氨基酸对淀粉结构形貌及热致相变行为的影响

Effects of Amino Acids on Structures,Morphologies and Heat-induced Phase Transformation of Starches

以玉米淀粉为研究对象,采用传统仪器表征技术和分子动力学模拟相结合的方式,系统研究了氨基酸对淀粉结构形貌及热致相变行为的影响。研究结果表明,酸性谷氨酸和碱性赖氨酸使体系pH值由7.13分别变为3.27和9.72,较强的酸碱性一定程度破坏淀粉颗粒形貌及内部结构,使颗粒表面变粗糙及内部相对结晶度提高。在氨基酸/淀粉共混溶液体系中,氨基酸分子与淀粉分子的氢键相互作用随着氨基酸含量的增大逐渐增强。三种氨基酸在不同含量条件下均能抑制淀粉分子糊化,其中含量为10%的甘氨酸、赖氨酸和谷氨酸使淀粉的糊化峰值温度分别提高了3.71℃、6.00℃和5.58℃。分子动力学模拟技术为氨基酸影响淀粉分子相变行为的作用机制提供了有力的数据。分析结果表明,氨基酸分子通过影响淀粉分子周围水分子的分布,导致体系中与淀粉分子发生氢键相互作用的水分子数目减少,使淀粉构象稳定性提高,进而抑制淀粉的溶胀和糊化等相变行为。

In this work, corn starch was used as model material and the effects of amino acids on its morphology structure and phase transformations were systematically studied with a combination of traditional characterization techniques and molecular dynamics simulation.The results showed that the pH values were significantly changed from 7.13 to 3.27 and 9.72 by addition of acid glutamic acid and alkaline lysine, respectively. The amorphous areas of starch granules were damaged when treated by the strong acidic or alkaline condition of non-neutral amino acid solutions, which resulted in the rougher granule appearance and an increased in relatively crystalline content. In the blending system of amino acid/starch, the hydrogen bond interactions between starch molecules and amino acid molecules were gradually enhanced with an increased content of amino acid. The gelatinization of starch was inhibited by three amino acids at different contents. The peak gelatinization temperature of starch was increased by 3.71 ℃, 6.00 ℃ and 5.58 ℃ by 10% glycine, lysine and glutamate, respectively.Moreover, molecular dynamics simulation showed that the number of water molecules interacting with starch molecules through hydrogen bonding was reduced by amino acid molecules via affecting the distribution of water molecules around starch molecules, which induced a more stable structure of starch and further inhibited starch swelling and gelatinization.