方便食品在储存时倾向于改变其质量和质地。赋予质地的食物成分通常是富含淀粉的成分,如面食或米饭。淀粉随时间变化,温度和含水量,这改变了产品的性能。监控这些转变,这与淀粉链段的流动性变化有关,可以优化含有多种成分的食品的质量。为了做到这一点,我们应用了一种简单有效的原位13C固态幻角旋转(MAS)NMR方法,基于两种不同的极化传输方案,交叉极化(CP)和不敏感核通过极化转移(INEPT)增强。CP和INEPT转移的效率在很大程度上取决于链段的迁移率-CH键重新取向的时间尺度和有序参数。刚性结晶或无定形淀粉链产生CP峰,而可移动的糊化淀粉链显示为INEPT峰。比较基于CP和INEPT的13C固态MASNMR实验,可以深入了解糊化的进展,和其他淀粉转化,通过13C化学位移同时报告刚性和移动淀粉链的原子分辨率。结合1H固态MASNMR,关于低浓度存在的其他食物成分的补充信息,如脂质和蛋白质,可以获得。我们展示了基于淀粉的产品和商业面食作为温度和储存的函数的方法。
Convenience food products tend to alter their quality and texture while stored. Texture-giving food components are often starch-rich ingredients, such as pasta or rice. Starch transforms depending on time, temperature and water content, which alters the properties of products. Monitoring these transformations, which are associated with a change in mobility of the starch chain segments, could optimize the quality of food products containing multiple ingredients. In order to do so, we applied a simple and efficient in situ 13 C solid-state magic angle spinning (MAS) NMR approach, based on two different polarization transfer schemes, cross polarization (CP) and insensitive nuclei enhanced by polarization transfer (
INEPT). The efficiency of the CP and
INEPT transfer depends strongly on the mobility of chain segments-the time scale of reorientation of the CH-bond and the order parameter. Rigid crystalline or amorphous starch chains give rise to CP peaks, whereas mobile gelatinized starch chains appear as
INEPT peaks. Comparing 13 C solid-state MAS NMR experiments based on CP and
INEPT allows insight into the progress of gelatinization, and other starch transformations, by reporting on both rigid and mobile starch chains simultaneously with atomic resolution by the 13 C chemical shift. In conjunction with 1 H solid-state MAS NMR, complementary information about other food components present at low concentration, such as lipids and protein, can be obtained. We demonstrate our approach on starch-based products and commercial pasta as a function of temperature and storage.