Department of Food Science, University of Guelph, Guelph, Ontario, Canada N1G 2W1.
Carbohydr Res. 2011 Nov 8;346(15):2482-90. doi: 10.1016/j.carres.2011.08.017. Epub 2011 Aug 27.
Iodine has been used as an effective tool for studying both the structure and composition of dispersed starch and starch granules. In addition to being employed to assess relative amylose contents for starch samples, it has been used to look at the molecular mobility of the glucose polymers within intact starch granules based on exposure to iodine vapor equilibrated at different water activities. Starches of different botanical origin including corn, high amylose corn, waxy corn, potato, waxy potato, tapioca, wheat, rice, waxy rice, chick pea and mung bean were equilibrated to 0.33, 0.75, 0.97 water activities, exposed to iodine vapor and then absorbance spectra and LAB color were determined. In addition, a new iodine quantification method sensitive to <0.1% iodine (w/w) was employed to measure bound iodine within intact granular starch. Amylose content, particle size distribution of granules, and the density of the starch were also determined to explore whether high levels of long linear glucose chains and the surface area-to-volume ratio were important factors relating to the granular iodine binding. Results showed, in all cases, starches complexed more iodine as water content increased and waxy starches bound less iodine than their normal starch counterparts. However, much more bound iodine could be measured chemically with waxy starches than was expected based on colorimetric determination. Surface area appeared to be a factor as smaller rice and waxy rice starch granules complexed more iodine, while the larger potato and waxy potato granules complexed less than would be expected based on measured amylose contents. Corn, high amylose corn, and wheat, known to have starch granules with extensive surface pores, bound higher levels of iodine suggesting pores and channels may be an important factor giving iodine vapor greater access to bind within the granules. Exposing iodine vapor to moisture-equilibrated native starches is an effective tool to explore starch granule architecture.
碘已被用作研究分散淀粉和淀粉颗粒结构和组成的有效工具。除了用于评估淀粉样品的相对直链淀粉含量外，它还被用于根据暴露于不同水分活度平衡的碘蒸气来研究完整淀粉颗粒内葡萄糖聚合物的分子迁移率。不同植物来源的淀粉，包括玉米、高直链玉米、蜡质玉米、马铃薯、蜡质马铃薯、木薯、小麦、大米、蜡质大米、鹰嘴豆和绿豆，平衡至 0.33、0.75 和 0.97 的水分活度，暴露于碘蒸气后，测定吸光度和 LAB 颜色。此外，还采用了一种对<0.1%碘（w/w）敏感的新碘定量方法来测量完整颗粒淀粉内的结合碘。还测定了直链淀粉含量、颗粒粒径分布和淀粉密度，以探讨长直链葡萄糖链的高含量和表面积与体积比是否是与颗粒碘结合相关的重要因素。结果表明，在所有情况下，随着水分含量的增加，淀粉结合的碘越多，蜡质淀粉结合的碘越少。然而，与比色测定相比，用化学方法可以测量到更多的结合碘。表面积似乎是一个因素，因为较小的大米和蜡质大米淀粉颗粒结合了更多的碘，而较大的马铃薯和蜡质马铃薯颗粒结合的碘则少于根据直链淀粉含量测量所预期的量。玉米、高直链玉米和小麦，已知其淀粉颗粒具有广泛的表面孔隙，结合了更高水平的碘，这表明孔隙和通道可能是碘蒸气更容易进入颗粒内部结合的重要因素。将碘蒸气暴露于水分平衡的天然淀粉是探索淀粉颗粒结构的有效工具。
