Understanding starch granule architecture and its relationship to starch functionality

尽管关于淀粉生物合成和结构的知识取得了重大进展，但与淀粉质体中晶体形成的起始和不同植物来源淀粉颗粒的特定结构有关的问题仍然存在。我们研究的目标是了解淀粉颗粒的结构，并将所获得的知识与淀粉在多组分食物基质中的行为联系起来。我们建议用碘作为标记物来研究淀粉颗粒结构，这是我们最近开发的一种新技术。使用碘作为工具，我们证明了在天然颗粒状线性聚合物淀粉中的迁移性，其聚合度（dp）在水分含量低至8%时高达35，在水分含量为20%时高达dp 105。我们进一步发现，在水分含量低于20%时，不同植物源淀粉的碘结合特性有显著差异。这些观察结果表明，在天然颗粒中，硬脂不受限制的线性聚合物片段可以自由移动，并与碘形成单一的螺旋复合物，在低水分含量下表现出特有的颜色。通过将碘络合技术与其他控制淀粉的酶和化学修饰相结合，我们建议进一步推断来自不同植物来源的淀粉的颗粒结构。拟议的研究将提高我们对自然界中最普遍的聚合物之一的理解。此外，本研究对淀粉在食品中的应用和使用具有重要意义。我们实验室的研究表明，在有限的水分条件下，根据加工条件的不同，存在控制淀粉颗粒膨胀、糊化和聚合物重排的动力学限制。了解颗粒结构将有助于更好地理解颗粒内的聚合物如何分散、相分离并在冷却和储存时形成后续复合物。我们实验室的初步数据表明，调节加工条件可以影响产品中随后形成的网络，我们可以改变淀粉在消化过程中分解为葡萄糖的速度，即改变血糖反应。

Despite significant advances in knowledge about starch biosynthesis and structure, questions related to the initiation of crystal formation in the amyloplast and the specific architecture of the starch granule from different botanical sources, still persist. The goal of our research is to understand the architecture of starch granules and relate the knowledge gained to the behaviour of starch in multi-component food matrices. We propose to investigate starch granule architecture using iodine as a marker on native, granular dry starch, a novel technique we developed recently. Using iodine as a tool, we demonstrated mobility in native granular starches of linear polymers with degree of polymerization (dp) of up to 35 at moisture contents as low as 8% and up to dp 105 at a moisture content of 20 %. We further showed that starches from different botanical sources had significantly different iodine binding properties at moisture contents below 20%. These observations suggest that in native granules, there are stearically unrestricted segments of linear polymers that are free to move and form a single helical complex with iodine, exhibiting characteristic color at low moisture contents. By combining the iodine complexing technique with other controlled enzymatic and chemical modifications to the starch, we propose to further deduce the granular architecture of starches from different botanical sources. The proposed research will improve our understanding on one of the most prevalent polymers in nature. Moreover, this research has relevance in the application and uses of starches in foods. Research from our laboratory has shown that under limited moisture conditions, depending on the processing conditions, there is kinetic limitation that governs starch granule swelling, gelatinization and polymer rearrangement. Understanding granule architecture will aid in better understanding how polymers within granules disperse, phase-separate and form subsequent complexes upon cooling and storage. Preliminary data from our laboratory have shown that modulating the processing conditions can influence the subsequent network formed in the product and we can alter the rate of breakdown of starch into glucose during digestion, i.e., alter the glycemic response.