradiated. In order to determine the radiation dose by post-irradiation calibration, it is necessary to consider factors that might influence the radical yield and to allow for the stability of the radicals under likely conditions of storage. Using chicken bone we have shown that the yield is influenced by the nature of the bone, temperature of irradiation, and gaseous atmosphere, although not by dose rate, water content, or type of radiation. Cooking before irradiation greatly enhances the subsequent yield of radicals, while cooking after irradiation causes little or no destruction of the radiation-induced radicals, which also appear to be unaffected by length and conditions of storage.     

An Electron Spin Resonance Study of Evolution of Organic Free Radicals in Irradiated Pepper During Heat Treatment

ABSTRACT: The thermal evolution behavior of the organic free radicals induced in irradiated black pepper was studied by electron spin resonance spectroscopy. To analyze the time-dependent evolution process, we used the theory of transient phenomena, that is, an ordinal differential equation, as well as the nonlinear least squares numerical method. We found that the radical evolution that occurred in the irradiated pepper obeys a single exponential function and yields a unique time constant. The evolution of the organic free radical undergoes a simple reaction process of a single radical species.     

Accuracy of the Calibration Curve Method for Absorbed Dose Assessment in Irradiated Refrigerated Chicken Bone

ABSTRACT: The influence of the decay of the radiation induced free radicals on electron spin resonance (ESR) bone dosimetry was studied. The absorbed doses in irradiated bone are usually assessed by applying correction factors for decay. An alternative procedure is presented in which the ESR readout was performed only when the ESR signal had reached good stability for the bone samples used to establish the calibration curves and also on bones for which absorbed dose assessment was to be made. The results of the evaluated doses obtained by using this approach were the same as the ones obtained by using corrections for the decay of ESR signals.     

Identification of Irradiated Norway Lobster (Nephrops norvegicus) Using Electron Spin Resonance (ESR) Spectroscopy and Estimation of Applied Dose Using Re-irradiation: Results of an In-House Blind Trial

An in-house blind trial on Norway lobster (Nephrops norvegicus) was carried out in which 72 coded samples were correctly identified. The samples were either left unirradiated or had been given doses of 1·03, 2·39 or 3·40 kGy and stored for 0, 7 or 14 days at 1°C. Using re-irradiation, the doses received by the samples identified as irradiated were determined with either linear, quadratic or asymptotic equations being fitted to the data. The most successful estimates of absorbed dose were obtained using a quadratic fit, with average values of 1·71, 2·98 and 3·45 kGy being calculated. © 1997 SCI.     

茶叶辐照的热释光分析研究

不采用二次辐照,将TL 分析法应用于辐照茶叶的定性鉴定。分离并收集茶叶中黏附的硅酸盐,采用热释光剂量仪测量获得硅酸盐的热释光发光曲线,比较未辐照与辐照不同剂量茶叶的热释光发光曲线的积分强度、峰值和峰值温度等特征参数。未辐照茶叶的热释光发光曲线的积分强度小于50、峰值小于0.4、峰值温度大于260℃;反之,辐照茶叶的热释光发光曲线的积分强度大于50000、峰值大于600、峰值温度位于160～190℃。TL 分析法能判别出茶叶的辐照与否,尤其对不能满足参比剂量辐照条件的样品很有帮助。     

用ESR检测二氢杨梅素对自由基的清除作用的研究

为研究二氢杨梅素对不同活性氧自由基的清除作用,采用ESR和自旋捕集技术测定二氢杨梅素对·OH、·O2-和DPPH自由基的清除效果。结果表明,二氢杨梅素对活性氧自由基有较好的清除作用,并呈现出一定的量效关系;二氢杨梅素对活性氧自由基有较好的清除作用,并呈现出一定的量效关系;二氢杨梅素清除和抑制·O2-、·OH-和DPPH自由基的IC50分别为7.4μg/mL、297.8μg/mL和12.4μg/mL,表明二氢杨梅素对不同自由基的清除能力有显著差异,对超氧自由基具有更强的清除作用。     

基于超微弱发光技术检测辐照食品的研究

基于超微弱发光检测技术,研究即食食品(麦片,藕粉)经0～12kGy剂量辐照后光子信号的变化,并探讨超微弱发光用于鉴定即食辐照食品的判定方法。试验结果表明:两种即食食品辐照前后的超微弱光子计数有明显的区别,光子计数与辐照剂量呈正相关,检测阈值可低至0.3kGy。当添加检测液后的最大光子数为本底的15倍以上时,可判定为该样品经过辐照处理。     

Singlet Oxygen Detection in Skim Milk by Electron Spin Resonance Spectroscopy

ABSTRACT: 2,2,6,6-Tetramethyl-4-piperidone (TMPD) can react with singlet oxygen to produce the corresponding nitroxide, 2,2,6,6-tetramethyl-4-piperidone-1-oxyl (TAN), which can be detected by electron spin resonance (ESR) spectroscopy. ESR detected the formation of TAN in 5 μM riboflavin phosphate buffer, or skim milk containing 20 mM TMPD during illumination. The effects of illumination, riboflavin, and oxygen on the formation of TAN indicated that the presence of each was required for singlet oxygen formation. The photo reduced riboflavin might reduce TAN to the hydroxylamine of TAN, thus decreasing the paramagnetic TAN signal. Maximum concentration of TAN was obtained at an added 10 mM riboflavin in buffer solution or in skim milk after 15 min of illumination in the presence of oxygen.