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Molecular Mobilty and Food Preservation with Relevance to Glass Transition

与玻璃化转变相关的分子迁移率和食品保存

基本信息

批准号：
17580117
负责人：
KUMAGAI Hitoshi
金额：
$ 2.43万
依托单位：
Kyoritsu Women's University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2005
资助国家：
日本
起止时间：
2005 至 2007
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-17580117/
关键词：
glass transition water plasticizer pulse-NMR micro-Brownian motion water sorption isotherm caking color chanae 水分収着等温線水分収着速度溶液熱力学固結 DSC

项目摘要

The glass transition has attracted great interest from food scientists in recent years, because many phenomena related to food manufacturing and preservation could be systematically explained with a concept of glass transition : for example, food materials maintain their physical and chemical stability better in a glassy state than in a rubbery state. The glass transition temperature T_g for many foods has been determined by thermal analysis such as differential scanning calorimetry (DSC). The thermal analysis, however, does not provide information on molecular mobility. In this study, the difference in molecular mobility between glassy and rubbery materials was analyzed by a pulse NMR that can detect the mobility of the components in the system by analyzing the relaxation behavior of the protons, the and the effect of water on the molecular mobility being examined. In addition, the influence of glass transition on two important quality change of food powders, caking and color change w … More as investigated.The glass transition temperature T_g for foods was determined by DSC. The values of T, for the foods examined decreased with increasing moisture content, due to plasticizing effect of water. As for wheat gluten, the critical point of color change AE can be taken as to correspond to the glass to rubber transition point. The DSC data of for gluten also support that gluten is in glassy state above the critical point of color change.Water sorption isotherms of foods examined were sigmoidal similar to many food materials ; the amount of sorbed water increased drastically above glass to rubber transition point. The water sorption rate takes a maximum value near water activity 0.5-0.6.FID (Free Induction Decay) of NMR was satisfactory described by a combination of two or three components, Gaussian, exponential, and Gaussian lineshapes. M_2 showed one or two transition temperatures. At low moisture content, the percentage immobile component was dominant, but it decreased as moisture content increased. At high moisture content, the protons directly attached to the carbon chains of molecules seemed to be immobile, those in the hydroxyl group to be relatively mobile, and those in water to be more mobile.Powders stored at a temperature above T_g were caked after cooling to room temperature. Less

近年来，玻璃化转变引起了食品科学家的极大兴趣，因为许多与食品制造和保存相关的现象都可以用玻璃化转变的概念来系统地解释：例如，食品材料在玻璃态下比在橡胶态下更好地保持其物理和化学稳定性。许多食品的玻璃化转变温度 T_g 已通过热分析（例如差示扫描量热法 (DSC)）测定。然而，热分析不提供有关分子迁移率的信息。在这项研究中，通过脉冲核磁共振分析了玻璃状和橡胶状材料之间分子迁移率的差异，脉冲核磁共振可以通过分析质子的弛豫行为、水对分子迁移率的影响来检测系统中组分的迁移率。此外，还研究了玻璃化转变对食品粉末的两个重要质量变化——结块和颜色变化的影响。通过DSC测定了食品的玻璃化转变温度T_g。由于水的塑化作用，所检测食品的 T 值随着水分含量的增加而降低。对于小麦面筋，颜色变化AE的临界点可以视为对应于玻璃到橡胶的转变点。面筋的 DSC 数据也支持面筋在颜色变化临界点以上处于玻璃态。所检测的食品的吸水等温线与许多食品材料相似，呈 S 形；吸附水的量在玻璃到橡胶的转变点以上急剧增加。水吸附率在水活度0.5-0.6附近取最大值。NMR的FID（自由感应衰减）通过高斯、指数和高斯线形的两个或三个分量的组合令人满意地描述。 M_2显示一或两个转变温度。在低水分含量时，固定组分的百分比占主导地位，但随着水分含量的增加而减少。在高水分含量下，直接附着在分子碳链上的质子似乎是固定的，羟基中的质子相对流动，而水中的质子则更容易流动。在T_g以上温度下储存的粉末在冷却至室温后结块。较少的