Oxygen permeation through an oil-encapsulating glassy food matrix studied by ESR line broadening using a nitroxyl spin probe
Oxygen permeation through an oil-encapsulating glassy food matrix studied by ESR line broadening using a nitroxyl spin probe
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DOI：
10.1016/s0308-8146(00)00102-3
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发表时间：
2000-09-01
期刊：
影响因子：
8.8
通讯作者：
Skibsted, LH
中科院分区：
文献类型：
--
作者：
Andersen, AB;Risbo, J;Skibsted, LH
一种非侵入性的方法的基础上扩大的电子自旋共振（ESR）线的存在下的氧气（血氧测定法）已被开发，以确定渗透率的氧气从顶部空间到油，封装在玻璃状基质（食品模型由蔗糖，麦芽糖糊精和明胶通过冷冻干燥）。亲脂性氮氧自由基16-doxylstearic acid，16-DSA，被用作自旋探针，它被发现主要集中在玻璃态基质中的油相中。发现新制玻璃中的氧浓度与大气中的浓度相似，并且冷冻干燥过程显然不能在玻璃状系统固化之前除去氧。在氧气下储存的油封装玻璃增加了基质内的氧浓度，并且发现渗透速率随温度而增加。氧渗透的动力学模型建立，基于获得的速率数据，直到完全饱和的油与氧低于玻璃化转变温度（Tg = 65摄氏度），并在数据的部分氧饱和度以上的玻璃化转变温度。动力学模型包括温度独立的主曲线，并允许结构异质性。氧渗透的活化能被认为是74 +/- 6千焦/摩尔的玻璃基质，和大的值是有利于氧扩散的分子模型，而不是自由体积模型，并符合零级动力学的脂质氧化封装在玻璃基质中，这已经被观察到与氧渗透的速率决定步骤。(C)2000爱思唯尔科技有限公司版权所有。
A non-invasive method based on the broadening of electron spin resonance (ESR) lines in the presence of oxygen (oximetry) has been developed to determine the rate of permeation of oxygen from head space into oil, encapsulated in a glassy matrix (a food model made from sucrose, maltodextrin and gelatine by freeze drying). The lipophilic nitroxide 16-doxylstearic acid, 16-DSA, was used as a spin-probe, and it was found to be concentrated mainly in the oil phase in the glassy matrix. The concentrations of oxygen in the freshly made glasses were found to be similar to the concentration in atmospheric air, and the process of freeze-drying is apparently not able to remove oxygen before the glassy system solidifies. Storing the oil-encapsulating glasses under oxygen increased the oxygen concentration inside the matrices, and the rate of permeation was found to increase with temperature. A kinetic model for the oxygen permeation was established, based on the rate data obtained up to full saturation of the oil with oxygen below the glass transition temperature (T-g = 65 degrees C), and on data for partial oxygen saturation above the glass transition temperature. The kinetic model includes a temperature independent master curve and allows for structural heterogeneity. The energy of activation for oxygen permeation was found to be 74 +/- 6 kJ/mol for the glassy matrix, and the large value is in favour of the molecular model for oxygen diffusion rather than the free volume model, and accords with the zeroth-order kinetics for oxidation of lipids encapsulated in a glassy matrix, which has previously been observed to be associated with oxygen permeation as the rate-determining step. (C) 2000 Elsevier Science Ltd. All rights reserved.