缠结凝聚态对淀粉回生调控机制的研究

Starch retrogradation directly affects the quality, acceptability and shelf life of starch-based foods. However, it has still been investigated and explored stage that how to accurately control the degree of starch retrogradation to produce the expectant quality of starch-based foods. Based on food chemistry and polymer condensed matter physics, on the premise of ensuring the integrated short-range structure of Amylose (Am) and Amylopectin (Ap), hydrogen bond forming double helix spatial conformation of Am and Ap in starch particle will be broken by optimal shearing force to unlock the entanglement points between molecular chains of Am and Ap to form single molecular chains containing short-range structure (disentanglement). Then, critical overlap concentration (c*) will be as reference, three condensed matters of single-chain, pauci-chain and multi-chain starch particles will be prepared by spraying-freeze-drying to make the molecular chains of Am and Ap entangled again by hydrogen bond and Van der Waals'force(re-entanglement). Finally, the effects of the chain structural characteristics and intermolecular forces of Am and Ap on the entanglement of their chains under different concentrations will be studied and the character of entanglement point between the molecular chains of Am and Ap. The entanglement model of starch condensed matter will be established and the effect of different starch condensed matters on the crystallization morphology and dynamics will be clarified. The regulatory mechanism of the concentration on starch retrogradation will be established to provide effective theoretical basis regulating and producing the expectant quality of starch-based foods.

淀粉回生直接影响淀粉类食品品质、可接受性和货架期，但如何准确控制淀粉回生发生的程度以生产预期淀粉类食品品质尚处于研究探索阶段。本项目基于食品化学和高分子凝聚态物理学，在保证直链淀粉（Am）与支链淀粉(Ap)近程结构完整的前提下，采用适合的剪切力将淀粉原有的形成Am和Ap双螺旋空间构象的氢键断裂，使Am和Ap分子链缠结位点被解开而形成具有近程结构的单一分子链（解缠结）；其次，以临界交叠浓度c*为基准，采用喷雾-冷冻升华法制备单链、寡链和多链三种淀粉凝聚态，使Am和Ap通过氢键和范德华力使单一分子链重新缠结（再缠结）；最后，研究在不同浓度条件下Am和Ap分子链结构特性和分子间作用力对其分子链缠结特性的影响，揭示Am和Ap分子链段间的缠结位点特性，构建淀粉凝聚态缠结模型，阐明不同淀粉凝聚态对淀粉结晶形态和动力学的影响，建立浓度对淀粉回生调控机制，为调控生产预期淀粉类食品品质提供有效的理论依据。

淀粉回生直接影响淀粉类食品品质、可接受性和货架期，但如何准确控制淀粉回生发生的程度以生产预期淀粉类食品品质尚处于研究探索阶段。本项目基于食品化学和高分子凝聚态物理学，利用阴离子交换色谱、高效静态和动态流变仪、DSC、XRD、傅里叶变换红外光谱、低场核磁共振、透射电子显微镜等现代化仪器，首先分别确定谷物类淀粉（玉米、小麦、大米和糯米）和根茎类淀粉（葛根、藕、红薯和土豆）的缠结浓度ce，并基于缠结浓度ce系统研究淀粉缠结浓度对淀粉物化性能及成膜特性的影响，从而阐释缠结浓度ce对淀粉内部凝聚态结构影响的机理；其次，以缠结浓度ce为基准点，研究在不同浓度条件下Am和Ap分子链结构特性和分子间作用力对其分子链缠结特性的影响，揭示Am和Ap分子链段间的缠结位点特性，构建淀粉凝聚态缠结模型；最后，阐明不同淀粉凝聚态对淀粉结晶形态和动力学的影响，建立缠结浓度对淀粉回生调控机制。研究结果表明，玉米、小麦、大米、糯米淀粉的ce 值分别为1.69、1.38、0.36 和0.33%。葛根淀粉、藕淀粉、红薯淀粉和土豆淀粉溶液的缠结浓度ce分别为1.56%、0.60%、0.54%和0.43%。缠结浓度ce对葛根淀粉、土豆淀粉和大米淀粉溶液网络结构的形成影响较大。缠结浓度ce对根茎类淀粉溶液的G'、G"、复合粘度η*影响显著，对大米和糯米淀粉溶液的G′和η*值影响显著。当溶液浓度≥ce时，所有谷物和根茎类淀粉的糊化温度大幅度提高，说明缠结浓度ce对与淀粉溶液的热力学性质影响显著。缠结浓度ce对所有淀粉溶液的1045 cm−1/1022 cm−1的峰强度比值有很显著的影响。随着淀粉溶液浓度的增加，糊化淀的T2值逐渐减小，在接近缠结浓度ce，老化淀粉溶液的T2值显著减小。淀粉溶液不论是老化还是在糊化状态下，随着淀粉溶液浓度的的增加，缠结网络结构的形成，淀粉结构愈加紧密。因此，缠结浓度ce对溶液中淀粉凝聚态网络结构的形成具有关键性的作用，由此建立了淀粉Am和Ap分子链段缠结浓度及其模型，为淀粉类食品加工过程中如何调控浓度以生产预期淀粉类食品品质提供有效的理论依据。