Ministry of Education Engineering Research Center of Starch & Protein Processing, Guangdong Province Key Laboratory for Green Processing of Natural Products and Product Safety, School of Food Science and Engineering, South China University of Technology, Guangzhou 510640, China.
Department of Chemical Engineering, University of Bath, Bath BA2 7AY, United Kingdom.
Int J Biol Macromol. 2024 Oct;277(Pt 2):134283. doi: 10.1016/j.ijbiomac.2024.134283. Epub 2024 Jul 30.
Starch degradation often coincides with its chemical modification, and understanding how chemical modification influences starch degradation is vital for determining the properties of the resultant modified products. This work investigates the effect of oxidation on starch molecular degradation, examining factors such as oxidation degree, reaction kinetics, and degradation patterns during 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-mediated starch oxidation under varying conditions, including reaction time, pH, temperature, and concentrations of NaBr, TEMPO, and NaClO. Results emphasize that extended reaction durations primarily lead to β-elimination, causing α-1,4 linkage cleavages. pH 8.5 favored non-selective oxidation, while pH 11 enhanced β-elimination, both slowing the reaction rate and severely damaging starch chains (M of 8.8 × 10 g/mol and 7.2 × 10 g/mol, respectively). Elevated temperature from 0 to 30 °C significantly expedited both selective and non-selective oxidation, dramatically reducing molecular mass to 8.1 × 10 g/mol. Increasing concentrations of NaBr and TEMPO boost the reaction rate with minimal impact on molecular mass. Meanwhile, increasing NaClO concentration from 0.2 to 2.2 mmol/g-starch not only affects the reaction rate but also reinforces β-elimination, enhancing molecular degradation. This study is insightful for starch modification to achieve desired oxidation levels and chain lengths by controlling reaction conditions, offering potential advancements in oxidized starch-based materials like nano micelles.
淀粉的降解通常与化学修饰同时发生，了解化学修饰如何影响淀粉的降解对于确定所得改性产物的性质至关重要。本工作研究了氧化对淀粉分子降解的影响，考察了氧化度、反应动力学以及在不同条件下，包括反应时间、pH 值、温度以及 NaBr、TEMPO 和 NaClO 的浓度下，TEMPO 介导的淀粉氧化过程中的降解模式等因素。结果强调，延长反应时间主要导致 β-消除，导致 α-1,4 键断裂。pH 值为 8.5 有利于非选择性氧化，而 pH 值为 11 增强了 β-消除，这两种情况都降低了反应速率并严重破坏了淀粉链（M 值分别为 8.8×10g/mol 和 7.2×10g/mol）。从 0 到 30°C 的温度升高显著加速了选择性和非选择性氧化，使分子量急剧降低至 8.1×10g/mol。NaBr 和 TEMPO 浓度的增加提高了反应速率，对分子量的影响最小。同时，从 0.2 到 2.2mmol/g-淀粉增加 NaClO 浓度不仅影响反应速率，还加强了β-消除，增强了分子降解。本研究对于通过控制反应条件来实现所需的氧化水平和链长的淀粉改性具有重要意义，为基于氧化淀粉的纳米胶束等材料的潜在发展提供了参考。
